WO2010007363A2

WO2010007363A2 - Preparation of fluorine-labelled compounds

Info

Publication number: WO2010007363A2
Application number: PCT/GB2009/001742
Authority: WO
Inventors: Veronique Gouverneur; Romain Bejot
Original assignee: Isis Innovation Limited
Priority date: 2008-07-15
Filing date: 2009-07-14
Publication date: 2010-01-21
Also published as: GB0812923D0; WO2010007363A3

Abstract

The invention relates to a process for producing a fluorine-labelled compound, the process comprising: (a) treating a compound of formula (I) wherein R¹, R² and the C(H) group to which R¹ and R² are bonded together form a moiety to be labelled with fluorine; and the fluorous tag is a group of formula (II) wherein Rf is a straight-chained or branched C_4-I2 perfluoroalkyl group; and L is a single bond, -alk-, -arylene-, -alk-arylene-, alk-X-, -arylene-X-, -alk-arylene-X, -alk- X-arylene-, -alk-X-arylene-X-, -arylene-alk-, -arylene-X-alk-, -arylene-alk-X- or - arylene-X-alk-X-, wherein X is N(R"), O, S, C(O) or C(O)N(R") and wherein alk is unsubstituted or substituted C_1-10alkylene which is optionally interrupted by N(R"), O, S, C(O), C(O)N(R") or arylene, wherein R" is C_1-6alkyl or aryl; with [ⁿF], wherein ⁿF is ¹⁸F or ¹⁹F, thereby fluorinating and detagging the compound of formula (I) to produce a fluorine-labelled compound of formula (III) The invention further relates to compounds of formula (I), a process for producing such compounds, and a combination product which comprises the two reactants used in that process.

Description

PREPARATION OF FLUORINE-LABELLED COMPOUNDS

Field of the Invention

The invention relates to a process for producing fluorine-labelled compounds, particularly compounds labelled with ¹⁸F for use in Positron Emission Tomography (PET). The invention also relates to tagged precursor compounds for use in the process, and to a process for producing the tagged precursors.

Background of the Invention Positron Emission Tomography (PET) is a nuclear imaging technique of ever increasing importance in diagnostic medicine today. It allows non-invasive diagnostic examination of subjects via the detection of pairs of gamma rays indirectly emitted from positron emitting radioisotopes, producing a 3D image of a functional process in vivo. PET requires the use of a positron emitting radionuclide to trace a physiological or biochemical process in tissue. In order to take a PET scan, a short half-life radionuclide which decays through positron emission is incorporated into a metabolically active molecule. This is injected into the patient and allowed to circulate round the body in order to obtain its optimum biodistribution. The subject is then placed within the PET scanner. A relatively accurate image can be drawn of the radiotracer distribution within the area of interest.

PET most commonly utilizes the radioactive forms of carbon (¹¹C), nitrogen (¹³N), oxygen (¹⁵O) and fluorine (¹⁸F). Use of these isotopes allows the labelling of many different substrates without altering the biological activity. The half lives of these nuclei are relatively short, which poses a time-scale problem for radio-chemists and can leave little room for manoeuvre between introducing the radioisotope into the tracer, and conducting the PET scan. Of these isotopes F has the most convenient (longest) half life, of 109.7 minutes.

Positron emitting ¹⁸F can be reliably produced on large scale as ¹⁸F^". This can then be used to fluorinate in its nucleophilic fluoride form, or it can undergo further manipulation to convert it to one of a number of electrophilic fluorinating reagents. The most common of these electrophilic reagents is [¹⁸F]F₂. After its initial production, electrophilic fluorination with [¹⁸F]F₂ can be performed directly, the most common reactions being electrophilic aromatic substitutions of trialkyl tin or mercury groups. The major drawback of electrophilic radiofluorination is that only one of the two atoms in elemental fluorine is positron emitting F, and so use of [ F]F₂ either to directly fluorinate a species or to produce other fluorination reagents can only lead to a theoretical maximum radiochemical yield of 50%. This, combined with a low specific activity, mean electrophilic radiofluorination is only used when a nucleophilic method is not feasible.

The majority of nucleophilic fluorinations utilize the no-carrier added ¹⁸F- fiuoride ion. Once the nucleophilic source of ¹⁸F^" has been produced, fluorination of a compound typically involves the activation of the no-carrier added fluoride by the addition of a cryptand (typically Kryptofix-222) to form a 'naked fluoride ion' as a K[¹⁸F]F-K₂₂₂ complex. Typically, this is then heated with the desired substrate at a temperature most often in the range of 80°C to 160°C.

An important aspect of radiopharmaceutical production requiring consideration by PET chemists is the method of purification to be adopted. Lengthy purification steps need to be avoided due to the resultant decrease in non-decay corrected radiochemical yield, yet the method of choice must be effective enough to ensure a high level of radiochemical purity.

In the majority of radiolabelling procedures, very large excesses of starting material are used relative to the ¹⁸F^" source. In the case of [¹⁸F]fluorodeoxyglucose ([¹⁸F]-FDG), the most widely used PET imaging agent in clinical oncology, the target product is made along side excess D-glucose as well as a range of other degradation products from undesirable side reactions, hi this specific case these products are not harmful if injected into a subject, however this may not be the case for other radiotracers. Furthermore, the presence of unlabelled starting material and decayed substrate can compete with the radiolabeled tracer for the in vivo target, resulting in reduced image quality. The large amount of unreacted starting material remaining, and additional side products, must therefore be separated from the successfully labelled substrate. At present there are various methods of purification which can be adopted.

HPLC (High-Performance Liquid Chromatography) is very effective at giving highly purified products. However, whilst HPLC is a very powerful technique for separation it presents several problems for the preparation of radiolabeled compounds. First, it is relatively time consuming. Due to the very large excess of unreacted starting material remaining in the crude reaction mixture, multiple HPLC runs can be required to obtain the pure target product. HPLC purification typically takes between 15 and 30 minutes, which in the case of radiolabeled compounds results in a significant loss of radioactivity due to decay. Second, the purified radiolabeled compound is diluted to volumes that are too large for subsequent reactions, and for reaction intermediates an additional concentration step is required. Thirdly, HPLC is difficult to automate and any procedure involving HPLC therefore requires manual handling/supervision or highly complicated equipment. Finally, HPLC equipment takes up relatively large space compared with other equipment used for radiolabelling, which restrains the number of productions rigs and other equipment that can be placed in a hot-cell.

Another method of purification that can be adopted is chromatography by means of cartridges/Sep-Pak. This technique is based on the same principles as HPLC, but rather than using a highly pressurised column this technique utilises a small cartridge containing a suitable stationary phase with elution of a solvent using mild pressure. Whilst this method is less time consuming and space demanding than HPLC it represents several of the same problems to radiosynthesis as HPLC. First, the isolated radiolabeled compound is usually obtained in diluted form and hence further concentration is required for reaction intermediates. Second, the method involves a number of technical steps, i.e. diluting the product mixture in a suitable solvent (usually aqueous phase), passing the diluted mixture through the cartridge washing the cartridge with a suitable solvent (usually water) and third eluting the radiolabeled compound in a suitable solvent (usually an organic solvent). While this is easier to automate than HPLC, the additional steps introduce significant extra complication to any automated equipment. Fourth, as the cartridge usually has to be washed with an aqueous solution as part of the procedure, a drying step is often required. Finally, the overall procedure is relatively time consuming and hence results in significant loss of radioactivity due to radioactive decay.

Purification by means of conventional distillation of radiolabeled compounds is also often problematic. Distillation is usually carried out by heating a reaction vessel containing the product under reduced pressure or under a stream of an inert gas such as nitrogen, argon or helium. Successful distillation requires heating slightly above the boiling point of the solvent, lower temperature gives low distillation rate and a higher temperature often results in vigorous boiling with the effect that parts of the crude mixture are carried over with the product. It is also difficult to collect the radiolabeled compound effectively, as the inert gas stream must be sufficient to carry the radiolabeled compound over to a collecting vessel. However, if the gas stream is too strong, condensation efficiency is reduced as the gas carries the radiolabeled compound beyond the collection vessel. As a result, distillation yields are difficult to make reproducible, the procedure is time consuming and automation is complicated. Since the equipment required for distillation typically has a relatively large volume compared with the volume of the reaction mixture, losses in the process are significant. Finally, as the procedure entails prolonged heating of reaction mixtures decomposition is often a problem, particularly with labile radiolabeled compounds such as acid halides.

Recent developments in methods for the production of the radiotracer [¹⁸F]FDG have focused on a solid-phase synthesis technique. The [¹⁸F]FDG precursor is attached to the surface of a polymer resin and remains bound until it is selectively fluorinated, at which point it detaches. Heterogeneous phase reactions however do not have as favourable reaction kinetics as a homogeneous process.

Also, considerable time and effort has to be employed in the design and synthesis of the precursor-bonded resin for each individual reaction type.

There therefore exists a continuing need to develop improved methods for the production and purification of fluorinated compounds.

Summary of the Invention

The inventors have found that compounds hosting a hydroxyl functionality can be tagged successfully using fluorous sulfonyl species. Such compounds include mono-saccharides, amino acids and other organic compounds, including compounds supporting functional groups such as azide, epoxide and terminal alkyne functional groups. Subsequent detagging has been achieved via a nucleophilic fluorination reaction. The detagged, fluorinated product can be readily separated from any fluorous material (and thereby purified) using, for instance, a Fluorous Solid Phase Extraction (FSPE) procedure.

This technology facilitates the rapid synthesis and purification of ¹⁸F-labelled species via a nucleophilic fluorination process using positron-emitting ¹⁸F^". The method can also be used to synthesise and purify ¹⁹F-labelled species.

If desired, further reactions of the purified fluorinated species can be performed. For instance, the fluorinated species can be coupled via a functional group to another molecule (e.g. to a molecule having an affinity for a biological target), for instance via a click reaction or via a nucleophilic attack of an amine onto an epoxide.

The invention provides a process for producing a fluorine-labelled compound, the process comprising: (a) treating a compound of formula (I)

wherein:

R¹, R² and the C(H) group to which R¹ and R² are bonded together form a moiety to be labelled with fluorine; and the fluorous tag is a group of formula (II)

wherein Rf is a straight-chained or branched C_4-I2 perfluoroalkyl group; and

L is a single bond, -alk-, -arylene-, -alk-arylene-, alk-X-, -arylene-X-, -alk- arylene-X, -alk-X-arylene-, -alk-X-arylene-X-, -arylene-alk-, -arylene-X-alk-, -arylene-alk-X- or -arylene-X-alk-X-, wherein X is N(R"), O, S, C(O) or C(O)N(R") and wherein alk is unsubstituted or substituted C_MO alkylene which is optionally interrupted by N(R"), O, S, C(O), C(O)N(R") or arylene, wherein R" is Ci_-6 alkyl or aryl; with [ⁿF]^", wherein ⁿF is ¹⁸F or ¹⁹F, thereby fluorinating and detagging the compound of formula (I) to produce a fluorine-labelled compound of formula (III)

wherein R¹ and R² are as defined above for formula (I). Typically, the step of treating the compound of formula (I) with [ⁿF]^" is carried out in the presence of a solvent.

Typically, the process further comprises: (b) separating the compound of formula (III) from one or more fluorous compounds which comprise Rf.

Typically, step (b) comprises separating the compound of formula (III) from the one or more fluorous compounds by Fluorous Solid Phase Extraction (FSPE).

The compounds of formula (I) comprising the fluorous tag are new.

Accordingly, in another aspect, the invention provides a compound of formula (I)

wherein:

R¹, R² and the C(H) group to which R¹ and R² are both bonded together form a moiety to be labelled with flourine; and the fluorous tag is a group of formula (II)

wherein Rf is a straight-chained or branched C_4-12 perfluoroalkyl group; and

L is a single bond, -alk-, -arylene-, -alk-arylene-, alk-X-, -arylene-X-, -alk-arylene-X, -alk-X-arylene-, -alk-X-arylene-X-, -arylene-alk-, -arylene-X-alk-, -arylene-alk-X- or -arylene-X-alk-X-, wherein X is N(R"), O, S, C(O) or C(O)N(R") and wherein alk is unsubstituted or substituted Ci_-I0 alkylene which is optionally interrupted by N(R"), O, S, C(O), C(O)N(R") or arylene, wherein R" is C_1-6 alkyl or aryl. In another aspect, the invention provides a process for producing a compound of formula (I)

wherein: R¹, R² and the C(H) group to which R¹ and R² are bonded together form a moiety to be labelled with fluorine; and the fluorous tag is a group of formula (II)

wherein Rf is a straight-chained or branched C_4-I2 perfluoroalkyl group; and L is a single bond, -alk-, -arylene-, -alk-arylene-, alk-X-, -arylene-X-, -alk- arylene-X, -alk-X-arylene-, -alk-X-arylene-X-, -arylene-alk-, -arylene-X-alk-, -arylene-alk-X- or -arylene-X-alk-X-, wherein X is N(R"), O, S, C(O) or C(O)N(R") and wherein alk is unsubstituted or substituted C_1-I0 alkylene which is optionally interrupted by N(R"), O, S, C(O), C(O)N(R") or arylene, wherein R" is Ci_-6 alkyl or aryl; which process comprises treating a compound of formula (IV)

C(H)-OH (IV)

R² wherein R¹ and R² are as defined for formula (I), with a compound of formula (V)

wherein Rf and L are as defined for formula (II); and either y is 1 and X' is a halo group, or y is 2 and X' is O.

In another aspect, the invention provides a combination product comprising: (a) a compound of formula (IV)

\

C(H)-OH (IV)

R² wherein R¹, R² and the C(H) group to which R¹ and R² are bonded together form a moiety to be labelled with fluorine; and (b) a compound of formula (V)

wherein Rf is a straight-chained or branched C_4-12 perfluoroalkyl group; and L is a single bond, -alk-, -arylene-, -alk-arylene-, alk-X-, -arylene-X-, -alk- arylene-X, -alk-X-arylene-, -alk-X-arylene-X-, -arylene-alk-, -arylene-X-alk-, -arylene-alk-X- or -arylene-X-alk-X-, wherein X is N(R"), O, S, C(O) or C(O)N(R") and wherein alk is unsubstituted or substituted Ci_-I0 alkylene which is optionally interrupted by N(R"), O, S, C(O), C(O)N(R") or arylene, wherein R" is Cj_-6 alkyl or aryl; and either y is 1 and X' is a halo group, or y is 2 and X' is O. Compounds (a) and (b) in the combination product of the invention may be reacted together to produce a tagged precursor compound of formula (I).

Brief Description of the Figures

Fig. l is a schematic illustration of a Fluorous Solid Phase Extraction (FSPE) process, which may be applied in the process of the present invention.

Fig. 2 is a flow diagram illustrating the preparation of K¹⁸F-Kryptofix, which may be used as the source of ¹⁸F^" in the process of the present invention.

Detailed Description of the Invention The following substituent definitions apply with respect to the compounds defined herein: A C_1-2O alkyl group is an unsubstituted or substituted, straight or branched chain saturated hydrocarbon radical. Typically it is C_1-10 alkyl, for example methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl or decyl, or Cj_-6 alkyl, for example methyl, ethyl, propyl, butyl, pentyl or hexyl, or C_1-4 alkyl, for example methyl, ethyl, i-propyl, n-propyl, t-butyl, s-butyl or n-butyl. When an alkyl group is substituted it typically bears one or more substituents selected from substituted or unsubstituted Ci_-20 alkyl, substituted or unsubstituted aryl (as defined herein), cyano, amino, C_1-I0 alkylamino, di(Ci.i₀)alkylamino, arylamino, diarylamino, arylalkylamino, amido, acylamido, hydroxy, oxo, halo, carboxy, ester, acyl, acyloxy, Ci_-20 alkoxy, aryloxy, haloalkyl, sulfonic acid, sulfhydryl (i.e. thiol, -SH), Ci_-I0 alkylthio, arylthio, sulfonyl, phosphoric acid, phosphate ester, phosphonic acid and phosphonate ester. Examples of substituted alkyl groups include haloalkyl, hydroxyalkyl, aminoalkyl, alkoxyalkyl and alkaryl groups. The term alkaryl, as used herein, pertains to a Ci_-20 alkyl group in which at least one hydrogen atom has been replaced with an aryl group. Examples of such groups include, but are not limited to, benzyl (phenylmethyl, PhCH₂-), benzhydryl (Ph₂CH-), trityl (triphenylmethyl, Ph₃C-), phenethyl (phenylethyl, Ph-CH₂CH₂-), styryl (Ph-CH=CH-), cinnamyl (Ph-CH=CH-CH₂-).

Typically a substituted Ci_-20 alkyl group carries 1, 2 or 3 substituents, for instance 1 or 2.

A C_4-I2 perfluoroalkyl group is a straight or branched chain saturated perfluorinated hydrocarbon radical having from 4 to 12 carbon atoms. "Perfluorinated" in this context means completely fluorinated such that there are no carbon-bonded hydrogen atoms replaceable with fluorine. Examples of C_4-I2 perfluoro alkyl groups are perfluorobutyl (C₄) (including perfluoro-n-butyl, perfluoro-sec-butyl and perfluoro-tert-butyl), perfluoropentyl (C₅), perfluorohexyl (C₆), perfluoroheptyl (C₇), perfluorooctyl (C₈), perfluorononyl (C₉), perfluorodecyl (C ₁₀), perfluoroundecyl (Cn) and perfluorododecyl (Ci₂), including straight chained and branched isomers thereof. A C_3-25 cycloalkyl group is an unsubstituted or substituted alkyl group which is also a cyclyl group; that is, a monovalent moiety obtained by removing a hydrogen atom from an alicyclic ring atom of a carbocyclic ring of a carbocyclic compound, which moiety has from 3 to 25 carbon atoms (unless otherwise specified), including from 3 to 25 ring atoms. Thus, the term "cycloalkyl" includes the sub-classes cycloalkyenyl and cycloalkynyl. Examples of groups Of C_3-25 cycloalkyl groups include C_3-20 cycloalkyl, C₃-_I5 cycloalkyl, C_3-10 cycloalkyl, C_3-7 cycloalkyl. When a C_3-25 cycloalkyl group is substituted it typically bears one or more substituents selected from Ci_-6 alkyl which is unsubstituted, aryl (as defined herein), cyano, amino, Ci_-I0 alkylamino, di(Ci-io)alkylamino, arylamino, diarylamino, arylalkylamino, amido, acylamido, hydroxy, oxo, halo, carboxy, ester, acyl, acyloxy, Ci_-20 alkoxy, aryloxy, haloalkyl, sulfonic acid, sulfhydryl (i.e. thiol, -SH), Ci_-I0 alkylthio, arylthio, phosphoric acid, phosphate ester, phosphonic acid and phosphonate ester and sulfonyl. Typically a substituted C_3-25 cycloalkyl group carries 1, 2 or 3 substituents, for instance 1 or 2.

Examples of C_3-25 cycloalkyl groups include, but are not limited to, those derived from saturated monocyclic hydrocarbon compounds, which C_3-25 cycloalkyl groups are unsubstituted or substituted as defined above: cyclopropane (C₃), cyclobutane (C₄), cyclopentane (C₅), cyclohexane (C₆), cycloheptane (C₇), methylcyclopropane (C₄), dimethylcyclopropane (C₅), methylcyclobutane (C₅), dimethylcyclobutane (C₆), methylcyclopentane (C₆), dimethylcyclopentane (C₇), methylcyclohexane (C₇), dimethylcyclohexane (C₈), menthane (Ci₀); unsaturated monocyclic hydrocarbon compounds: cyclopropene (C₃), cyclobutene (C₄), cyclopentene (C₅), cyclohexene (C₆), methylcyclopropene (C₄), dimethylcyclopropene (C₅), methylcyclobutene (C₅), dimethylcyclobutene (C₆), methylcyclopentene (C₆), dimethylcyclopentene (C₇), methylcyclohexene (C₇), dimethylcyclohexene (C₈); saturated polycyclic hydrocarbon compounds: thujane (Cio), carane (Ci₀), pinane (Ci₀), bornane (Ci₀), norcarane (C₇), norpinane (C₇), norbornane (C₇), adamantane (Ci₀), decalin (decahydronaphthalene) (Ci₀);

unsaturated polycyclic hydrocarbon compounds: camphene (C₁₀), limonene (Ci₀), pinene (Ci₀),

polycyclic hydrocarbon compounds having an aromatic ring: indene (Cg), indane (e.g., 2,3-dihydro-lH-indene) (Cg), tetraline (1,2,3,4-tetrahydronaphthalene) (Ci₀), acenaphthene (Ci₂), fluorene (Ci₃), phenalene (Ci₃), acephenanthrene (Ci₅), aceanthrene (Ci₆), cholanthrene (C₂₀).

A C_3-20 heterocyclyl group is an unsubstituted or substituted monovalent moiety obtained by removing a hydrogen atom from a ring atom of a heterocyclic compound, which moiety has from 3 to 20 ring atoms (unless otherwise specified), of which from 1 to 10 are ring heteroatoms. Preferably, each ring has from 3 to 7 ring atoms, of which from 1 to 4 are ring heteroatoms. When a C_3-20 heterocyclyl group is substituted it typically bears one or more substituents selected from Ci_-6 alkyl which is unsubstituted, aryl (as defined herein), cyano, amino, C_MO alkylamino, di(Ci- io)alkylamino, arylamino, diarylamino, arylalkylamino, amido, acylamido, hydroxy, oxo, halo, carboxy, ester, acyl, acyloxy, Ci_-20 alkoxy, aryloxy, haloalkyl, sulfonic acid, sulfhydryl (i.e. thiol, -SH), Ci_-I0 alkylthio, arylthio, phosphoric acid, phosphate ester, phosphonic acid and phosphonate ester and sulfonyl. Typically a substituted C_3-20 heterocyclyl group carries 1, 2 or 3 substituents, for instance 1 or 2.

Examples of groups of heterocyclyl groups include C_3-20heterocyclyl, C_5-20heterocyclyl, C_3-i₅heterocyclyl, C_5-i₅heterocyclyl, C_3-i₂heterocyclyl, Cs-^heterocyclyl, C_3-10heterocyclyl, Cs-ioheterocyclyl, C_3-7heterocyclyl, C₅-₇heterocyclyl, and Cs-_όheterocyclyl.

Examples of (non-aromatic) monocyclic C_3-20 heterocyclyl groups include, but are not limited to, those derived from: N₁ : aziridine (C₃), azetidine (C₄), pyrrolidine (tetrahydropyrrole) (C₅), pyrroline (e.g., 3-pyrroline, 2,5-dihydropyrrole) (C₅), 2H-pyrrole or 3H-pyrrole (isopyrrole, isoazole) (C₅), piperidine (C₆), dihydropyridine (C₆), tetrahydropyridine (C₆), azepine (C₇);

O₁: oxirane (C₃), oxetane (C₄), oxolane (tetrahydrofuran) (C₅), oxole (dihydrofuran) (C₅), oxane (tetrahydropyran) (C₆), dihydropyran (C₆), pyran (C₆), oxepin (C₇);

S₁: thiirane (C₃), thietane (C₄), thiolane (tetrahydrothiophene) (C₅), thiane (tetrahydrothiopyran) (C₆), thiepane (C₇);

O₂: dioxolane (C₅), dioxane (C₆), and dioxepane (C₇); O₃: trioxane (C₆);

N₂: imidazolidine (C₅), pyrazolidine (diazolidine) (C₅), imidazoline (C₅), pyrazolone (dihydropyrazole) (C₅), piperazine (C₆);

N₁Oi: tetrahydrooxazole (C₅), dihydrooxazole (C₅), tetrahydroisoxazole (C₅), dihydroisoxazole (C₅), morpholine (C₆), tetrahydrooxazine (C₆), dihydrooxazine (C₆), oxazine (C₆);

NiSi: thiazoline (C₅), thiazolidine (C₅), thiomorpholine (C₆); N₂Oi : oxadiazine (C₆);

O₁Si: oxathiole (C₅) and oxathiane (thioxane) (C₆); and, NiOiSi: oxathiazine (C₆). Examples of substituted (non-aromatic) monocyclic heterocyclyl groups include those derived from saccharides, in cyclic form, for example, furanoses (C₅), such as arabinofuranose, lyxofuranose, ribofuranose, and xylofuranse, and pyranoses (C₆), such as allopyranose, altropyranose, glucopyranose, mannopyranose, gulopyranose, idopyranose, galactopyranose, and talopyranose. Examples of C_3-20 heterocyclyl groups which are also aryl groups are described below as heteroaryl groups. An aryl group is a substituted or unsubstituted, monocyclic or bicyclic aromatic group which typically contains from 6 to 14 carbon atoms, preferably from 6 to 10 carbon atoms in the ring portion. Examples include phenyl, naphthyl, indenyl and indanyl groups. An aryl group is unsubstituted or substituted. When an aryl group as defined above is substituted it typically bears one or more substituents selected from C₁-C₆ alkyl which is unsubstituted (to form an aralkyl group), aryl which is unsubstituted, cyano, amino, C_1-I₀ alkylamino, di(Ci_-1o)alkylamino, arylamino, diarylamino, arylalkylamino, amido, acylamido, hydroxy, halo, carboxy, ester, acyl, acyloxy, Ci_-20 alkoxy, aryloxy, haloalkyl, sulfhydryl (i.e. thiol, -SH), C_1-I₀ alkylthio, arylthio, sulfonic acid, phosphoric acid, phosphate ester, phosphonic acid and phosphonate ester and sulfonyl. Typically it carries 0, 1, 2 or 3 substituents. A substituted aryl group may be substituted in two positions with a single Ci_-6 alkylene group, or with a bidentate group represented by the formula -X-Ci_-6 alkylene, or -X- C_1-6 alkylene-X-, wherein X is selected from O, S and NR, and wherein R is H, aryl or Ci_-6 alkyl. Thus a substituted aryl group may be an aryl group fused with a cycloalkyl group or with a heterocyclyl group. The term aralkyl as used herein, pertains to an aryl group in which at least one hydrogen atom (e.g., 1, 2, 3) has been substituted with a Ci_-6 alkyl group. Examples of such groups include, but are not limited to, tolyl (from toluene), xylyl (from xylene), mesityl (from mesitylene), and cumenyl (or cumyl, from cumene), and duryl (from durene).

The ring atoms of an aryl group may include one or more heteroatoms (as in a heteroaryl group). Such an aryl group (a heteroaryl group) is a substituted or unsubstituted mono- or bicyclic hetero aromatic group which typically contains from 6 to 10 atoms in the ring portion including one or more heteroatoms. It is generally a 5- or 6-membered ring, containing at least one heteroatom selected from O, S, N, P, Se and Si. It may contain, for example, 1, 2 or 3 heteroatoms. Examples of heteroaryl groups include pyridyl, pyrazinyl, pyrimidinyl, pyridazinyl, furanyl, thienyl, pyrazolidinyl, pyrrolyl, oxazolyl, oxadiazolyl, isoxazolyl, thiadiazolyl, thiazolyl, isothiazolyl, imidazolyl, pyrazolyl, quinolyl and isoquinolyl. A heteroaryl group may be unsubstituted or substituted, for instance, as specified above for aryl. Typically it carries 0, 1, 2 or 3 substituents. A C_1-20 alkylene group is an unsubstituted or substituted bidentate moiety obtained by removing two hydrogen atoms, either both from the same carbon atom, or one from each of two different carbon atoms, of a hydrocarbon compound having from 1 to 20 carbon atoms (unless otherwise specified), which may be aliphatic or alicyclic, and which may be saturated, partially unsaturated, or fully unsaturated. Thus, the term "alkylene" includes the sub-classes alkenylene, alkynylene, cycloalkylene, etc., discussed below. Typically it is C_1-I0 alkylene, for instance Ci_-6 alkylene. Typically it is C_1-4 alkylene, for example methylene, ethylene, i-propylene, n-propylene, t-butylene, s-butylene or n-butylene. It may also be pentylene, hexylene, heptylene, octylene and the various branched chain isomers thereof. An alkylene group may be unsubstituted or substituted, for instance, as specified above for alkyl. Typically a substituted alkylene group carries 1, 2 or 3 substituents, for instance 1 or 2.

In this context, the prefixes (e.g., Cj_-4, Ci_-7, Ci_-2O, C_2-7, C_3-7, etc.) denote the number of carbon atoms, or range of number of carbon atoms. For example, the term "Ci^alkylene," as used herein, pertains to an alkylene group having from 1 to 4 carbon atoms. Examples of groups of alkylene groups include Ci_-4 alkylene ("lower alkylene"), C_1-7 alkylene, C_1-Io alkylene and C_1-2O alkylene.

Examples of linear saturated Cj_-7 alkylene groups include, but are not limited to, -(CH₂)_n- where n is an integer from 1 to 7, for example, -CH₂- (methylene),

-CH₂CH₂- (ethylene), -CH₂CH₂CH₂- (propylene), and -CH₂CH₂CH₂CH₂- (butylene).

Examples of branched saturated Ci_-7 alkylene groups include, but are not limited to, -CH(CH₃)-, -CH(CH₃)CH₂-, -CH(CH₃)CH₂CH₂-, -CH(CH₃)CH₂CH₂CH₂-, -CH₂CH(CH₃)CH₂-, -CH₂CH(CH₃)CH₂CH₂-, -CH(CH₂CH₃)-, -CH(CH₂CH₃)CH₂-, and -CH₂CH(CH₂CH₃)CH₂-.

Examples of linear partially unsaturated Ci_-7 alkylene groups include, but is not limited to, -CH=CH- (vinylene), -CH=CH-CH₂-, -CH₂-CH=CH₂-, -CH=CH-CH₂-CH₂-, -CH=CH-CH₂-CH₂-CH₂-, -CH=CH-CH=CH-, -CH-CH-CH=CH-CH₂-, -CH=CH-CH=CH-CH₂-CH₂-, -CH=CH-CH₂-CH=CH-, and -CH=CH-CH₂-CH₂-CH=CH-.

Examples of branched partially unsaturated Ci_-7 alkylene groups include, but is not limited to, -C(CH₃)=CH-, -C(CH₃)=CH-CH₂-, and -CH=CH-CH(CH₃)-. Examples of alicyclic saturated C_1-7 alkylene groups include, but are not limited to, cyclopentylene (e.g., cyclopent-l,3-ylene), and cyclohexylene (e.g., cyclohex-l,4-ylene).

Examples of alicyclic partially unsaturated Ci_-7 alkylene groups include, but are not limited to, cyclopentenylene (e.g., 4-cyclopenten-l,3-ylene), cyclohexenylene (e.g., 2-cyclohexen-l,4-ylene; 3-cyclohexen-l,2-ylene; 2,5-cyclohexadien-l,4- ylene).

Ci_-2O alkylene and C₁.₂₀ alkyl groups as defined herein are either uninterrupted or interrupted by one or more heteroatoms or heterogroups, such as S, O or N(R") wherein R" is H, Ci_-6 alkyl or aryl (typically phenyl), or by one or more arylene

(typically phenylene) groups, or by one or more -C(O)- or -C(O)N(R")- groups. The phrase "optionally interrupted" as used herein thus refers to a C_1-20 alkyl group or an alkylene group, as defined above, which is uninterrupted or which is interrupted between adjacent carbon atoms by a heteroatom such as oxygen or sulfur, by a heterogroup such as N(R") wherein R" is H, aryl or Ci-C₆ alkyl, or by an arylene group, or by a -C(O)- or -C(O)N(R")- group, again wherein R" is H, aryl or Ci-C₆ alkyl.

For instance, a Ci_-20 alkyl group such as n-butyl may be interrupted by the heterogroup N(R") as follows: -CH₂N(R")CH₂CH₂CH_3, -CH₂CH₂N(R")CH₂CH₃, or -CH₂CH₂CH₂N(R")CH₃. Similarly, an alkylene group such as n-butylene may be interrupted by the heterogroup N(R") as follows: -CH₂N(R")CH₂CH₂CH₂-, -CH₂CH₂N(R")CH₂CH₂-, or -CH₂CH₂CH₂N(R")CH₂-. Typically an interrupted group, for instance an interrupted C_{I -20} alkylene or Ci_-20 alkyl group, is interrupted by 1, 2 or 3 heteroatoms or heterogroups or by 1, 2 or 3 arylene (typically phenylene) groups. More typically, an interrupted group, for instance an interrupted Ci_-20 alkylene or Ci_-20 alkyl group, is interrupted by 1 or 2 heteroatoms or heterogroups or by 1 or 2 arylene (typically phenylene) groups. For instance, a Ci_-20 alkyl group such as n-butyl may be interrupted by 2 heterogroups N(R") as follows: -CH₂N(R")CH₂N(R")CH₂CH₃. An arylene group is an unsubstituted or substituted bidentate moiety obtained by removing two hydrogen atoms, one from each of two different aromatic ring atoms of an aromatic compound, which moiety has from 5 to 14 ring atoms (unless otherwise specified). Typically, each ring has from 5 to 7 or from 5 to 6 ring atoms. An arylene group may be unsubstituted or substituted, for instance, as specified above for aryl.

In this context, the prefixes (e.g., C_5-20, C_6-20, C_5-14, C_5-7, C_5-6, etc.) denote the number of ring atoms, or range of number of ring atoms, whether carbon atoms or heteroatoms. For example, the term "C_5-6 arylene," as used herein, pertains to an arylene group having 5 or 6 ring atoms. Examples of groups of arylene groups include C_5-20 arylene, C_6-2O arylene, C_5-14 arylene, C_6-14 arylene, C_6-io arylene, C_5-12 arylene, C_5-10 arylene, C_5-7 arylene, C_5-6 arylene, C₅ arylene, and C₆ arylene. The ring atoms may be all carbon atoms, as in "carboarylene groups"

(e.g., C_6-20 carboarylene, C_6-14 carboarylene or C_6-10 carboarylene).

Examples of C_6-20 arylene groups which do not have ring heteroatoms (i.e., C_6-20 carboarylene groups) include, but are not limited to, those derived from the compounds discussed above in regard to aryl groups, e.g. phenylene, and also include those derived from aryl groups which are bonded together, e.g. phenylene- phenylene (diphenylene) and phenylene-phenylene-phenylene (triphenylene).

Alternatively, the ring atoms may include one or more heteroatoms, as in "heteroarylene groups" (e.g., C_5-I0 heteroarylene).

Examples of C_5-I0 heteroarylene groups include, but are not limited to, those derived from the compounds discussed above in regard to heteroaryl groups.

As used herein the term oxo represents a group of formula: =O

As used herein the term acyl represents a group of formula: -C(=O)R, wherein R is an acyl substituent, for example, a substituted or unsubstituted Ci_-20 alkyl group, a substituted or unsubstituted C_3-20 heterocyclyl group, or a substituted or unsubstituted aryl group. Examples of acyl groups include, but are not limited to, -C(=O)CH₃ (acetyl), -C(=O)CH₂CH₃ (propionyl), -C(=O)C(CH₃)₃ (t-butyryl), and -C(=O)Ph (benzoyl, phenone).

As used herein the term acyloxy (or reverse ester) represents a group of formula: -OC(=O)R, wherein R is an acyloxy substituent, for example, substituted or unsubstituted Ci_-20 alkyl group, a substituted or unsubstituted C_3-20heterocyclyl group, or a substituted or unsubstituted aryl group, typically a Ci_-6 alkyl group. Examples of acyloxy groups include, but are not limited to, -OC(=O)CH₃ (acetoxy), -OC(=O)CH₂CH₃, -OC(=O)C(CH₃)₃, -OC(=O)Ph, and -OC(O)CH₂Ph.

As used herein the term ester (or carboxylate, carboxylic acid ester or oxycarbonyl) represents a group of formula: -C(O)OR, wherein R is an ester substituent, for example, a substituted or unsubstituted C_1-20 alkyl group, a substituted or unsubstituted C_3-20 heterocyclyl group, or a substituted or unsubstituted aryl group (typically a phenyl group). Examples of ester groups include, but are not limited to, -C(=O)OCH₃, -C(=O)OCH₂CH₃, -C(=O)OC(CH₃)₃, and -C(O)OPh.

As used herein the term amino represents a group of formula -NH₂. The term Ci-C₁₀ alkylamino represents a group of formula -NHR' wherein R' is a C_1-I0 alkyl group, preferably a C_1-6 alkyl group, as defined previously. The term di(C_1- ]o)alkylamino represents a group of formula -NR'R" wherein R' and R" are the same or different and represent Ci_-I0 alkyl groups, preferably Ci_-6 alkyl groups, as defined previously. The term arylamino represents a group of formula -NHR' wherein R' is an aryl group, preferably a phenyl group, as defined previously. The term diarylamino represents a group of formula -NR'R" wherein R' and R" are the same or different and represent aryl groups, preferably phenyl groups, as defined previously. The term arylalkylamino represents a group of formula -NR'R" wherein R' is a Ci-io alkyl group, preferably a Ci_-6 alkyl group, and R" is an aryl group, preferably a phenyl group.

A halo group is chlorine, fluorine, bromine or iodine (a chloro group, a fluoro group, a bromo group or an iodo group). It is typically chlorine, fluorine or bromine. As used herein the term amido represents a group of formula: -C(O)NR R , wherein R and R are independently amino substituents, as defined for di(Ci. io)alkylamino groups. Examples of amido groups include, but are not limited to, -C(O)NH₂, -C(O)NHCH₃, -C(O)N(CH₃)₂, -C(O)NHCH₂CH₃, and -C(O)N(CH₂CH₃)₂, as well as amido groups in which R and R , together with the nitrogen atom to which they are attached, form a heterocyclic structure as in, for example, piperidinocarbonyl, morpholinocarbonyl, thiomorpholinocarbonyl, and piperazinocarbonyl.

As used herein the term acylamido represents a group of formula: -NR¹C(O)R², wherein R¹ is an amide substituent, for example, hydrogen, a Ci_-2oalkyl group, a C_3-20 heterocyclyl group, an aryl group, preferably hydrogen or a Ci-20 alkyl group, and R² is an acyl substituent, for example, a C_1-20 alkyl group, a C_3-20 heterocyclyl group, or an aryl group, preferably hydrogen or a C_1-20 alkyl group. Examples of acylamide groups include, but are not limited to, -NHC(=O)CH₃ , -NHC(=O)CH₂CH₃, -NHC(O)Ph, -NHC(=0)C I₅H₃₁ and -NHCC=O)C₉H₁₉. Thus, a substituted C_1-20 alkyl group may comprise an acylamido substituent defined by the formula -NHC(=O)-Ci_-20 alkyl, such as -NHCC=O)C₁₅H₃₁ or -NHCC=O)C₉H₁₉. R¹ and R² may together form a cyclic structure, as in, for example, succinimidyl, maleimidyl, and phthalimidyl:

succinimidyl maleimidyl phthalimidyl

A C_1-I0 alkylthio group is a said Ci_-10 alkyl group, preferably a Ci_-6 alkyl group, attached to a thio group. An arylthio group is an aryl group, preferably a phenyl group, attached to a thio group.

A Ci -₂₀ alkoxy group is a said substituted or unsubstituted Ci_-20 alkyl group attached to an oxygen atom. A C_1-6 alkoxy group is a said substituted or unsubstituted C_1-6 alkyl group attached to an oxygen atom. A C_1-4 alkoxy group is a substituted or unsubstituted Ci_-4 alkyl group attached to an oxygen atom. Said Ci_-20, Ci_-6 and Ci_-4 alkyl groups are optionally interrupted as defined herein. Examples OfCi_-4 alkoxy groups include, -OMe (methoxy), -OEt (ethoxy), -O(nPr) (n-propoxy), -O(iPr) (isopropoxy), -O(nBu) (n-butoxy), -O(sBu) (sec-butoxy), -O(iBu) (isobutoxy), and -O(tBu) (tert-butoxy). Further examples Of Ci_-20 alkoxy groups are -O(Adamantyl), - O-CH₂-Adamantyl and -0-CH₂-CH₂- Adamantyl. An aryloxy group is a substituted or unsubstituted aryl group, as defined herein, attached to an oxygen atom. An example of an aryloxy group is -OPh (phenoxy). Unless otherwise specified, included in the above are the well known ionic, salt, solvate, and protected forms of these substituents. For example, a reference to carboxylic acid or carboxyl group (-COOH) also includes the anionic (carboxylate) form (-COO^"), a salt or solvate thereof, as well as conventional protected forms. Similarly, a reference to an amino group includes the protonated form (-N⁺HR¹R²), a salt or solvate of the amino group, for example, a hydrochloride salt, as well as conventional protected forms of an amino group. Similarly, a reference to a hydroxyl group also includes the anionic form (-O^"), a salt or solvate thereof, as well 5 as conventional protected forms.

Certain compounds may exist in one or more particular geometric, optical, enantiomeric, diasteriomeric, epimeric, atropic, stereoisomeric, tautomeric, conformational, or anomeric forms, including but not limited to, cis- and trans-forms; E- and Z-forms; c-, t-, and r- forms; endo- and exo-forms; R-, S-, and meso-forms;

10 D- and L- forms; d- and 1- forms; (+) and (-) forms; keto-, enol-, and enolate-foπns; syn- and anti-forms; synclinal- and anticlinal-forms; a- and /3-forms; axial and equatorial forms; boat-, chair-, twist-, envelope-, and halfchair-forms; and combinations thereof, hereinafter collectively referred to as "isomers" (or "isomeric forms").

15 Note that, except as discussed below for tautomeric forms, specifically excluded from the term "isomers," as used herein, are structural (or constitutional) isomers (i.e., isomers which differ in the connections between atoms rather than merely by the position of atoms in space). For example, a reference to a methoxy group, -OCH₃, is not to be construed as a reference to its structural isomer, a 0 hydroxymethyl group, -CH₂OH. Similarly, a reference to ortho-chlorophenyl is not to be construed as a reference to its structural isomer, meta-chlorophenyl. However, a reference to a class of structures may well include structurally isomeric forms falling within that class (e.g., Ci_-7alkyl includes n-propyl and iso-propyl; butyl includes n-, iso-, sec-, and tert-butyl; methoxyphenyl includes ortho-, meta-, and

25 para-methoxyphenyl).

The above exclusion does not pertain to tautomeric forms, for example, keto, enol, and enolate forms, as in, for example, the following tautomeric pairs: keto/enol (illustrated below), imine/enamine, amide/imino alcohol, amidine/amidine, nitroso/oxime, thioketone/enethiol, N-nitroso/hyroxyazo, and nitro/aci-nitro.

•₃Q keto enol enolate Note that specifically included in the term "isomer" are compounds with one or more isotopic substitutions. For example, H may be in any isotopic form, including ¹H, ²H (D), and ³H (T); C may be in any isotopic form, including ¹²C, ¹³C, and ¹⁴C; O may be in any isotopic form, including ¹⁶O and ¹⁸O; and the like. Unless otherwise specified, a reference to a particular compound includes all such isomeric forms, including (wholly or partially) racemic and other mixtures thereof. Methods for the preparation (e.g., asymmetric synthesis) and separation (e.g., fractional crystallisation and chromatographic means) of such isomeric forms are either known in the art or are readily obtained by adapting known methods, in a known manner.

Unless otherwise specified, a reference to a particular compound also includes ionic, salt, solvated and protected forms.

In the process of the invention for producing for producing a fluorine-labelled compound, the compound of formula (I) is treated with fluoride, [ⁿF]^~, thereby fluorinating and detagging the compound of formula (I) to produce the fluorine- labelled compound of formula (III). This treatment with [ⁿF]^~ is usually carried out in the presence of a solvent. When a solvent is used, any suitable solvent may be employed. Typically, however, the solvent is a polar aprotic solvent, for instance acetonitrile, THF or DMSO. More typically, the solvent is a fluorophilic solvent, for instance acetonitrile.

The fluoro-detagging reaction of step (a) may be carried out at room temperature. More typically, however, the reaction temperature is from 60°C to 160°C, even more typically from 80°C to 160°C. Typically, ⁿF is the fluorine radioisotope ¹⁸F. ¹⁸F-labelled compounds are useful as radiotracers in PET imaging.

Alternatively, however, ⁿF is ¹⁹F, i.e. "cold" fluorine. Compounds containing ¹⁹F are useful as cold "reference" products, e.g. for HPLC characterisation of a corresponding ¹⁸F-radiolabelled compound. ¹⁹F-containing compounds are also useful in magnetic resonance imaging (MRI) applications.

Any suitable source of F^" (¹⁸F^" or ¹⁹F^") may be used. As will be understood by the skilled person the F^" will typically be present in the form of a salt, with a counter cation. Typically, therefore, step (a) of the process of the invention comprises treating the compound of formula (I) with a salt of [ⁿF]^~ in the presence of a solvent.

Any suitable counter cation may be used. Typically, the counter cation is a quaternary ammonium cation, for instance tetrabutylammonium, or an alkali metal cation, for instance Cs⁺ or K⁺, or a proton, H⁺. Typically, when an alkali metal cation is employed, the alkali metal cation complexed in a cryptand, for instance aminopolyether 2.2.2 (K₂₂₂), which is commercially available as Kryptofix-222. Advantageously, the addition of such a cryptand enables the fluoride ion ["F]^" to be solubilized in a polar aprotic solvent, for instance acetonitrile. It also enables the formation of a 'naked fluoride ion' as a KF-K₂₂₂ complex, hi one embodiment, therefore, the source of [ⁿF]^" is a KF-K₂₂₂ complex. The KF-K₂₂₂ complex may be K[¹⁸F]F-K₂₂₂ or K[¹⁹F]F-K₂₂₂, as the case may be. The preparation of a solution of K[¹⁸F]F-K₂₂₂ suitable for fluorination is shown schematically in Fig. 2.

Alternatively, the source of [ⁿF]^~ may be TBAF (tetrabutylammonium fluoride), CsF, or HF.

Typically, when ⁿF is ¹⁸F, the ¹⁸F^" is present as K[¹⁸F]F-K₂₂₂ or [¹⁸F]HF.

More typically, when ⁿF is ¹⁸F, the ¹⁸F^" is present as K[¹⁸F]F-K₂₂₂. Typically, this is heated with the compound of formula (I) in a polar aprotic solvent, such as acetonitrile, for between 10 to 30 minutes at a temperature most often in the range of 60°C to 160°C, more typically 80°C to 160°C.

Typically, when ⁿF is ¹⁹F, the source of ¹⁹F^" is TBAF or CsF.

In the process of the invention for producing a fluorine-labelled compound, the compound of formula (I) which comprises the fluorous tag is detagged in a nucleophilic fluorination reaction to produce a detagged, fluorine-labelled compound of formula (III). Usually, therefore, the reaction mixture comprises the detagged, fluorine-labelled product of formula (III), the solvent, and one or more tagged byproducts which comprise the Rf group of the fluorous tag. Furthermore, as mentioned above, ¹⁸F radiolabelling procedures typically use very large excesses of starting material relative to the ¹⁸F^" source. Typically, therefore, the reaction mixture also comprises an amount of unreacted compound of formula (I) (which of course comprises the fluorous tag, including the fluorous Rf group). Accordingly, in order to purify and/or recover the fluorine-labelled compound of formula (III), that compound usually must be separated from one or more residual fluorous compounds which comprise the group Rf. Typically, therefore, the process of the invention for producing a fluorine-labelled compound comprises: (b) separating the compound of formula (III) from one or more fluorous compounds which comprise Rf. Typically, the one or more residual fluorous compounds comprise unreacted compound of formula (I). Typically, the one or more residual fluorous compounds include one or more by-products which comprise the group Rf. More typically, the one or more residual fluorous compounds include one or more by-products which comprise the group Rf and unreacted compound of formula (I).

The process of the present invention takes advantage of fluorous chemistry to separate the compound of formula (III) from the one or more residual fluorous compounds which comprise Rf, and thereby purify the compound of formula (III). A fluorous tag is a heavily fluorinated extension to a molecule, which often comprises a perfluorinated alkyl chain. These tags allow the reactivity of the compound to mimic that of the analogous organic molecule, and yet be readily separable from one another, as well as other organic species. The use of such tags within organic chemistry can facilitate the separation of compounds with tags from those without, and separation between compounds with fluorous tags of different sizes. Fluorous molecules can be further classed as either being light fluorous or heavy fluorous. These refer to the proportion by weight of fluorine atoms within a molecule. Heavy fluorous molecules typically have at least 39 fluorine atoms, fluorine usually accounting for approximately 60% of the molecular weight. Light fluorous molecules on the other hand have a maximum of, say, 24, 26 or 28 fluorine atoms. In light fluorous molecules, fluorine usually accounts for up to approximately 40% of the molecular weight. A heavy fluorous sugar and the light fluorous mappicine are shown below.

Rf = (C₆Fi₃CH₂CH₂)_SSiC₆H₄CH₂-

Heavy fluorous sugar MW=3838, %F=58 Light fluorous mappicine MW=881, %F=37

Typically, the tagged precursor compound of formula (I) employed in the process of the present invention is a light fluorous compound.

Typically, therefore, the compound of formula (I) contains up to 28, more typically up to 26, or up to 24, fluorine atoms.

In one embodiment, the fluorine atoms present in the tagged precursor compound of formula (I) account for no more than 40% of the molecular weight of the compound of formula (I).

The characteristics of compounds falling in these different classifications (light fluorous and heavy fluorous) lend themselves preferentially to one of two major purification techniques, fluorous solid phase extraction, and fluorous liquid- liquid extraction. Compounds featuring between 21 and 39 fluorine atoms may be applied to both of these techniques, however generally demonstrate less efficient purification. Liquid-Liquid Extraction is largely applied to heavy fluorous molecules and allows the separation of fluorous from organic compounds into two phases, or of fluorous from organic and inorganic compounds into three phases.

Fluorous Solid Phase Extraction (FSPE) uses light fluorous compounds, and involves loading a crude reaction mixture containing organic and light fluorous components onto a column of fluorous silica gel. Fluorous silica has a high affinity for fluorous material. The column is first eluted with a fluorophobic eluent to wash through the organic compounds and leave the fluorous components adsorbed. Further elution with a fluorophilic solvent will then remove the fluorous compounds (Fig 1).

A number of common organic solvents have differing levels of fluorophilic and fluorophobic character, and so the correct elution for specific separations can be determined through trial and error. It is the solubility of light fluorous compounds in these organic solvents with makes them applicable to FSPE (and subsequently makes heavy fluorous compounds inappropriate candidates). FSPE is an easily implemented separation technique, which can be run by automated systems, and doesn't involve the use of fluorous solvents. Furthermore, reactions can be carried out in a homogeneous phase. This allows much more favourable reaction kinetics then solid phase synthesis techniques. Other fluorous separation techniques include fluorous chromatography, used to separate out compounds with different size fluorous tags, fluorous biphasic catalysis, and also fluorous triphasic reactions.

Typically, step (b) of the process of the invention for producing a fluorinated compound comprises separating the compound of formula (III) from said one or more fluorous compounds comprising Rf by Fluorous Solid Phase Extraction

(FSPE). FSPE has the advantage of being a quick and effective purification process; this is especially important in when using radioisotopes PET chemistry, which is strongly influenced by the time constraints involved when using short half life positron emitters such as F. Typically, therefore, step (b) of the process of the invention for producing a fluorinated compound comprises:

(i) loading the reaction mixture onto a fluorous solid phase, and

(ii) selectively eluting the compound of formula (III) from said fluorous solid phase, such that said one or more fluorous compounds comprising Rf are retained on the solid phase.

Typically, the fluorous solid phase is fluorous silica. Typically, step (ii) comprises eluting the compound of formula (III) from said fluorous solid phase using a suitably fluorophobic eluent. In one embodiment, the fluorophobic eluent is a mixture of H₂O and another, less polar solvent, for instance MeCN, acetone, toluene or THF. Usually, the fluorophobic eluent is a mixture of H₂O and MeCN.

Usually, step (b) comprises a further step of (iii) washing the fluorous solid phase with the fluorophobic eluent.

Optionally, after eluting the compound of formula (III), the fluorous compounds comprising Rf are then removed from the solid phase by further elution with a fluorophilic eluent. The fluorophilic eluent is typically neat MeCN. Typically, the process further comprises recovering said compound of formula (III). The compound of formula (III) may be recovered as a solid or as a solution (typically a pure solution) of the compound. hi one embodiment, step (b) of the process of the invention for producing a fluorinated compound comprises:

(i) loading the reaction mixture onto a fluorous solid phase, and (ii) selectively eluting the compound of formula (III) from said fluorous solid phase, using a suitably fluorophobic eluent, such that said one or more fluorous compounds comprising Rf are retained on the solid phase, and

(iii) recovering the compound of formula (III) as a solution of said compound in said fluorophobic eluent.

The fluorous tag in the compounds of formula (I) is a group of formula (II) as defined above. Typically, in the group of formula (II), L is a single bond or an unsubstituted Ci_-10 alkylene group. More typically, L is a single bond or an unsubstituted Ci_-6 alkylene group. Even more typically, L is unsubstituted Ci_-6 alkylene, for instance methylene, ethylene, propylene or butylene. In one embodiment, L is ethylene.

Rf, in the group of formula (II), is any C_4-I2 perfluoro alkyl group. Thus Rf is typically selected from perfluorobutyl (C₄) (including perfluoro-«-butyl, perfluoro- sec-butyl and perfluoro-tert-butyl), perfluoropentyl (C₅), perfluorohexyl (C₆), perfluoroheptyl (C₇), perfluorooctyl (C₈), perfluorononyl (Cg), perfluorodecyl (Ci₀), perfluoroundecyl (Cn) or perfluorododecyl (Cj₂), including the straight chained and branched isomers thereof. Usually, Rf is -(CF₂)₅CF₃, -(CF₂)₆CF₃ or -(CF₂)₇CF₃. More typically, Rf is -(CF₂)₅CF₃ or -(CF₂)₇CF₃. In one embodiment, Rf is - (CF₂)₇CF₃.

In one embodiment, L is methylene, ethylene or propylene and Rf is - (CF₂)₅CF₃, -(CF₂)₆CF₃ or -(CF₂)₇CF₃.

In the compounds of formula (I), R¹, R² and the C(H) group to which R¹ and R² are bonded together form a moiety to be labelled with fluorine. Thus, R¹, R² and said C(H) group can be any moiety, typically any organic moiety, which is desired to be labelled. In that moiety, R¹ and R² may be separate unconnected groups. Alternatively, R¹ and R² and the C(H) group to which R¹ and R² are bonded may together form a ring system, for instance an aryl, heteroaryl, C_3-25 cycloalkyl or C_3-20 hererocyclyl ring system.

Typically, R² is H and R¹ is a group of formula (VI)

wherein L' is a single bond or -alk-, wherein -alk- is as defined above, and R³ is H, unsubstituted or substituted Ci_-6 alkyl, aryl or an amine protecting group; or R² is H and R¹ is a group of formula (VII)

wherein L' is a single bond or -alk-, wherein -alk- is as defined above; or R² is H and R¹ is a group of formula (VIII)

wherein L' is a single bond or -alk-, wherein -alk- is as defined above, and X² is a halo group; or

R² is H and R¹ is a group of formula (IX)

(IX) wherein L' is a single bond or -alk-, wherein -alk- is as defined above, R⁴ is unsubstituted or substituted C_1-6 alkyl, aryl or an amine protecting group and R⁵ is unsubstituted or substituted C_1-6 alkyl, aryl, acyl or a carboxyl protecting group; or R² is H and R¹ is a group of formula (X)

R° (X) wherein L' is a single bond or -alk-, wherein -alk- is as defined above, and R⁶ is H, unsubstituted or substituted Ci_-6 alkyl, aryl or an amine protecting group; or R² is H and R¹ is a group of formula (XI)

wherein L' is a single bond or -alk-, wherein -alk- is as defined above, and R⁷ and R⁸ are independently selected from H, unsubstituted or substituted Ci_-6 alkyl, aryl or an amine protecting group; or

R² is H and R¹ is a group of formula (XII)

wherein L' is a single bond or -alk-, wherein -alk- is as defined above, R is unsubstituted or substituted Ci_-6 alkyl, aryl or an amine protecting group and R¹ is is unsubstituted or substituted Ci_-6 alkyl, aryl, acyl or a hydroxyl protecting group; or R¹, R² and the C(H) group to which R¹ and R² are both bonded together form a group of formula (XIII)

wherein R¹¹ is unsubstituted or substituted Ci_-6 alkyl, aryl, acyl or a hydroxyl protecting group and R¹² is unsubstituted or substituted Ci_-6 alkyl, aryl or an amine protecting group; or

R¹, R² and the C(H) group to which R¹ and R² are both bonded together form a group of formula (XIV)

R¹, R² and the C(H) group to which R¹ and R² are both bonded together form a group of formula (XV)

wherein R¹³, R¹⁴, R¹⁵ and R¹⁶ are the same or different and are independently selected from acyl, unsubstituted or substituted Ci_-6 alkyl, aryl, or a hydroxyl protecting group; or

R¹, R² and the C(H) group to which R¹ and R² are both bonded together form a group of formula (XVI)

wherein R¹⁷, R¹⁸ and R¹⁹ are the same or different and are independently selected from acyl, unsubstituted or substituted C_1-6 alkyl, aryl, or a hydroxyl protecting group; or

R¹, R² and the C(H) group to which R¹ and R² are both bonded together form a group of formula (XVII)

wherein R²⁰ is H, unsubstituted or substituted Ci_-6 alkyl, aryl, acyl or a hydroxyl protecting group and R²¹ is H, unsubstituted or substituted Ci_-6 alkyl, aryl or an amine protecting group; or

R¹, R² and the C(H) group to which R¹ and R² are both bonded together form a group of formula (XVIII)

(XVIII) wherein R²² is an amine protecting group; or R² is H and R¹ is -alk-N₃, wherein -alk- is as defined above; or

R² is H and R¹ is -alk-C ≡€H, wherein -alk- is as defined above; or R² is H and R¹ is -alk-CH=CH₂, wherein -alk- is as defined above; or R² is H and R¹ is -alk-R²³, wherein -alk- is as defined above and R²³ is substituted or unsubstituted aryl; or R² is H and R¹ is a group of formula (XIX)

wherein L² is -alk-, wherein -alk- is as defined above and z is 0 or 1 ; or R² is H and R¹ is a group of formula (XX)

wherein L³ is -alk- or -alk-arylene-, wherein -alk- is as defined above and z is

0 or 1 ; or

R² is H and R¹ is a group of formula (XXI)

wherein L⁴ is -alk- or -alk-arylene-, wherein -alk- is as defined above and z is O or l; or

R² is H and R¹ is a group of formula (XXIV)

>— u 5 O — ( second fluorous tag)

(XXIV)

wherein L⁵ is -alk-, wherein -alk- is as defined above, and wherein the second fluorous tag is a group of formula (XXV)

wherein Rf²"⁰ is a straight-chained or branched C_4-I2 perfiuoroalkyl group, provided that the total number of carbon atoms in Rf and Rf^nd together does not exceed 12, and L^2nd is a single bond, -alk-, -arylene-, -alk-arylene-, alk-X-, -arylene-X-, -alk- arylene-X, -alk-X-arylene-, -alk-X-arylene-X-, -arylene-alk-, -arylene-X-alk-, -arylene-alk-X- or -arylene-X-alk-X-, wherein X is N(R"), O, S, C(O) or C(O)N(R") and wherein alk is as defined above. Typically, Rf^nd, in the group of formula (XXV), is selected from perfluorobutyl (C₄) (including perfluoro-«-butyl, perfluoro-sec-butyl and perfluoro- tert-butyl), perfluoropentyl (C₅), and perfluorohexyl (C₆), perfluoroheptyl (C₇), and perfluorooctyl (C₈), including the straight chained and branched isomers thereof. Usually, Rf²"" is -(CF₂)₅CF₃, -(CF₂)₆CF₃ or -(CF₂)₇CF₃. More typically, Rf²"" is - (CF₂)₅CF₃. In one embodiment, Rf and R?^πd are both -(CF₂)₅CF₃.

Typically, L^2nd is methylene, ethylene or propylene. More typically, L^2nd is ethylene. In one embodiment, L and L^2nd are both ethylene.

Typically R¹, R² and the C(H) group to which R¹ and R² are bonded together form (i) a tracer moiety, (ii) a moiety which is a precursor to a tracer moiety, or (iii) a labelling agent moiety, which labelling agent moiety comprises a functional group suitable for attaching the compound of formula (III) to a tracer moiety or to a precursor of a tracer moiety. hi one embodiment, R¹, R² and the C(H) group to which R¹ and R² are bonded together form a tracer moiety. The term "tracer moiety", as used herein, means a moiety which has an affinity for a biological target or any moiety which, when labelled, enables the imaging and quantification of a biochemical process or of a specific low density protein target in vivo.

Tracer moieties therefore include biologically active molecules such as peptides (including oligopeptides, polypeptides and proteins) and amino acids. Examples of compounds of formula (I) in which R¹, R² and the C(H) group to which R¹ and R² are bonded together form a tracer moiety are as follows:

(1) Compounds of formula (I) in which R² is H and R¹ is a group of formula (VIII) as defined above. Such compounds can be used to synthesise the well-known ¹⁸F tracers [¹⁸F]FECNT and [¹⁸F]Fp- CIT, and structurally similar compounds.

(2) Compounds of formula (I) in which R² is H and R¹ is a group of formula (VII) as defined above. Such compounds can be used to synthesise the well-known ¹⁸F tracer [¹⁸F]FBR and structurally similar compounds.

(3) Compounds of formula (I) in which R¹, R² and the C(H) group to which R¹ and R² are bonded together form a group of formula (XrV) as defined above. Such compounds can be used to sysnthesise the well-known ¹⁸F tracer [¹⁸F]FCWAY.

Typically, therefore, in the process of the invention for producing a fluorine- labelled compound, ⁿF is ¹⁸F, R² is H and R¹ is a group of formula (VIII)

wherein L' is CH₂, X² is either Cl or I and the fluorine-labelled compound of formula (III) is either

[ rl¹8⁸F]FECNT or

In another embodiment of the process of the invention for producing a fluorine-labelled compound, ⁿF is ¹⁸F, R² is H and R¹ is a group of formula (VII)

wherein L' is a single bond and the fluorine-labelled compound of formula (III) is

In another embodiment of the process of the invention for producing a fluorine-labelled compound, "F is ¹⁸F, and R¹, R² and the C(H) group to which R¹ and R² are both bonded together form a group of formula (XIV)

wherein the fluorine-labelled compound of formula (III) is

[¹⁸F]FCWAY.

Some radiotracers cannot withstand the harsh reaction conditions required for efficient and late [¹⁸F] -labelling in high radiochemical yields. In such cases, a protected precursor of the molecule can be labelled and the fluorine-labelled precursor subsequently deprotected.

Accordingly, in another embodiment, R¹, R² and the C(H) group to which R¹ and R² are bonded together form a moiety which is a precursor to a tracer moiety. The term "a moiety which is a precursor to a tracer moiety", as used herein, means any moiety which can be readily converted into a tracer moiety. Typically, the precursor is a protected version of the tracer moiety which can be converted into the tracer moiety by deprotection of the precursor after fluorination. Typically, therefore the term "a moiety which is a precursor to a tracer moiety" means any precursor moiety which can be readily converted into the corresponding tracer moiety by deprotecting one or more functional groups in the precursor.

Examples of compounds of formula (I) in which R¹, R² and the C(H) group to which R and R² are bonded together form a moiety which is a precursor to a tracer moiety are as follows:

(A) Compounds of formula (I) in which R¹, R² and the C(H) group to which R¹ and R² are bonded together form a group of any one of formulae (XV), (XIII), (XVII) and (XVIII) as defined above. Such compounds can be used to synthesise the well-known ¹⁸F tracers [¹⁸F]FDG, [¹⁸F]FLT, [¹⁸F]cw-fluoroproline, and structurally similar compounds, by nucleophilic fluorination in accordance with the process of the present invention, followed by deprotection of the resulting fluorine-labelled compound.

(B) Compounds of formula (I) in which R² is H and R¹ is a group of any one of formulae (VI), (IX), (X) and (XI) as defined above. Such compounds can be used to synthesise the well-known ¹⁸F tracers [¹⁸F]Fallypride, [¹⁸F]SPA-RQ, [¹⁸F]FET and [¹⁸F]FMeNER-^ and structurally similar compounds, by nucleophilic fluorination in accordance with the process of the present invention, followed by deprotection of the resulting fluorine-labelled compound.

Accordingly, in one embodiment of the process of the invention, R¹, R² and the C(H) group to which R¹ and R² are bonded together form a moiety which is a precursor to a tracer moiety, and the process further comprises:

(c) converting said moiety which is a precursor into said tracer moiety, thereby producing a further compound of formula (III) which comprises a tracer moiety.

Typically, in this embodiment:

• R¹, R² and the C(H) group to which R¹ and R² are both bonded together form a group of formula (XV)

wherein R¹³, R¹⁴, R¹⁵ and R¹⁶ are the same or different and are independently selected from acyl, unsubstituted or substituted C_1-6 alkyl, aryl, or a hydroxyl protecting group, and the process comprises:

(c) deprotecting the fluorine-labelled compound of formula (III) and thereby producing said further compound of formula (III) which is a compound of formula (XXXXXI)

(XXXXXI); or

• R² is H and R¹ is a group of formula (VI)

wherein L' is a single bond or -alk-, wherein -alk- is as defined in claim 1, and R³ is H, unsubstituted or substituted Ci_-6 alkyl, aryl or an amine protecting group, and the process comprises:

(c) deprotecting the fluorine-labelled compound of formula (III) and thereby producing said further compound of formula (III) which is a compound of formula (XXXXVII)

(XXXXVII); or

R² is H and R¹ is a group of formula (IX)

wherein L' is a single bond or -alk-, wherein -alk- is as defined in claim 1, R⁴ is unsubstituted or substituted Ci_-6 alkyl, aryl or an amine protecting group and R⁵ is unsubstituted or substituted Ci_-6 alkyl, aryl, acyl or a carboxyl protecting group, and the process comprises:

(c) deprotecting the fluorine-labelled compound of formula (III) and thereby producing said further compound of formula (III) which is a compound of formula (XXXXVIII)

H₅N (XXXXVIII); or

R² is H and R¹ is a group of formula (X)

wherein L' is a single bond or -alk-, wherein -alk- is as defined in claim 1, and R⁶ is H, unsubstituted or substituted Ci_-6 alkyl, aryl or an amine protecting group, and the process comprises:

(c) deprotecting the fluorine-labelled compound of formula (III) and thereby producing said further compound of formula (III) which is a compound of formula

(XXXXIX)

(XXXXIX); or R² is H and R¹ is a group of formula (XI)

wherein L' is a single bond or -alk-, wherein -alk- is as defined in claim 1, and R⁷ and R⁸ are independently selected from H, unsubstituted or substituted C_1-6 alkyl, aryl or an amine protecting group, and the process comprises:

(c) deprotecting the fluorine-labelled compound of formula (III) and thereby producing said further compound of formula (III) which is a compound of formula (XXXXX)

(XXXXX); or

R¹, R² and the C(H) group to which R¹ and R² are both bonded together form a group of formula (XIII)

wherein R¹¹ is unsubstituted or substituted Ci_-6 alkyl, aryl, acyl or a hydroxyl protecting group and R¹² is unsubstituted or substituted Ci_-6 alkyl, aryl or an amine protecting group, and the process comprises: (c) deprotecting the fluorine-labelled compound of formula (III) and thereby producing said further compound of formula (III) which is a compound of formula (XXXXXI)

nF (XXXXXI); or

wherein R²⁰ is H, unsubstituted or substituted C_1-6 alkyl, aryl, acyl or a hydroxyl protecting group and R²¹ is H, unsubstituted or substituted C_1-6 alkyl, aryl or an amine protecting group, and the process comprises:

(XXXXXII)

(XXXXXII); or

(XVIII) wherein R²² is an amine protecting group, and the process comprises: (c) deprotecting the fluorine-labelled compound of formula (III) and thereby producing said further compound of formula (III) which is a compound of formula

(XXXXXII)

(XXXXXII).

More typically, in this embodiment, ⁿF is ¹⁸F and the further compound of formula (III) is any one of the following compounds:

[¹⁸F]FDG, [ rl8 F]αs-fluoroproline,

[ _r1¹8⁸F]Fallypride,

[¹⁸F]FLT, [ rl¹8⁸F]SPA-RQ,

Thus, in one embodiment, when R² is H and R¹ is a group of formula (X) as defined above, R² and the hydrogen atom of the C(H) group to which R¹ and R² are both bonded are both ²H, i.e. deuterium. Thus, compounds such as [¹⁸F]FMeNER-J₂ and structurally similar compounds can be produced by the process of the invention. Suitable amine (NH) protecting groups are well known to the skilled person, and include, but are not limited to, t-Butyl carbamate (Boc), 9-fluorenylmethyl carbamate (Fmoc), benzyl carbamate, acyl groups, trityl, tosyl and benzyl.

Typically, the amine protecting group is t-Butyl carbamate (Boc). Other amine protecting groups include alkyl and aryl groups. Suitable reaction conditions for deprotection are well known to the skilled person, and include nucleophilic substitution and and catalytic hydrogenation. Suitable hydroxyl (OH) protecting groups are well known to the skilled person, and include, but are not limited to, acyl groups (for instance, acetyl, benzoyl) and substituted or unsubstituted alkyl, alkenyl or alkaryl groups, for instance methoxymethyl (MOM), tetrahydropyranyl (THP), tert-butyl, benzyl, allyl, and tert- butyldimethylsilyl (TBDMS). Suitable reaction conditions for deprotection are well known to the skilled person, and include hydrogenolysis and acid hydrolysis.

Suitable carboxyl (COOH) protecting groups are well known to the skilled person, and include, but are not limited to, unsubstituted or substituted Ci_-6 alkyl (for instance methyl and ethyl) and alkaryl (for instance benzyl); these protecting groups form simple esters to protect the carboxyl group. Suitable reaction conditions for deprotection are well known to the skilled person, and include ester hydrolysis (saponification) and catalytic hydrogenation.

Some radiotracers cannot withstand the harsh reaction conditions required for efficient and late [¹⁸F] -labelling in high radiochemical yields. In such cases, the molecule can be labelled through coupling with a small labelled prosthetic group via a much milder reaction.

Accordingly, in one embodiment, R¹, R² and the C(H) group to which R¹ and R² are bonded together form a labelling agent moiety, which labelling agent moiety is a moiety that comprises a functional group suitable for attaching the fluorine- labelled compound of formula (III) to a tracer moiety or to a precursor of a tracer moiety.

Examples of compounds of formula (I) in which R¹, R² and the C(H) group to which R¹ and R² are bonded together form a labelling agent moiety are as follows: Compounds of formula (I) in which R² is H and R¹ is:

(A) a group of formula (XIX) as defined above (can be derivatised via the nucleophilic attack of an amine);

(B) -alk-N₃ (can be derivatised via the click reaction);

(C) a group of formula (XX) as defined above (reacts with hydrazine to form a terminal NH₂ functional group, for further reaction);

(D) -alk-C ≡CH (can be derivatised via the click reaction);

(E) -alk-CH=CH₂;

(F) a group of formula (XXIV) as defined above (reacts with -OH, -NH and - COOH functionalities); and (G) a group of formula (XXI) as defined above (reacts with -SH); and

(H) Compounds of formula (I) in which R¹, R² and the C(H) group to which R¹ and R² are bonded together form a group of formula (XVI) as defined above (can be derivatised via the click reaction).

Accordingly, in one embodiment of the process of the invention for producing a fluorine-labelled compound, R¹, R² and the C(H) group to which R¹ and R² are bonded together form said labelling agent moiety which comprises a functional group, and the process further comprises: (c) attaching to the compound of formula (III) a tracer moiety or a moiety which is a precursor of a tracer moiety, thereby producing a further compound of formula (III) which comprises a tracer moiety or a moiety which is a precursor of a tracer moiety.

Typically, in embodiments wherein step (c) comprises attaching to the compound of formula (III) a moiety which is a precursor of a tracer moiety, the further comprises: (d) converting said moiety which is a precursor into said tracer moiety, thereby producing a further compound of formula (III) which comprises a tracer moiety. hi one embodiment, R² is H and R¹ is a group of formula (XIX)

wherein L² is -alk-, wherein -alk- is as defined above and z is 0 or 1 ; and the process comprises:

(c) treating the fluorine-labelled compound of formula (III) with an amine of formula (XXVI)

R²⁶ (XXVI) wherein either (i) R²⁵ and R²⁶ and the NH group to which R²⁵ and R²⁶ are bonded together form an unsubstituted or substituted C_3-7 heterocyclyl group, or (ii) R²⁶ is hydrogen and R²⁵ is unsubstituted or substituted Ci_-20 alkyl, aryl, -alk- Ar, a tracer moiety or a precursor of a tracer moiety, wherein alk is as defined above and Ar is aryl; and thereby producing a compound of formula (XXVII)

(XXVII).

Typically, the reaction is carried out in the presence of a solvent, and more typically in the presence of heat and a solvent. The solvent may be any suitable solvent and is typically a polar aprotic solvent, for instance acetonitrile.

Typically, in this embodiment, ⁿF is ¹⁸F, z is 0, the amine of formula (XXVI) is:

and the compound of formula (XXVII) produced is:

r [l¹8⁸τF]FMISO.

Alternatively, in this embodiment, ⁿF is ¹⁸F, z is O, the amine of formula (XXVI) is:

and the compound of formula (XXVII) produced is:

In another embodiment, R is H and R is -alk-N₃, wherein alk is as defined above, and the process further comprises: (c) treating the fluorine-labelled compound of formula (III) with an alkyne of formula (XXVIII)

HC ≡€-R²⁷ (XXVIII)

wherein R²⁷ is -alk-N(R")-C(O)-R²⁸, -alk-R²⁹, -alk-C(O)-R²⁹, -C(O)-R²⁹, a tracer moiety, or a moiety which is a precursor to a tracer moiety, wherein alk is as defined above, R" is H, C_1-6 alkyl or aryl, R is unsubstituted or substituted Ci_-20 alkyl or aryl, and R²⁹ is a group which comprises a peptide or amino acid residue, and thereby producing a compound of formula (XXIX)

(XXIX).

In one embodiment, the alkyne of formula (XXVIII) is:

and the compound of formula (XXIX) produced is:

The click reaction between an azide and an alkene is typically carried out in the presence of a Cu(I) catalyst. Usually, the Cu(I) catalyst is generated in situ through the reduction of Cu(II), typically in the form of CuSO₄. The reduction is usually carried out by sodium ascorbate. Thus the click reaction is typically performed in the presence of CuSO₄ and sodium ascorbate. Typically, the reaction is carried out in the presence of a solvent, and may be carried out in the presence or absence of heat. The solvent may be any suitable solvent and is typically a polar aprotic solvent, for instance acetonitrile, THF or DMF.

In one embodiment, R¹, R² and the C(H) group to which R¹ and R² are both bonded together form a group of formula (XVI)

wherein R¹⁷, R¹⁸ and R¹⁹ are the same or different and are independently selected from acyl, unsubstituted or substituted Ci_-6 alkyl, aryl, or a hydroxyl protecting group, and the process comprises:

(c) treating the fluorine-labelled compound of formula (III) with an alkyne of formula (XXVIII) HC ≡C-R²⁷ (XXVIII)

wherein R²⁷ is -alk-N(R")-C(O)-R²⁸, -alk-R²⁹, -alk-C(O)-R²⁹, -C(O)-R²⁹, a tracer moiety, or a moiety which is a precursor to a tracer moiety, wherein alk is as defined above, R" is H, Ci_-6 alkyl or aryl, R²⁸ is unsubstituted or substituted Cj_-20 alkyl or aryl, and R²⁹ is a group which comprises peptide or amino acid residue, and thereby producing a compound of formula (XXX)

The preceding reaction is also a click reaction, between an azide and a terminal alkyne, and is typically carried out in the presence of a Cu(I) catalyst, as described above. hi one embodiment, R² is H and R¹ is -alk-N₃, wherein alk is as defined above, and the process comprises: (c) treating the fluorine-labelled compound of formula (III) with a compound of formula (XXXI)

wherein R³⁰ is Ci_-6 alkyl or aryl, L⁸ and L⁹, which are the same or different, are -alk-, wherein alk is as defined above, z is 0 or 1, and R³¹ is a group which comprises a peptide or amino acid residue, a tracer moiety, or a moiety which is a precursor to a tracer moiety, and thereby producing a compound of formula (XXXII)

(XXXII).

The preceding reaction is a Staudinger Ligation of a phosphinothioester and an azide. Such ligations are described in Nilsson et al., Organic Letters, 2001, Vol. 3, No. 1, 9-12. Typically the reaction is carried out in the presence of a solvent. It may be carried out in the presence or absence of heat. Any suitable solvent may be used. Typically, however, the solvent is a polar aprotic solvent, for instance THF or acetonitrile. The solvent may be a mixture of water and a polar aprotic solvent (for instance THF or acetonitrile). In one embodiment, R¹, R² and the C(H) group to which R¹ and R² are both bonded together form a group of formula (XVI)

wherein R¹⁷, R¹⁸ and R¹⁹ are the same or different and are independently selected from acyl, unsubstituted or substituted Cj_-6 alkyl, aryl, or a hydroxyl protecting group, and the process further comprises:

(c) treating the fluorine-labelled compound of formula (III) with a compound of formula (XXXI)

wherein R³⁰ is Ci_-6 alkyl or aryl, L⁸ and L⁹, which are the same or different, are -alk-, wherein alk is as defined above, z is 0 or 1, and R³¹ is a group which comprises a peptide or amino acid residue, a tracer moiety, or a moiety which is a precursor to a tracer moiety, and thereby producing a compound of formula (XXXIII)

(XXXIII).

The preceding reaction is a Staudinger Ligation and is typically carried out in the presence of a solvent, as detailed above. It may be carried out in the presence or absence of heat.

In one embodiment, R² is H and R¹ is a group of formula (XX)

wherein L³ is -alk- or -alk-aryiene-, wherein -alk- is as defined above and z is 0 or 1, and the process comprises:

(c) treating the fluorine-labelled compound of formula (III) with hydrazine, and thereby producing a compound of formula (XXXIV)

(XXXIV).

Typically, the preceding reaction is carried out in the presence of a solvent. It may be carried out in the presence or absence of heat. Any suitable solvent may be used. Typically, however, the solvent is a polar aprotic solvent, for instance THF or acetonitrile, or a mixture of water and a polar aprotic solvent, for instance water and acetonitrile.

Typically, in this embodiment, the process further comprises: (d) treating the compound of formula (XXXIV) thus produced with an ester of formula (XXXV)

wherein R³³ is unsubstituted or substituted C_3-7 heterocyclyl, a group which comprises a peptide or amino acid residue, a tracer moiety, or a moiety which is a precursor to a tracer moiety, L¹⁰ is -alk-, wherein alk is as defined above, a is 0 or 1, and R³² is unsubstituted or substituted Ci_-I0 alkyl or unsubstituted or substituted aryl, and thereby producing a compound of formula (XXXVI)

(XXXVI).

Typically, in this embodiment, ⁿF is ¹⁸F, a is 1, L¹⁰ is a methylene group, z is 1, L³ is a methylene group, R³³ is

and the compound of formula is

hi another embodiment, R² is H and R¹ is -alk-C ^H, wherein -alk- is as defined above, and the process further comprises:

(c) treating the fluorine-labelled compound of formula (III) with an azide of formula (XXXVII)

N₃-R³⁴ (XXXVII)

wherein R³⁴ is -alk-R³⁵, -alk-C(O)-R³⁵, -C(O)-R³⁵, a tracer moiety, or a moiety which is a precursor to a tracer moiety, wherein alk is as defined above and R³⁵ is unsubstituted or substituted C_1-20 alkyl, aryl, or a group which comprises a peptide or an amino acid residue, and thereby producing a compound of formula (XXXVIII)

(XXXVIII).

The preceding reaction is a click reaction, between an azide and a terminal alkyne, and is typically carried out in the presence of a Cu(I) catalyst, as described above. In one embodiment, R² is H and R¹ is a group of formula (XXIV) I — L⁵— O — C second fluorous tag) rχχτ\Λ

wherein Rf²"⁰ is a straight-chained or branched C_4-I2 perfluoroalkyl group, provided that the total number of carbon atoms in Rf and Rf^2nd together does not exceed 12, and L^2nd is a single bond, -alk-, -arylene-, -alk-arylene-, alk-X-, -arylene-X-, -alk- arylene-X, -alk-X-arylene-, -alk-X-arylene-X-, -arylene-alk-, -arylene-X-alk-, -arylene-alk-X- or -arylene-X-alk-X-, wherein X is N(R"), O, S, C(O) or C(O)N(R") and wherein alk is as defined above, and the process comprises:

(c) treating the fluorine-labelled compound of formula (III) with a compound of formula (XXXIX)

(XXXIX) wherein X² is a halo group, and thereby producing a compound of formula

(XXXX)

Typically, in this embodiment, "F is ¹⁸F, L⁵ is CH₂, X² is either Cl or I and the compound of formula (XXXX) produced is either

[¹⁸F]FECNT or

In another embodiment, R^z is H and R' is a group of formula (XXIV)

3 — L⁵ — O — ( second fluorous tag)

(XXIV)

wherein Rf²"*¹ is a straight-chained or branched C_4-I2 perfluoroalkyl group, provided that the total number of carbon atoms in Rf and Rf²¹"¹ together does not exceed 12, and

L^2πd is a single bond, -alk-, -arylene-, -alk-arylene-, alk-X-, -arylene-X-, -alk- arylene-X, -alk-X-arylene-, -alk-X-arylene-X-, -arylene-alk-, -arylene-X-alk-,

-arylene-alk-X- or -arylene-X-alk-X-, wherein X is N(R"), O, S, C(O) or C(O)N(R") and wherein alk is as defined above, and the process comprises:

(c) treating the fluorine-labelled compound of formula (III) with a compound of formula (XXII)

wherein R²³ is NO₂, a tracer moiety, a group which is a precursor to a tracer moiety, a group which comprises a peptide or a group which comprises an amino acid residue, and thereby producing a compound of formula (XXIII)

(XXIII); or

(c) treating the fluorine-labelled compound of formula (III) with a compound of formula (XXXXI)

(XXXXI) wherein R²⁴ is NO₂, a tracer moiety, a group which is a precursor to a tracer moiety, a group which comprises a peptide or a group which comprises an amino acid residue, and thereby producing a compound of formula (XXXXII)

(XXXXII); or

(c) treating the fluorine-labelled compound of formula (III) with a compound of formula (XXXXIII)

(XXXXIII) wherein R³⁶ is unsubstituted or substituted C_3-7 heterocyclyl, a tracer moiety, a group which is a precursor to a tracer moiety, a group which comprises a peptide or a group which comprises an amino acid residue, and L¹¹ is a single bond or -alk-, wherein alk is as defined above, and thereby producing a compound of formula (XXXXIV)

(XXXXIV).

In another embodiment, R² is H and R¹ is a group of formula (XXI)

wherein L⁴ is -alk- or -alk-arylene-, wherein -alk- is as defined above and z is

0 or 1, and the process comprises:

(c) treating the fluorine-labelled compound of formula (III) with a thiol of formula (XXXXV)

HS-L¹²-R³⁷ (XXXXV)

wherein L¹² is a single bond, -alk- or arylene and R³⁷ is a tracer moiety, a group which is a precursor to a tracer moiety, a group which comprises a peptide or a group which comprises an amino acid residue, and thereby producing a compound of formula (XXXXVI)

(XXXXVI).

In the compounds of formula (I) of the present invention, the groups R¹, R , L and Rf are as defined hereinbefore. hi one embodiment, the compound of formula (I) of the present invention is selected from any one of the following compounds:

and

In the process of the invention for producing a compound of formula (I), as defined above, or in the combination product of the invention as defined above, the R¹ and R² groups in the compound of formula (FV) are as defined herein for the corresponding compounds of formula (I). Similarly, the Rf and L groups in the tag compound of formula (V) are as defined herein for the corresponding compounds of formula (I). hi one embodiment, the compound of formula (IV) is any one of the following compounds:

Typically, the compound of formula (V) is one of the following compounds:

The process of the invention for producing a compound of formula (I), as defined above, comprises treating an alcohol of formula (IV) with a compound of formula (V). Typically, the reaction is carried out in the presence of a solvent. Any suitable solvent can be used. Typically, however, the solvent is a polar aprotic solvent, for instance dichloromethane. The reaction can be carried out in the presence or absence of heat. Typically, the reaction is carried out in the presence of a base. The base is typically a trialkylamine, for instance triethylamine. In one embodiment of the process of the invention for producing a compound of formula (I), R² is H and R¹ is -alk-C ^H, wherein -alk- is as defined above, and the process further comprises treating the compound of formula (I) thus produced with an azide of formula (XXXVII) N₃-R³⁴ (XXXVII) wherein R³⁴ is -alk-R³⁵, -alk-C(O)-R³⁵, -C(O)-R³⁵, a tracer moiety, or a moiety which is a precursor to a tracer moiety, wherein alk is as defined above and R³⁵ is unsubstituted or substituted Ci_-20 alkyl, aryl, or a group which comprises a peptide or an amino acid residue, and thereby producing a further compound of formula (I) having the following formula:

The preceding reaction is a click reaction, between an azide and a terminal alkyne, and is typically carried out in the presence of a Cu(I) catalyst, as described above.

The present invention will be further illustrated in the Examples which follow:

EXAMPLES

Formation of Fluorous Tags

Fluorous tags were synthesized in a two step procedure as outlined below (Scheme 1) Thiourea, EtOH

Rf' 9h, 78⁰C, Reflux ι

R_f = C₈F₁₇ Or C_nF (3) R_f = C₈F₁₇ 96% (4) R_f = C

'6^ 13 8^F 17 86% (S) R_f= C₆F₁₃ >99% (6) Rf = c ₆F l3 87%

Scheme 1 - Synthesis of Second Generation Fluorous Tag

lH,lH,2H,2H-perfluorodecyl thiouronium iodide (3) was produced in 96% yield by refluxing lH,lH,2H,2H-perfluorodecyl iodide with thiourea. The subsequent simultaneous oxidation and chlorination using acetic acid, water, and chlorine gas (generated from KMnO₄ and HCl), delivered lH,lH,2H,2H-perfluorodecane sulfonyl chloride (4) in 86% yield. The same reaction sequence was performed with a slightly lighter fluorous group, whereby R_f = C₆Fi₃. This produced 1H,1H,2H,2H- perfluorooctyl thiouronium iodide (5) in quantitative yield, and the corresponding lH,lH,2H,2H-perfluorooctane sulfonyl chloride (6) in 87% yield. The second generation C₈Fn fluorous sulfonyl chloride was reacted with 4-phenyl butan-1-ol, resulting in the production of 4-phenyl-butyl-lH,lH,2H,2H-perfluorodecane-l- sulfonate (7) in a yield of 78%. After nucleophilic fluorination with TBAF, the subsequent l-fluoro-4-phenyl butane product was formed in 3% yield (Scheme 2). This fiuorinated product also gave a characteristic peak in the ¹⁹F NMR at -218.4 ppm.

(7) 78% (2) 3%

Scheme 2 - Confirmation of Nucleophilic Fluoro-Detagging Methodology

Fluorous Tagging of Selected Alcohols Synthesis of Alcohols

Following the successful production of lH,lH,2H,2H-perfluorodecane sulfonyl chloride, a range of alcohols were synthesized for subsequent tagging. The alcohols were chosen either as precursors to known radiotracers, or to demonstrate the versatility of the tagging fluoro-detagging protocol. For each precursor we had the subsequent aim of implementing FSPE purification to separate the pure fluorinated product from the fluorous precursor which is typically used in large excess. The alcohols chosen to synthesize were either not commercially available, or not practical to purchase.

2-Azido-l-ethanol was synthesized via substitution of bromide with sodium azide on 2-bromoethanol under reflux. The resulting 2-azido-l-ethanol (8) product was stored in DCM and used in the tagging process without purification or isolation due to its volatile and explosive nature (Scheme 3).

Reflux 100⁰C, 16h ^

Scheme 3 - Synthesis of 2-azido-l-ethanol

2-(Prop-2-ynyloxy)ethanol (9) was synthesized by refluxing ethylene glycol, propargyl bromide, and powdered sodium hydroxide for 16 hours. This highly volatile compound was obtained in 6% yield (Scheme 4).

^Hυ

Scheme 4 - Synthesis of 2-(Prop-2-vnvloxv)ethanol

Both l,3,4,6-Tetra-O-acetyl-j8-D-mannopyranose and 3,4,6-Tri-O-acetyl-2-hydroxyl- α-D-mannopyranosyl azide were synthesized from D-mannose following the reaction sequence detailed in Scheme 5.

Scheme 5

The treatment of (12) with HCl and acetone gave the selectively deprotected tetra acetylated D-mannose (13) with the hydroxyl group axial at the 2 position. This was achieved in 11% yield over the first 4 steps. Protection of the hydroxyl group was achieved with pentafluoropropanoic anhydride, yielding the 2-pentafluoropropionyl mannose derivative (14) in quantitative yield. Bromination at the anomeric position was again achieved through use of HBr in acetic acid to give the brominated analogue (15) in 90% yield. Trimethylsilyl azide and tetrabutylammonium fluoride were used to substitute the bromide for azide, however this step also resulted in the partial deprotection of the pentafluoropropionyl group. Thus, immediately after work up the full deprotection was carried out using pyridine in ethanol to give 3,4,6-tri-O- acetyl-2-hydroxy-α-D-mannopyranosyl azide (16) in 21% yield. The 3,4,6-tri-O- acetyl-2-O-pentafluoropropionyl-α-D-mannopyranosyl azide intermediate was used without purification.

The synthesis of N-(2-hydroxyethyl)phthalimide was carried out for its subsequent use as a precursor to the radiotracer [¹⁸F]fluoroetanidazole (FETA). A mixture of phthalic anhydride and ethylamine were heated to 125°C for 30 minutes, and then cooled to 5O⁰C and diluted with methanol. Further cooling to room temperature before addition of water resulted in the generation of N-(2-hydroxyethyl)phthalimide in a 57% yield (Scheme 6). mins

Scheme 6 - Synthesis of N-(2-hvdroxyethvDphthalimide

A sample of trøMs-Λf-(tørt-butoxycarbonyl)-4-hydroxyproline methyl ester was also selected to be tagged. Inversion of the stereochemistry of the hydroxyl group was achieved through a Mitsunobu reaction, thus enabling both diastereomers to be tagged. The inversion was achieved by mixing a solution of N-(tert-butoxycarbonyl)- trans-4-hydroxyproline methyl ester in THF with DIAD, triphenylphosphine, and acetic acid at room temperature. After inversion, the protected alcohol was immediately deprotected using potassium carbonate and methanol. The trans diastereomer was successfully inverted to the cis diastereomer in 45% yield (Scheme 7).

HO 1 ) DIAD, PPh₃, AcOH, THF HO

RT, 15h

COOMe C >- COOMe

N 2) K₂CO₃, MeOH, RT, Ih Boc Boc (18)45%

Scheme 7 - Mitsunobu Inversion Procedure

Tagging of Alcohols

A generic procedure used for the tagging of alcohols was followed, featuring the nucleophilic attack of the hydroxyl functionality onto the sulfonyl chloride, resulting in chloride displacement. Triethylamine was then used to capture the resultant HCl produced (Scheme 8).

Scheme 8 - Process for Fluorous Tagging This procedure was carried out on the alcohols (8, 9, 13, 16, 17 and 18) synthesized above, as well as some other selected commercially available alcohols.

Table 1

As a variation of the standard fluorous tagging process outlined above, ethylene glycol was doubly tagged on both hydroxyl groups using 2.2 equivalents of the slightly fluorous tag lH,lH,2H,2H-perfluorooctanesulfonyl chloride (Scheme 9).

Scheme 9 - Double Tagging of Ethylene Glycol

The white solid product resulting from this reaction was sparingly soluble in acetonitrile.

'Fluoro-detagging' of Prosthetic Groups

A number of the alcohols successfully tagged were to act, after fiuorination, as prosthetic groups for the synthesis of more complex radiotracers. Some radiotracers cannot withstand the harsh reaction conditions required for efficient and late [ F]- labelling in high radiochemical yields. In such cases, the molecule can be labelled through coupling with a small labelled prosthetic group via a much milder reaction, hi this context, a powerful transformation for labelling is the so-called 'click' reaction. The click reaction, also know as a Huisgen cycloaddition, is in essence a 1,3 dipolar cycloaddition between an azide and an alkyne. This process is catalysed by Cu(I), generated in situ through the reduction of Cu(II) in the form of CuSO₄, by sodium ascorbate.

The click reactions selected involve the ¹⁸F labelling of either the azide or alkyne species.

Another form of coupling reaction which can be used to join ¹⁸F radiolabeled prosthetic groups to their counterparts is a nucleophilic ring opening of an epoxide by attack of an amine (Scheme 10). R-NH_{2 +} °L>-_R " _R-AJ^_R

Scheme 10 - Coupling via an Epoxide Ring Opening

When carrying out fluorinations with ¹⁸F, the most commonly used technique for product analysis is HPLC. Therefore fully characterised 'cold' reference ¹⁹F-products are needed.

The process of fluorination using ¹⁸F required the preparation of 18-fluoride reagents so as to make it suitable for further use. This is illustrated schematically (Fig. 2).

The [¹⁸F]KF-kryptofix complex in MeCN solution was the ¹⁸F^" source used in all the radiolabelling processes carried out.

Nucleophilic Fluorination of Model Prosthetic Groups

For selected examples, ¹⁹F fluorination reaction was carried out first.

The fluorination of 2-azidoethyl IH, lH,2H,2H-perfluorodecane-l -sulfonate with caesium fluoride resulted in the production of l-azido-2-fluoroethane. This fiuorinated azide is a very versatile prosthetic group, suitable for click coupling onto terminal alkynes. The procedure adopted for the preparation and click coupling of 1- azido-2-fluoroethane with ¹⁹F is as follows (Scheme 11).

_r p

^{8 1}

Scheme 11 - Fluorous Preparation and Click Coupling of 1- Azido-2-fluoroethane

1 -Azido-2-fluoroethane obtained by nucleophilic fluorination was not isolated. It was separated from the remaining fluorous starting material using a 500mg FSPE cartridge, prepared according to standard procedures. After work-up, 300 μL of the crude product in MeCN solution up was diluted with 200 μL H₂O. The mixture was passed through the cartridge and washed with 500 μL ACN/H2O (7:3) and the fluorophobic filtrate containing the non-fluorous l-azido-2-fluoroethane (28) product was collected. The cartridge was further eluted with neat MeCN to recover excess starting material, and fluorous side products.

After FSPE purification, the l-azido-2-fluoroethane solution was used in a click reaction with the propargylic amide, N-(prop-2-ynyl) benzamide. This resulted in the production of 4-[l-(2-fluoroethyl)-lH-[l,2,3]triazol-4-yl]benzoic acid (29) in 74% yield.

Scheme 12 - Hot Fluorous Synthesis and Click Coupling of l-Azido-2-fluoroethane

Successful production of [¹⁸F]-fluoroethanazide (28') was achieved by use of

[¹⁸F]KF/kryptofix in anhydrous MeCN. An FSPE process separated the remaining fluorous starting material from the fluorinated product. To determine the • radiochemical yield, a click reaction with an aliquot of the crude compound was carried out with N-propargylbenzamide. This resulted in the production of [¹⁸F]N- Benzyl-3-[l-(2-fluoroethyl)-lH-[l,2,3]triazol-4-yl]propionamide. HPLC analysis confirmed the product to be the desired target, and radio-TLC indicated a 67% decay corrected RCY over two steps.

The synthesis of the ¹⁹F reference was to proceed firstly by click coupling of the tagged alkyne (20) with benzyl azide (30), followed by nucleophilic fluorination of the clicked-tagged intermediate (31) using TBAF (Scheme 13). This generated the 'cold' target compound which gave a major [M+H]⁺ peak at 236.1 in a low resolution mass spectrum.

Scheme 13 - Radiolabelling of an Alkyne Species

The fluoro-detagging was carried out first, using [¹⁸F]KF/kryptofix in anhydrous MeCN. After FSPE separation of 3-[¹⁸F](s-fluoroethoxy)prop-l-yne (32) which obtained the purified product in a solution of MeCNZH₂O (3:2), the click coupling was carried out with benzyl azide. Radio-TLC indicated a 79% RCY, and a HPLC retention time of 7.48 minutes was observed. This alternative route for the reactions with ¹⁸F demonstrates how the click coupling can, if necessary, be achieved after the fluoro-detagging step should the secondary click component be unstable to the fluorination conditions.

Following successful production of the fluorinated epoxide 2-fluoromethyl(oxirane), it was reacted with benzylamine in isopropanol for 5 hours at 80°C. This formed the coupled product l-(benzylamino)-3-fluoropropan-2-ol (32) in 90% yield (Scheme 17). In addition, the doubly-coupled side product 3,3'-(benzylazanediyl)bis(l- fluoropropan-2-ol) was found in trace quantities.

Scheme 14 - Coupling of 2-(fluoromethvDoxirane with Benzyl Amine

Application of this reaction sequence with ¹⁸F started from the fluorous precursor glycidyl lH,lH,2//,2H-perfluorodecylsulfonate (22). This was heated with

[¹⁸F]KF/kryptofix in anhydrous MeCN at 120°C for 15 minutes. The radiochemical yield was to be obtained via a coupling process with benzylamine. This was reacted with an aliquot of crude 2-[¹⁸F](fluoromethyl)oxirane at 80°C for 15 minutes. ΗPLC analysis gave a retention time of 8.55 minutes, matching that of the reference. Radio- TLC indicated complete conversion of the fluorinated epoxide to the target compound, and gave an 89% RCY over two steps (Scheme 15).

Scheme 15 - Hot Coupling with 2-[¹⁸F](fluoromethyl)oxirane

Purification of 2-[¹⁸F](fluoromethyl)oxirane by FSPE successfully separated the target product from the remaining fluorous material present in the crude reaction mixture. The purified compound was collected from the cartridge in a solution of MeCN/Η₂O (7:3) which was then used in subsequent reactions.

I S

As a final model example of prosthetic group labelling, an [ F]FDG-related precursor with an azide functionality at the 2 position had been synthesized. Radiofluorination by use of [¹⁸F]KF/kryptofix in anhydrous MeCN produced a single labelled species. Analysis by radio-TLC (EtOAc) indicated a 10% RCY (Scheme 16).

Scheme 16 - Hot Fluorination of Fluorous Glucose- Azide Species

The presence of an azide group leaves scope for potential click coupling reactions with species featuring a terminal alkyne.

'Fluoro-Detagging' to form Biorelevant Targets

The removal of a fluorous tag through a nucleophilic fluorination procedure has been used in the synthesis of a range of existing radiotracers. In some examples the fluoro- detagging step produces the labelled target tracer. Other cases utilize the technique of indirectly radiolabelling by a coupling process with a labelled prosthetic group.

Fluoromisonidazole (FMISO)

The radiotracer [¹⁸F]FMISO (39) is well established PET imaging agent, used for detection of hypoxic tissue in malignant tumour cells. Synthesis via a fluorous route was achieved through he reaction of FSPE purified 2-[ F](fluoromethyl)oxirane with 2 imidazole, using caesium bicarbonate, resulted in productionnidazole. Radio- TLC analysis indicated 53% RCY, and the HPLC retention time of 7.44 minutes compared to that of a purchased cold reference confirmed the successful labelling of the target compound (Scheme 17).

Scheme 17 - Synthesis of [¹⁸FIFMISO

l-Fluoro-3-(3-nitro-lH-l,2,3-triazol-l-yl)propan-2-ol

The reaction with 3-nitro-lH-l,2,4-triazole with the FSPE purified solution of 2- [¹⁸F](fluoromethyl)oxirane resulted in the formation of l-[¹⁸F]fluoro-3-(3-nitro-lH- l,2,4-triazol-l-yl)propan-2-ol (35). Analysis by radio-TLC indicated a 50% radiochemical yield. An ΗPLC retention time of 7.22 minutes confirmed the product to be the desired target compound (Scheme 18).

Scheme 18 - Synthesis Qf T¹⁸Fl (38')

Fluoroetanidazole (FETA)

[ F]-Fluoroetanidazole (FETA) is a PET imaging agent for hypoxic tumour cells. An existing synthetic route for [¹⁸F]FETA starts from N-[2-(toluene-4- sulphonyloxy)-ethyl]-phthalimide. Synthesis, from iV-(2-hydroxyethyl)phthalimide, of an analogous species with a fluorous tag in place of the tolyl functionality allowed for a fluorous method of production of [ F]FETA to be investigated. In this fluorous route, 2-phthalimidoethanol lH,lH,2H,2H-perfluorodecylsulfonate (23) was reacted with [¹⁸F]KF/kryptofix in anhydrous MeCN at 120°C for 15 minutes. This resulted in successful tagging to produce [¹⁸F]-N-(2-fluoroethyl)phthalimide (36) in 57% radiochemical yield as indicated by radio-TLC (Scheme 19).

Scheme 19 -Hot Fluoro-Detagging towards synthesis of [¹⁸F]FETA Purification was by FSPE. The crude product in MeCN solution (0.3mL) was diluted with H₂O (0.2mL) and passed through a 200mg FSPE cartridge, prepared according to standard procedures. The cartridge was washed with MeCN/H₂0 (7:3, 0.5mL) and the collected solution containing the purified fluorinated product was used in the production of 2-[ F]fluoroethylamine by a reaction with hydrazine. Analysis by TLC and HPLC indicated complete conversion of [¹⁸F] -N-(2-fluoroethyl)phthalimide (Scheme 20). The total decay-corrected radiochemical yield for the sequence as far as [¹⁸F]fluoroethanamine was 59%.

Scheme 20 - Production of 2-[¹⁸Flfluoroethylamine

Fluorodeoxyglucose (FDG)

An important example of the use of fluorous technologies in the 'fluoro-detagging' and purification of ¹⁸F-radiolabelled compounds is the synthesis of [¹⁸F]-FDG. Being one of the most widely known and commonly used radiotracers, this is an ideal candidate to demonstrate the potential of such fluorous methods of synthesis. Fluorination of the precursor, l,3,4,6-Tetra-O-acetyl-2-O-lH,lH,2H,2H- perfluorodecyl sulfonyl -β - mannopyranose (24), using the [¹⁸F]KF/kryptofix in anhydrous MeCN at 120⁰C for 15 minutes, resulted in the generation of a single fluorinated product (Scheme 21). Analysis by radio-TLC indicated a 12% RCY.

Scheme 21 -Hot Fluorination to form [¹⁸FIFDG C/s-4-Fluoro-L-proline

Synthesis, starting from the fluorous precursor trø«s-./V-(tert-butoxycarbonyl)-4- (lH,lH,2H,2H-perfluorodecanesulfoxy)proline methyl ester (25), required heating with [¹⁸F]KF/kryptofix at 120°C for 15 minutes (Scheme 22).

(25) (42) 38% RCY

Scheme 22 - Hot Fluorination of Proline Derivative

FSPE purification successfully separated the fluorinated product from remaining fluorous material. Analysis by ΗPLC and radio-TLC indicated a single fluorinated product had been produced in 38% RCY. Following this, the deprotection of the Boc and methyl ester groups was achieved to give cw-4-fluoroproline (40) was achieved using trifiic acid.

Specific Activity Study

An important factor requiring consideration when using radiotracers in vivo is the specific activity of the compound. This is defined as the level of radioactivity per unit quantity of tracer. To obtain a good quality PET image, the amount of radioactivity needs to be at a certain minimum level. In calculating the appropriate quantity of a radiotracer to use, the specific activity of the compound must be known. Also, for PET imaging agents with high toxicity levels, it is desirable to use a small amount of tracer with a high specific activity, than a larger quantity with a lower specific activity.

The study was carried out using the fluorination of both 4-phenylbutyl tosylate and 4-phenylbutyl lH,lH,2H,2H-perfluorodecane-l-sulfonate. These were both radiofluorinated using [¹⁸F]KF/kryptofix in anhydrous MeCN, and resulted in the production of [ F]4-phenylbutyl fluoride. This was achieved in 92%RCY from the tosyl starting material, and in 91% RCY from the fluorous precursor (Scheme 23).

Scheme 23 - Hot Fluorination to form [¹⁸F14-phenylbutyl fluoride

The HPLC was calibrated by running a range of cold samples of the fluorinated product in different concentrations. The area of the UV trace obtained from each sample was calculated by integration, and this allowed a correlation between concentration and area to be calculated. Having calibrated the apparatus, labelled samples of the fluorinated product were then run through the machine. The integration area of the UV traces obtained were compared to the non-labelled data, and the concentration of the sample could be ascertained. Prior to the HPLC analysis, the labelled samples were measured for their level of activity using a dosimeter. This activity was then related back to the calculated concentration, and hence the activity per mol of the fluorinated product could be obtained.

Standard Procedures

General: Solvents were dried prior to use according to procedures described by Pangborn and Grubbs. Flash column chromatographies were performed on silica gel using the method of Still. Analytical thin layer chromatography (TLC) was performed on Merck Silica gel 6- F₂₅₄ plates. Infrared spectra were recorded on a Bruker Tensor 27 FT-IR spectrometer and only peaks of interest are reported. Mass Spectra were recorded on a Micromass GCToF in Chemical Ionisation (NH₃, CI⁺) or Electron Impact (EI). High Resolution MS were obtained on a Bruker Datonics microTOF accurate ESI machine. Melting Points were recorded using Philip-Harris block and are uncorrected. °C^D = sample decomposed at this temperature. ¹H NMR spectra were recorded on a Bruker DPX200, AV400 or AVC500, ¹³C NMR spectra were recorded on a Bruker AV400 or AVC500, and ¹⁹FNMR spectra were recorded on a Bruker AV400. AU are internally referenced to solvent CDCl₃ unless otherwise specified, chemical shifts are reported in ppm, and coupling constants (J) are given in Hertz (Hz). Optical Rotations were recorded on a Perkin-Elmer 241 polarimeter. Solid Phase Extraction: FSPE separation was carried out using pre-assembled Waters Sep-Pak Cartridges or using FluoroFlash Silica gel. The cartridge were prepared by weighing out the specified mass of fluorous silica and filling the cartridge. The silica was then washed and packed by eluting with MeOH (4 mL/g silica), H₂O (20 mL/g silica), acetone (2 mL/g silica), THF (2 mL/g silica), MeOH (2 mL/g silica) and then immediately prior to use H₂O (2 mL/g silica). Pre-assembled Sep-Pak C₁₈SPE Cartridges were prepared in the same way.

Radiochemistry: Crude reaction mixtures were analysed by TLC and HPLC. HPLC was equipped with Nal-radiodetector and a specified column and solvent system.UV detection was carried out at a wavelength of 254 nm. Radio-TLC was performed on Macherey-Nagel Polygram Silica Plates and eluted with EtOAc or 95% aq. MeCN. Detection was with a plastic scintillator/PMT detector.

TLC provides a reliable way of calculating the radiochemical conversion except for volatile products. HPLC provides a reliable characterization of the labelled compound, but is not a reliable technique for calculating the radiochemical yield from as [ F] fluoride sticks on reversed phase columns. [¹⁸F]Fluoride was produced by the cyclotron of PETNET Solutions at Mont

Vernon Hospital (UK) via the ¹⁸O (p,n)¹⁸F reaction and delivered as [¹⁸F]Fluoride in [¹⁸O]water (1-2 GBq, 1-3 mL). This target solution was passed through a QMA anion exchange resin cartridge (20 mg, Waters). [¹⁸F]Fluoride adsorbed on the resin was eluted into a reaction vial with a solution of Kryptofix 222 (15 mg) and K₂CO₃ (3 mg) in 1 mL acetonitrile/water (8:2). Excess water was removed under N₂ stream at 100-11O⁰C, and the resulting complex was dried an additional 3 times by azeotropic distillation with 0.5 mL acetonitrile each under N₂ stream. The resulting dry complex of K¹⁸F/Kryptofix 222 is further dissolved by anhydrous acetonitrile (2-4 mL) and dispensed into reaction vials containing the precursor for nucleophilic fluorination. All quoted radiochemical yields are decay corrected. Experimental Procedures

4-Phenylbutyl fluoride (2)

In a sealed reaction vial, 0.3 niL of K¹⁸F/Kryptofix 222 in anhydrous MeCN (160 MBq) was added to 4-phenylbutyl tosylate (10 mg) and heated for 15 minutes at 120°C. The crude reaction mixture was diluted with 0.5 mL MeCN (138 MBq/mL), and analysis by HPLC (Zorbax SB, C18, 250 x 4.6 mm, MeCN/H₂0 (1 :9), 1 mL/min, 20 μL injected) gave a retention time of 12.40 minutes. Comparison with a cold reference HPLC trace confirmed the product to be the successfully labelled target compound. Analysis by radio-TLC (95% MeCN) indicated 92% RCY. The same procedure was carried out using 4-phenylbutyl IH,\H,2H,2H- perfluorodecylsulfonate (10 mg) to which was added 0.3 mL of K¹⁸F/Kryptofix 222 in anhydrous MeCN (140 MBq). The reaction mixture was heated for 15 minutes at 120°C in a sealed reaction vial. The same analysis procedure indicated production of the successfully labelled target compound in 91% RCY.

l^l^l/f^^-Perfluorodecyl thiouronium iodide (3)

In a 100 mL round bottomed flask, thiourea (1.54 g, 20.0 mmol) was added to a stirred solution of lH,lH,2H,2H-perfluorodecyl iodide (10.0 g, 17.4 mmol) in ethyl alcohol (17.0 mL). The mixture was left to reflux at 78°C for 9 hours under a nitrogen atmosphere before being cooled to room temperature. The solvent was removed under reduced pressure to reveal a cream/white solid (10.9 g, 16.8 mmol, 96% yield). This was used in the next step without further purification. l#,l/y,2iy,2/y-Perfluorodecyl sulfonyl chloride (4)

In a 250 mL round bottomed flask, IH,IH,2H,2H- perfluorodecyl thiouronium iodide (1.95 g, 3.0 mmol) was dissolved in a mixture of warm acetic acid (9.0 mL) and water (1.0 mL). Once dissolved, the solution was cooled to 10°C to get a homogeneous suspension. In a 250 mL round bottomed flask at 0°C, HCl (40.0 mL) was added dropwise to solid KMnO₄ (15.0 g, 94.9 mmol), releasing Cl₂ gas. The Cl₂ was bubbled through water, and then into the stirred suspension at a steady rate for 2.5 hours at 10⁰C. During this time the suspension changed from colourless to yellow. The mixture was then allowed to stir for a further hour under a flow of nitrogen, before the white solid was collected by filtration, washed with water, and dried under vacuum. (1.39 g, 2.55 mmol, 85% yield). This was used in subsequent reactions without further purification.

4-Phenylbutyl Ii7,l#,2/y,2i7-perfluor()decane-l-sulfonate (7)

In a 10 mL round bottomed flask, distilled triethylamine (0.08 mL, 0.6 mmol) followed by lH,lH,2H,2H-perfluorodecyl sulfonyl chloride (0.33 g, 0.6 mmol) were added to a stirred solution of 4-phenylbutan-l-ol (0.08 mL, 0.5 mmol) in DCM (2.0 mL) under a nitrogen atmosphere. The mixture was allowed to stir at room temperature for 6 hours before being quenched with water and extracted with DCM (3 x 15 mL). The combined organic phases were washed with brine and sodium bicarbonate solution, dried over MgSO₄, and the solvent was removed under reduced pressure to give a cloudy white solid. The crude product was purified by column chromatography on silica gel (13% EtOAc in hexane) to afford the desired product as a white solid (257 mg, 0.39 mmol, 78% yield).

1/T,liy,2#,2#-Perfluorooctyl thiouronium iodide (5)

In a 100 mL round bottomed flask, thiourea (1.13g, 14.8 mmol) was added to a stirred solution of lH,lH,2H,2H-perfluorooctyl iodide (3.62 mL, 14.8 mmol) in ethyl alcohol (14.0 mL). The mixture was left to reflux at 78°C for 13 hours under a nitrogen atmosphere then cooled to room temperature. The solvent was removed under reduced pressure to reveal a cream/white solid (8.10 g, 14.7 mmol, quantitative yield). This was used in the next step without further purification.

l#,l/y,2i7,2//-Perfluorooctyl sulfonyl chloride (6)

In a 250 mL round bottomed flask, 1H,1H,2H,2H- perfluorooctyl thiouronium iodide (4.13 g, 7.5 mmol) was dissolved in a mixture of warm acetic acid (22.5 mL) and water (2.5 mL). Once dissolved, the solution was cooled to 1O⁰C to obtain a homogeneous suspension. In a 250 mL round bottomed flask at 0°C, HCl (40.0 mL) was added dropwise to solid KMnO₄ (15.0 g, 94.9 mmol), releasing Cl₂ gas. The Cl₂ was bubbled through water, and then into the stirred suspension at a steady rate for 2 hours at 10⁰C. During this time the suspension changed from colourless to yellow. The mixture was then allowed to stir for a further hour under a flow of nitrogen, before being cooled in an ice bath. The target compound has a melting point close to room temperature. The cooling caused the target product to crash out as a white precipitate, which was quickly removed by filtration, and dried under vacuum (2.92 g, 6.54 mmol, 87% yield). This was used in subsequent reactions without further purification. 4-Phenylbutyl l/y,l#,2//,2/7-perfluorodecane-l-sulfoiiate (7)

In a 10 mL round bottomed flask, distilled triethylamine (0.08 niL, 0.6 mmol) followed by lH,lH,2//,2H-perfluorodecyl sulfonyl chloride (0.33 g, 0.6 mmol) were added to a stirred solution of 4-phenylbutan-l-ol (0.08 mL, 0.5 mmol) in DCM (2.0 mL) under a nitrogen atmosphere. The mixture was allowed to stir at room temperature for 6 hours before being quenched with water and extracted with DCM (3 x 15 mL). The combined organic phases were washed with brine and sodium bicarbonate solution, dried over MgSO₄, and the solvent was removed under reduced pressure to give a cloudy white solid. The crude product was purified by column chromatography on silica gel (13% EtOAc in hexane) to afford the desired product as a white solid (257 mg, 0.39 mmol, 78% yield).

2-Azidoethyl l/y,l#,2#,2_J/y-perfluorodecane-l-sulfoiiate (19)

To a 25 mL round bottomed flask, lH,lH,2H,2H-perfluorodecyl sulfonyl chloride (1.14 g, 2.1 mmol) was added to a solution of 2-hydroxyethanazide (0.4M solution in DCM, 7.9 mL, 3.2 mmol). The mixture was stirred at 0⁰C for 2 hours, then warmed to room temperature and stirred for a further 2.5 hours before being quenched with water and extracted with DCM (3 x 20 mL). The combined organic phases were washed with brine and sodium bicarbonate solution, dried over MgSO₄, and the solvent removed under reduced pressure. The crude solid product was purified via column chromatography on silica gel (10% EtOAc in hexane) to afford the target product as a white crystalline solid (1.09 g, 1.8 mmol, 87% yield).

2-(Prop-2-ynyloxy)ethyl-lfl^r,l^,27/,2^-perfluorodecane-l-sulfonate (20)

In a 25 mL round bottomed flask, distilled triethylamine (0.24 mL, 1.7 mmol) followed by lH,lH,2H,2H-perfluorodecane sulfonyl chloride (273 mg, 0.5 mmol) were added to a solution of 2-(prop-2-ynyloxy)ethanol (140 mg, 1.4 mmol) in DCM (3.0 mL) at 0°C under a nitrogen atmosphere. The mixture was allowed to stir for 3 hours before being quenched with NaHCO₃, extracted with DCM, and the organic phases dried over MgSO_4. The solvent was removed under reduced pressure to give a crude solid product. Purification by column chromatography on silica gel (15% Et₂O in hexane) afforded the target product as a white solid (71 mg, 0.12 mmol, 23% yield).

S^.ό-Tri-O-acetyl-l-O-l^li^l^.Z^-perπuorodecane sulfonyl-α-D- mannopyranosyl azide (21)

In a 25 mL round bottomed flask, distilled triethylamine (0.14 mL, 1.0 mmol) followed by lH,lH,2H,2H-perfluorodecyl sulfonyl chloride (273 mg, 0.5 mmol) were added to a solution of 3,4,6-Tri-O-acetyl-2-hydroxyl-α-D-mannopyranosyl azide (248 mg, 0.75 mmol) in DCM (3.0 mL) at O⁰C under a nitrogen atmosphere. The mixture was allowed to stir for 3 hours, before being quenched with NaHCO₃ solution, and extracted with DCM (3 x 20 mL). The combined organic phases were washed with water, brine, and NaHCO₃ solution, dried over MgSO₄, and the solvent removed under reduced pressure to give a crude oil product. Purification was done by FSPE. A 500 mg fluorous silica gel cartridge was prepared according to the general procedures. Approximately half the crude product was dissolved in 40 mL of fluorophobic eluent (20% H₂O in MeOH) and passed through the cartridge. The cartridge was further eluted with fluorophilic eluent (neat MeOH) to recover excess starting material. The process was repeated on the second half of the crude product with a clean cartridge. Removal of the solvent from the fluorophilic filtrate afforded the target product as a viscous brown oil (417 mg, 0.49 mmol, 65% yield).

Glycidyl l#,liJ,2#,2#-perfluorodecylsulfonate (22)

In a 25 mL round bottomed flask, distilled triethylamine (170 μL, 1.22 mmol) followed by IH, lH,2H,2H-perfluorodecyl sulfonyl chloride (547 mg, 1.0 mmol) were added to a stirred solution of (±)-glycidol (132 μL, 2.0 mmol) in DCM (5 mL) at 0⁰C under a nitrogen atmosphere. The mixture was allowed to stir for 3 hours whilst warming up to room temperature before being quenched with sodium carbonate solution and extracted with DCM (3 x 10 mL). The combined organic phases were washed with brine, dried over MgSO₄, and the solvent removed under reduced pressure. The crude solid was washed with Et₂O to afford the target compound as a white solid (425 mg, 0.73 mmol, 73% yield).

2-Phthalimidoethanol l#,l#,2#,2#-perfluorodecylsulfonate (23)

hi a 10 mL round bottomed flask, distilled triethylamine (84 μL, 0.60 mmol) followed by lH,lH,2H,2H-perfluorodecyl sulfonyl chloride (328 mg, 0.60 mmol) were added to a stirred solution of N-(2-hydroxyethyi)phthalimide (96 mg, 0.50 mmol) in DCM (3 mL) at O⁰C under a nitrogen atmosphere. The mixture was allowed to stir for 3 hours whilst warming up to room temperature before being quenched with sodium carbonate solution and extracted with DCM (3 x 10 mL). The combined organic phases were washed with brine, dried over MgSO₄, and the solvent removed under reduced pressure. The crude solid was washed with Et₂O to afford the target compound as a white solid (256 mg, 0.366 mmol, 73% yield).

l,3A6-Tetra-0-acetyl-2-0-l/T4#,2#,2#-perfliiorodecyl sulfonyl -β - mannopyranose (24)

In a 25 mL round bottomed flask, lH,lH,2H,2H-perfluorodecane sulfonyl chloride (1.64 g, 3.0 mmol) was added to a solution of D-Mannose(OAc)₄ (1.04 g, 3.0 mmol) in DCM (10.0 mL) at 0°C. Distilled triethylamine (0.48 mL, 3.5 mmol) was added dropwise, and the mixture allowed stir for 16 hours, warming up to room temperature over the first 2 hours. The crude reaction mixture was passed through a pad of silica, washed with DCM, and the solvent removed under reduced pressure to give a crude solid product. Purification by column chromatography on silica gel (5% MeOH in DCM) afforded the target product as a pale yellow crystalline solid (1.12 g, 1.30 mmol, 43% yield).

fra/is-A^-^rt-butoxycarbony^^^l/fjl^^/^lAT-perfluorodecanesulfoxy) proline methyl ester (25)

In a 10 mL round bottomed flask, distilled triethylamine (89 μL, 0.64mmol) was added to a solution of N-(tert-butoxycarbonyl)-(2S,4R)-4-hydroxy methyl ester (100 mg, 0.4 mmol) in DCM (2.0 mL) at 0°C under a nitrogen atmosphere. 1H,1H,2H,2H- perfluorodecane sulfonyl chloride (328 mg, O.βmmol) was added, and the mixture allowed to stir for 3 hours before being quenched with NaHCO₃ solution and extracted with DCM (4 x 20 mL). The combined organic phases were dried with MgSO₄, and the solvent removed under reduced pressure to give a white solid. This was purified via a precipitation in hot Et₂O to afford the target compound as a white solid which was separated by filtration (249 mg, 3.29 mmol, 83% yield).

Ethane-l,2-diyl bisCli^l^/^Ztf-perfluorooctylsulfonate) (27)

hi a 10 mL round bottomed flask, distilled triethylamine (0.34 mL, 2.4 mmol) followed by lH,lH,2H,2H-perfluorooctyl sylfonyl chloride (1.0 g, 2.24 mmol) were added to a stirred solution of ethylene glycol (56 μL, 1.0 mmol) in DCM (4 mL) under a nitrogen atmosphere at 0°C and allowed to stir for 24 hours whilst warming up to room temperature. The crude reaction mixture was filtered and a crude white solid product was collected. This was purified by a trituration process; the product was washed with cold MeCN and filtration afforded the target product as a white solid (581 mg, 0.65 mmol, 65% yield).

l-Azido-2-fluoroethane (28)

_F^N₃

In a sealed reaction vial, 0.3 mL of K¹⁸F/Kryptofix 222 in anhydrous MeCN (20-100 MBq) was added to 2-azidoethyl IH, lH,2H,2H-perfluorodecane-l -sulfonate (10 mg) and heated for 15 minutes at 120⁰C. Determination of the radiochemical yield was by a further reaction. An aliquot (10 μL) of the crude reaction mixture was combined with iV-propargylbenzamide (5 mg), CuSO₄(_aq)(50 μL) and sodium ascorbate(_aq) (50 μL) and heated for 15 minutes at 80°C. Analysis by ΗPLC (Zorbax SB, C 18, 250 x 4.6 mm, MeCNZH₂O gradient, 1 mL/min) gave a retention time of 6.70 minutes. Comparison with the cold reference HPLC trace confirmed the product to be successfully labelled [' ⁸F]7V-Benzyl-3-[ 1 -(2-fluoroethyl)- 1 H-[ 1 ,2,3]triazol-4- yljpropionamide (29). Analysis by radio-TLC (EtOAc) indicated a 67% RCY.

2-[(l-Benzyl-lH-l,2,3-triazol-4-yl)methoxy]ethyl 1H,IH,2H,2H- perfluorodecylsulfonate (31)

In a 5 mL round bottomed flask, benzyl azide (0.07 mg, 0.05 mmol) was added to a stirred solution of 2-(prop-2-ynyloxy)ethyl- IH, 1 H,2H,2H-perfluorodecane- 1 - sulfonate (25 mg, 0.04 mmol) in DMF (1 mL). CuSO_4(aq) (60 μL of 0.45M solution, 0.05 mmol) and Na ascorbate(_aq)(15 μL of 1.5M solution, 0.05 mmol) were added, and the mixture allowed to stir at room temperature for 13 hours. The reaction was then quenched with water and extracted with DCM (3 x 2 mL). The combined organic phases were then washed with brine and sodium bicarbonate solution, dried over MgSO₄, and the solvent removed under reduced pressure. This afforded the target product as a yellow/white solid (23 mg, 0.03 mmol, 77% yield). This was used in the next step without further purification.

3-[¹⁸F](2-Fluoroethoxy)prop-l-yne (32)

In a sealed reaction vial, 0.3 mL of K¹⁸F/Kryptofix 222 in anhydrous MeCN (20-100 MBq) was added to 2-(prop-2-ynyloxy)ethyl-lH,lH,2H,2H-perfluorodecane-l- sulfonate (lOmg) and heated for 15 minutes at 120⁰C. Determination of the radiochemical yield was by a further reaction. An aliquot (10 μL) of the crude reaction mixture was combined with benzyl azide (5 mg), CuSO_4(aq) (50 μL) and sodium ascorbate_(aq) (50 μL) and heated for 15 minutes at 80°C. Purification of the successfully fluorinated product was by FSPE; the crude reaction mixture in MeCN (0.3 mL) was diluted with H₂O (0.2 niL) and eluted through a fluorous silica cartridge (200mg) which had been prepared according to the standard procedures. The cartridge was washed with MeCN/H₂0 (7:3, 0.5 mL) and the solution containing the purified product was collected. Analysis by HPLC (Zorbax SB, Cl 8, 250 x 4.6 mm, MeCN/H₂O gradient, 1 mL/min) gave a retention time of 7.48 minutes. Analysis by radio-TLC (EtOAc) indicated a 79% RCY.

[¹⁸F] l-benzyl-4-((2-fluoroethoxy)methyl)-lH-l,2,3-triazole (33)

In a sealed reaction vial, the FSPE purified solution of 3-[¹⁸F](2-Fluoroethoxy)prop- 1-yne (20-100 MBq) in MeCN/H₂0 (7:3, 0.5 mL) was reacted with benzyl azide (5 mg), CuSO₄(_aq) (50 μL) and sodium ascorbate(_aq) (50 μL) and heated for 15 minutes at 8O⁰C. Analysis by HPLC (Zorbax SB, C 18, 250 x 4.6 mm, MeCN/H₂O gradient, 1 mL/min) gave a retention time of 7.48 minutes. Analysis by radio-TLC (EtOAc) indicated a 79% RCY.

2-(Fluoromethyl)oxirane (34)

In a sealed reaction vial, 0.3 mL of K¹⁸F/Kryptofix 222 in anhydrous MeCN (20-100 MBq) was added to glycidyl lH,lH,2H,2H-perfluorodecylsulfonate (lOmg) and heated for 15 minutes at 12O⁰C. Purification was done by FSPE; the crude product in MeCN (0.3 mL) was diluted with H₂O (0.2 mL) and eluted through a fluorous silica cartridge (200mg) which had been prepared according to the standard procedures. The cartridge was washed with MeCN/H₂0 (7:3, 0.5 mL) and the collected solution containing the purified product was used in subsequent reactions. Analysis by HPLC (Zorbax SB, C 18, 250 x 4.6 mm, MeCN/H₂O (1:9), 1 mL/min) gave a retention time of 4.76 minutes.

l-(Benzylamino)-3-fluoropropan-2-ol (35)

In a sealed 5 mL reaction vial, epifluorohydrin (0.6 mL of 0.165M solution in CDCl₃, 0.1 mmol) was added to a solution of benzylamine (22 μL, 0.2 mmol) in isopropanol (0.5 mL) and was heated at 80°C for 5 hours. The solvent was removed under reduced pressure and purification by column chromatography on silica gel (5% MeOH in DCM) afforded the target product as a pale yellow oil (18 mg, 0.09 mmol, 90% yield) along with traces of 3,3'-(benzylazanediyl)bis(l-fluoropropan-2-ol).

In a sealed reaction vial an aliquot (10 μL) of crude 2-[¹⁸F](fluoromethyl)oxirane in anhydrous MeCN was reacted with benzylamine (5 μL) for 15 minutes at 80°C. Analysis by HPLC (Zorbax SB, Cl 8, 250 x 4.6 mm, MeCN/H₂O gradient, 1 mL/min) gave a retention time of 8.55 minutes. Comparison with a cold reference HPLC trace confirmed the product to be the successfully labelled target compound. Analysis by radio-TLC (EtOAc) indicated 89% RCY.

3,4,6-Tri-0-acetyl-2-fluoro-a-D-mannopyranosyl azide (36)

In a sealed reaction vial, 0.3 mL of K¹⁸F/Kryptofix 222 in anhydrous MeCN (20-100 MBq) was added to 3 ,4,6-Tri-O-acetyl-2-O-lH,lH,2H,2H-perfluorodecane sulfonyl- α-D-mannopyranosyl azide (10 mg) and heated for 15 minutes at 120°C. Analysis of the crude product by radio-TLC (EtOAc) indicated a 10% RCY. Purification of 3,4,6-Tri-O-acetyl-2-fluoro-α-D-mannopyranosyl azide (34) was by FSPE; the crude reaction mixture (0.3 mL) was diluted with H₂O (0.2 mL) and eluted through a fluorous silica cartridge (200mg) which had been prepared according to the standard procedures. The cartridge was washed with MeCN/H₂0 (7:3, 0.5 mL) and the solution containing the purified product was collected.

Fluoromisonidazole (FMISO) (37)

hi a sealed reaction vial, purified 2-[¹⁸F](fluoromethyl)oxirane in MeCN/H₂0 (7:3) solution (0.5 mL) was added to 3-nitro-lH-l,2,4-triazole (5 mg) and caesium carbonate (5 mg) and heated to 8O⁰C for 15 minutes. Analysis by ΗPLC (Zorbax SB, C18, 250 x 4.6 mm, MeCN/Η₂0 (1:9), 1 mL/min) gave a retention time of 7.44 minutes. Comparison with a cold reference HPLC trace confirmed the product to be the successfully labelled target compound. Analysis by radio-TLC (EtOAc) indicated 53% RCY.

l-[¹⁸F]Fluoro-3-(3-nitro-lH-l,2,4-triazoI-l-yl)propan-2-ol (38)

hi a sealed reaction vial, purified 2-[¹⁸F](fluoromethyl)oxirane in MeCN/H₂0 (7:3) solution (0.5 mL) was added to 2-imidazole (5 mg) and caesium carbonate (5 mg) and heated to 80°C for 15 minutes. Analysis by HPLC (Zorbax SB, C 18, 250 x 4.6 mm, MeCN/H₂0 (1 :9) 1 mL/min) gave a retention time of 7.22 minutes. Comparison with a cold reference HPLC trace confirmed the product to be the successfully labelled target compound. Analysis by radio-TLC (EtOAc) indicated 50% RCY.

[¹⁸F]-/V-(2-FluoroethyI)phthalimide (39)

In a sealed reaction vial, 0.3 niL of K¹⁸F/Kryptofix 222 in anhydrous MeCN (20-100 MBq) was added to 2-phthalimidoethyl lH,lH,2H,2H-perfluorodecylsulfonate (lOmg) and heated for 15 minutes at 120°C. Purification was by FSPE; the crude product in MeCN (0.3 mL) was diluted with H₂O (0.2 niL) and eluted through a fluorous silica cartridge (200mg) which had been prepared according to the standard procedures. The cartridge was washed with MeCN/H₂0 (7:3, 0.5 mL) and the collected solution containing the purified product was used in a subsequent reaction. Analysis by HPLC (Zorbax SB Cl 8 250 x 4.6 mm, MeCN/H₂0 gradient, 1 niL/min) gave a retention time of 9.01 minutes. Comparison with a cold reference HPLC trace confirmed the product to be the successfully labelled target compound. Analysis by radio-TLC (EtOAc) indicated 57% RCY.

[¹⁸F]Fluoroetanamine (40)

H₉N.

In a sealed reaction vial, purified [¹⁸F]-N-(2-fiuoroethyl)phthalimide in MeCN/H2O (7:3) solution (0.5 mL) was added to hydrazine (1 μL) and heated to 70⁰C for 10 minutes to generate [^I8F]-2-fluoroethanamine (41). Analysis radio-TLC (EtOAc) indicated complete conversion to the labelled target product.

[¹⁸F]Fluorodeoxyglucose (FDG) (41)

In a sealed reaction vial, 0.3 mL of K¹⁸F/Kryptofix 222 in anhydrous MeCN (120 MBq) was added to l,3,4,6-tetra-O-acetyl-2-O-lH,lH,2H,2H-perfiuorodecyl sulfonyl - mannopyranose (lOmg) and the mixture was heated for 15 minutes at 120°C. Purification was by FSPE; the crude product in MeCN (0.3 mL) was diluted with H₂O (0.2 mL) and eluted through a fluorous silica cartridge (200mg) which had been prepared according to the standard procedures. The cartridge was washed with MeCN/H₂O (7:3, 0.5 mL) and the collected solution containing the purified product was collected. Analysis by radio-TLC (EtOAc) indicated production of [¹⁸F]Fluorodeoxyglucose (43) in 12% RCY.

Λ^tert-butoxycarbonyl)-(2S,4S)-4-fluoropr()Iine methyl ester (42) and Cis-4-fluoro-L-proIine (43)

In a sealed reaction vial, 0.3 mL of K¹⁸F/Kryptofix 222 in anhydrous MeCN (20-100 MBq) was added to N-(tert-butoxycarbonyl)-(2S,4R)-4-lH,lH,2H,2H- perfluorodecylsufonyloxy methyl ester (lOmg) and heated for 15 minutes at 120⁰C. Purification was by FSPE; the crude product in MeCN (0.3 mL) was diluted with

H₂O (0.2 mL) and eluted through a fluorous silica cartridge (200mg) which had been prepared according to the standard procedures. The cartridge was washed with MeCN/H₂O (7:3, 0.5 mL) and the solution containing the purified product was collected and used in the subsequent deprotection. Analysis by HPLC (Zorbax SB Cl 8 250 x 4.6 mm MeCN/H₂O gradient, 1 mL/min) gave a retention time of 9.43 minutes. Comparison with a cold reference HPLC trace confirmed the product to be the successfully labelled target compound (44). Analysis by radio-TLC (EtOAc) indicated 38% RCY. In a sealed reaction vial, purified 7V-(tert-butoxycarbonyl)-(2S,4S)-4-fluoroproline methyl ester in MeCN/H₂0 (7:3) solution (0.5 mL) was added to triflic acid (50 μL of 2M solution) and heated for 15 minutes at 100°C. Analysis by HPLC (Phenomenex Selectosil, 5 NH₂, 250 x 4.6 mm, 5u, MeCN/lOmM phosphate buffer pH 7.0, 1:1) gave a retention time of 3.45 minutes. Comparison with a cold reference HPLC traces for cw-4-fluoro-L-proline and traMs-4-fluoro-L-proline confirmed the product to be the successfully labelled cis target compound. Analysis by radio-TLC (EtOAc) indicated complete deprotection.

Claims

1. A process for producing a fluorine-labelled compound, the process comprising:

(a) treating a compound of formula (I)

wherein: R¹, R² and the C(H) group to which R¹ and R² are bonded together form a moiety to be labelled with fluorine; and fluorous tag is a group of formula (II)

wherein Rf is a straight-chained or branched C_4-I2 perfluoroalkyl group; and L is a single bond, -alk-, -arylene-, -alk-arylene-, alk-X-, -arylene-X-, -alk- arylene-X, -alk-X-arylene-, -alk-X-arylene-X-, -arylene-alk-, -arylene-X-alk-, -arylene-alk-X- or -arylene-X-alk-X-, wherein X is N(R"), O, S, C(O) or C(O)N(R") and wherein alk is unsubstituted or substituted C_1-I0 alkylene which is optionally interrupted by N(R"), O, S, C(O), C(O)N(R") or arylene, wherein R" is Ci_-6 alkyl or aryl; with [ⁿF]^~, wherein "F is ¹⁸F or ¹⁹F, thereby fluorinating and detagging the compound of formula (I) to produce a fluorine-labelled compound of formula (III)

wherein R 1 1 a „„n.d j T R) 2 are as defined above for formula (I).

2. A process according to claim 1 further comprising: (b) separating the compound of formula (III) from one or more fluorous compounds which comprise Rf.

3. A process according to claim 2 wherein step (b) comprises separating the compound of formula (III) from said one or more fluorous compounds by Fluorous Solid Phase Extraction.

4. A process according to claim 2 or claim 3 wherein step (b) comprises (i) loading the reaction mixture onto a fluorous solid phase, and (ii) selectively eluting the compound of formula (III) from said fluorous solid phase such that said one or more fluorous compounds comprising Rf are retained on the solid phase.

5. A process according to any one of the preceding claims wherein the process further comprises recovering said compound of formula (III).

6. A process according to any one of claims 1 to 5 wherein: R² is H and R¹ is a group of formula (VI)

wherein L' is a single bond or -alk-, wherein -alk- is as defined in claim 1 , and R³ is H, unsubstituted or substituted Ci_-6 alkyl, aryl or an amine protecting group; or R² is H and R¹ is a group of formula (VII)

wherein L' is a single bond or -alk-, wherein -alk- is as defined in claim 1 ; or R² is H and R¹ is a group of formula (VIII)

wherein L' is a single bond or -alk-, wherein -alk- is as defined in claim 1, and X² is a halo group; or R² is H and R¹ is a group of formula (IX)

wherein L' is a single bond or -alk-, wherein -alk- is as defined in claim 1, R⁴ is unsubstituted or substituted Ci_-6 alkyl, aryl or an amine protecting group and R⁵ is unsubstituted or substituted Ci_-6 alkyl, aryl, acyl or a carboxyl protecting group; or R² is H and R¹ is a group of formula (X)

wherein L' is a single bond or -alk-, wherein -alk- is as defined in claim 1, and R⁶ is H, unsubstituted or substituted Ci_-6 alkyl, aryl or an amine protecting group; or

R² is H and R¹ is a group of formula (XI)

wherein L' is a single bond or -alk-, wherein -alk- is as defined in claim 1, and R and R are independently selected from H, unsubstituted or substituted C_1-6 alkyl, aryl or an amine protecting group; or

R² is H and R¹ is a group of formula (XII)

wherein L' is a single bond or -alk-, wherein -alk- is as defined in claim 1, R is unsubstituted or substituted Ci_-6 alkyl, aryl or an amine protecting group and R¹⁰ is is unsubstituted or substituted C_1-6 alkyl, aryl, acyl or a hydroxyl protecting group; or R¹, R² and the C(H) group to which R¹ and R² are both bonded together form a group of formula (XIII)

(XIV); or R¹, R² and the C(H) group to which R¹ and R² are both bonded together form a group of formula (XV)

wherein R¹³, R¹⁴, R¹⁵ and R¹⁶ are the same or different and are independently selected from acyl, unsubstituted or substituted Cj_-6 alkyl, aryl, or a hydroxyl protecting group; or

wherein R¹⁷, R¹⁸ and R¹⁹ are the same or different and are independently selected from acyl, unsubstituted or substituted Ci_-6 alkyl, aryl, or a hydroxyl protecting group; or

(XVIII) wherein R²² is an amine protecting group; or R² is H and R¹ is -alk-N₃, wherein -alk- is as defined in claim 1 ; or R² is H and R¹ is -alk-C ≡CH, wherein -alk- is as defined in claim 1 ; or R² is H and R¹ is -alk-CH=CH₂, wherein -alk- is as defined in claim 1 ; or R² is H and R¹ is -alk-R²³, wherein -alk- is as defined in claim 1 and R²³ is substituted or unsubstituted aryl; or

R² is H and R¹ is a group of formula (XIX)

wherein L² is -alk-, wherein -alk- is as defined in claim 1 and z is 0 or 1 ; or R² is H and R¹ is a group of formula (XX)

wherein L³ is -alk- or -alk-arylene-, wherein -alk- is as defined in claim 1 and z is 0 or 1 ; or

R² is H and R¹ is a group of formula (XXI)

wherein L⁴ is -alk- or -alk-arylene-, wherein -alk- is as defined in claim 1 and z is 0 or 1 ; or R² is H and R¹ is a group of formula (XXIV)

3 — L⁵— O — ( second fluorous tag) fXXTV_")

wherein L⁵ is -alk-, wherein -alk- is as defined in claim 1, and wherein the second fluorous tag is a group of formula (XXV)

wherein Ri ^nd is a straight-chained or branched C_4-12 perfluoroalkyl group, provided that the total number of carbon atoms in Rf and Rf^nd together does not exceed 12, and

L^2nd is a single bond, -alk-, -arylene-, -alk-arylene-, alk-X-, -arylene-X-, -alk- arylene-X, -alk-X-arylene-, -alk-X-arylene-X-, -arylene-alk-, -arylene-X-alk-, -arylene-alk-X- or -arylene-X-alk-X-, wherein X is N(R"), O, S, C(O) or C(O)N(R") and wherein alk is as defined in claim 1.

7. A process according to any one of the preceding claims wherein R¹, R² and the C(H) group to which R¹ and R² are bonded together form (i) a tracer moiety, (ii) a moiety which is a precursor to a tracer moiety, or (iii) a labelling agent moiety, which labelling agent moiety comprises a functional group suitable for attaching the compound of formula (III) to a tracer moiety or to a precursor of a tracer moiety.

8. A process according to claim 7 wherein R¹, R² and the C(H) group to which R¹ and R² are bonded together form said labelling agent moiety which comprises a functional group, and the process further comprises: (c) attaching to the compound of formula (III) a tracer moiety or a moiety which is a precursor of a tracer moiety, thereby producing a further compound of formula (III) which comprises a tracer moiety or a moiety which is a precursor of a tracer moiety.

9. A process according to claim 8 wherein step (c) comprises attaching to the compound of formula (III) a moiety which is a precursor of a tracer moiety, and the process further comprises:

(d) converting said moiety which is a precursor into said tracer moiety, thereby producing a further compound of formula (III) which comprises a tracer moiety.

10. A process according to any one of claims 1 to 8 wherein R² is H and R¹ is a group of formula (XIX)

wherein L² is -alk-, wherein -alk- is as defined in claim 1 and z is 0 or 1 ; and the process comprises:

H N_N R²⁶ (XXVI) wherein either (i) R²⁵ and R²⁶ and the NH group to which R²⁵ and R²⁶ are bonded together form an unsubstituted or substituted C_3-7 heterocyclyl group, or (ii) R²⁶ is hydrogen and R²⁵ is unsubstituted or substituted Cj_-2O alkyl, aryl, -alk- Ar, a tracer moiety or a precursor of a tracer moiety, wherein alk is as defined in claim 1 and Ar is aryl; and thereby producing a compound of formula (XXVII)

(XXVII).

11. A process according to claim 10 wherein ⁿF is ¹⁸F, z is 0, the amine of formula (XXVI) is:

and the compound of formula (XXVII) produced is:

[¹⁸F]FMISO.

12. A process according to claim 10 wherein ⁿF is ¹⁸F, z is 0, the amine of formula (XXVI) is:

and the compound of formula (XXVII) produced is:

13. A process according to any one of claims 1 to 8 wherein R² is H and R¹ is -alk-N₃, wherein alk is as defined in claim 1, and the process further comprises:

(c) treating the fluorine-labelled compound of formula (III) with an alkyne of formula (XXVIII) HC ≡€-R²⁷ (XXVIII)

wherein R²⁷ is -alk-N(R")-C(O)-R²⁸, -alk-R²⁹, -alk-C(O)-R²⁹, -C(O)-R²⁹, a tracer moiety, or a moiety which is a precursor to a tracer moiety, wherein alk is as defined in claim 1, R" is H, Ci_-6 alkyl or aryl, R²⁸ is unsubstituted or substituted Ci_-20 alkyl or aryl, and R²⁹ is a group which comprises a peptide or amino acid residue, and thereby producing a compound of formula (XXIX)

(XXIX).

14. A process according to any one of claims 1 to 8 wherein R¹, R² and the C(H) group to which R¹ and R² are both bonded together form a group of formula (XVI)

wherein R¹⁷, R¹⁸ and R¹⁹ are the same or different and are independently selected from acyl, unsubstituted or substituted C_1-6 alkyl, aryl, or a hydroxyl protecting group, and the process comprises:

(c) treating the fluorine-labelled compound of formula (III) with an alkyne of formula (XXVIII)

HC ≡C-R²⁷ (XXVIII)

wherein R²⁷ is -alk-N(R")-C(O)-R²⁸, -alk-R²⁹, -alk-C(O)-R²⁹, -C(O)-R²⁹, a tracer moiety, or a moiety which is a precursor to a tracer moiety, wherein alk is as defined in claim 1, R" is H, Ci_-6 alkyl or aryl, R²⁸ is unsubstituted or substituted C_1-20 alkyl or aryl, and R²⁹ is a group which comprises peptide or amino acid residue, and thereby producing a compound of formula (XXX)

15. A process according to any one of claims 1 to 8 wherein R² is H and R¹ is -alk-N₃, wherein alk is as defined in claim 1, and the process comprises:

wherein R³⁰ is Ci_-6 alkyl or aryl, L⁸ and L⁹, which are the same or different, are -alk-, wherein alk is as defined in claim 1, z is 0 or 1, and R³¹ is a group which comprises a peptide or amino acid residue, a tracer moiety, or a moiety which is a precursor to a tracer moiety, and thereby producing a compound of formula (XXXII)

(XXXII).

16. A process according to any one of claims 1 to 8 wherein R¹, R² and the C(H) group to which R¹ and R² are both bonded together form a group of formula (XVI)

wherein R¹⁷, R¹⁸ and R¹⁹ are the same or different and are independently selected from acyl, unsubstituted or substituted Ci_-6 alkyl, aryl, or a hydroxyl protecting group, and the process further comprises: (c) treating the fluorine-labelled compound of formula (III) with a compound of formula (XXXI)

wherein R³⁰ is Ci_-6 alkyl or aryl, L⁸ and L⁹, which are the same or different, are -alk-, wherein alk is as defined in claim 1, z is 0 or 1, and R³¹ is a group which comprises a peptide or amino acid residue, a tracer moiety, or a moiety which is a precursor to a tracer moiety, and thereby producing a compound of formula (XXXIII)

(XXXIII).

17. A process according to any one of claims 1 to 9 wherein R² is H and R¹ is a group of formula (XX)

wherein L³ is -alk- or -alk-arylene-, wherein -alk- is as defined in claim 1 and z is 0 or 1, and the process comprises:

(XXXIV).

18. A process according to claim 17, which comprises:

(d) treating the compound of formula (XXXIV) thus produced with an ester of formula (XXXV)

wherein R³³ is unsubstituted or substituted C_3-7 heterocyclyl, a group which comprises a peptide or amino acid residue, a tracer moiety, or a moiety which is a precursor to a tracer moiety, L¹⁰ is -alk-, wherein alk is as defined in claim 1, a is 0 or 1, and R³² is unsubstituted or substituted Ci_-10 alkyl or unsubstituted or substituted aryl, and thereby producing a compound of formula (XXXVI)

(XXXVI).

19. A process according to claim 18, wherein ⁿF is ¹⁸F, a is 1, L¹⁰ is a methylene group, z is 1, L³ is a methylene group, R³³ is

NO₂

N A N A^⁷ \_/ and the compound of formula (XXXVI) is

20. A process according to any one of claims 1 to 8 wherein R² is H and R¹ is -alk-C ≡CH, wherein -alk- is as defined in claim 1, and the process further comprises:

N₃-R³⁴ (XXXVII)

wherein R³⁴ is -alk-R³⁵, -alk-C(O)-R³⁵, -C(O)-R³⁵, a tracer moiety, or a moiety which is a precursor to a tracer moiety, wherein alk is as defined in claim 1 and R³⁵ is unsubstituted or substituted Ci_-20 alkyl, aryl, or a group which comprises a peptide or an amino acid residue, and thereby producing a compound of formula (XXXVIII)

(XXXVIII).

21. A process according to any one of claims 1 to 8 wherein R² is H and R¹ is a group of formula (XXIV) > — L⁵ — O — ( second f luorous tagj , „

wherein Rf^2nd is a straight-chained or branched C_4-I2 perfluoroalkyl group, provided that the total number of carbon atoms in Rf and Rf²"⁰ together does not exceed 12, and L^2nd is a single bond, -alk-, -arylene-, -alk-arylene-, alk-X-, -arylene-X-, -alk- arylene-X, -alk-X-arylene-, -alk-X-arylene-X-, -arylene-alk-, -arylene-X-alk-, -arylene-alk-X- or -arylene-X-alk-X-, wherein X is N(R"), O, S, C(O) or C(O)N(R") and wherein alk is as defined in claim 1, and the process comprises:

(XXXX)

22. A process according to claim 21 wherein ⁿF is ¹⁸F, L⁵ is CH₂, X² is either Cl or I and the compound of formula (XXXX) produced is either

[ 1-1¹8⁶F]FECNT or

23. A process according to any one of claims 1 to 8 wherein R² is H and R¹ is a group of formula (XXIV)

i — L⁵ — O second f luorous tag)

(XXIV)

(XXV) wherein Rf²"*¹ is a straight-chained or branched C_4-I2 perfluoroalkyl group, provided that the total number of carbon atoms in Rf and Rf²"¹¹ together does not exceed 12, and

L^2nd is a single bond, -alk-, -arylene-, -alk-arylene-, alk-X-, -arylene-X-, -alk- arylene-X, -alk-X-arylene-, -alk-X-arylene-X-, -arylene-alk-, -arylene-X-alk-, -arylene-alk-X- or -arylene-X-alk-X-, wherein X is N(R"), O, S, C(O) or C(O)N(R") and wherein alk is as defined in claim 1, and wherein the process comprises: (c) treating the fluorine-labelled compound of formula (III) with a compound of formula (XXII)

(XXIII); or

(XXXXII); or

1 o36 (XXXXIII) wherein R³⁶ is unsubstituted or substituted C_3-7 heterocyclyl, a tracer moiety, a group which is a precursor to a tracer moiety, a group which comprises a peptide or a group which comprises an amino acid residue, and L¹¹ is a single bond or -alk-, wherein alk is as defined in claim 1, and thereby producing a compound of formula (XXXXIV)

(XXXXIV).

24. A process according to any one of claims 1 to 8 wherein R² is H and R¹ is a group of formula (XXI)

wherein L⁴ is -alk- or -alk-arylene-, wherein -alk- is as defined in claim 1 and z is 0 or 1, and the process comprises:

(c) treating the fluorine-labelled compound of formula (III) with a thiol of formula (XXXXV) HS-L¹²-R³⁷ (XXXXV)

wherein L is a single bond, -alk- or arylene and R is a tracer moiety, a group which is a precursor to a tracer moiety, a group which comprises a peptide or a group which comprises an amino acid residue, and thereby producing a compound of formula (XXXXVI)

(XXXXVI).

25. A process according to any one of claims 1 to 7 wherein R¹, R² and the C(H) group to which R¹ and R² are bonded together form a moiety which is a precursor to a tracer moiety, and the process further comprises:

26. A process according to claim 25 wherein

wherein R¹³, R¹⁴, R¹⁵ and R¹⁶ are the same or different and are independently selected from acyl, unsubstituted or substituted Ci_-6 alkyl, aryl, or a hydroxyl protecting group, and the process comprises: (c) deprotecting the fluorine-labelled compound of formula (III) and thereby producing said further compound of formula (III) which is a compound of formula (XXXXXI)

n^fI (XXXXXI); or

R² is H and R¹ is a group of formula (VI)

(VI) wherein L' is a single bond or -alk-, wherein -alk- is as defined in claim 1, and R³ is H, unsubstituted or substituted Ci_-6 alkyl, aryl or an amine protecting group, and the process comprises:

(XXXXVII); or

R² is H and R¹ is a group of formula (IX)

H₂N (XXXXVIII); or

R² is H and R¹ is a group of formula (X)

(X) wherein L' is a single bond or -alk-, wherein -alk- is as defined in claim 1, and R⁶ is H, unsubstituted or substituted C_1-6 alkyl, aryl or an amine protecting group, and the process comprises:

(c) deprotecting the fluorine-labelled compound of formula (III) and thereby producing said further compound of formula (III) which is a compound of formula (XXXXIX)

(XXXXIX); or

R² is H and R¹ is a group of formula (XI)

wherein L' is a single bond or -alk-, wherein -alk- is as defined in claim 1, and R⁷ and R⁸ are independently selected from H, unsubstituted or substituted Ci_-6 alkyl, aryl or an amine protecting group, and the process comprises:

(XXXXX); or

R¹ , R² and the C(H) group to which R¹ and R² are both bonded together form a group of formula (XIII)

wherein R¹¹ is unsubstituted or substituted Ci_-6 alkyl, aryl, acyl or a hydroxyl protecting group and R¹² is unsubstituted or substituted C_1-6 alkyl, aryl or an amine protecting group, and the process comprises:

πF (XXXXXI); or

wherein R²⁰ is H, unsubstituted or substituted Ci_-6 alkyl, aryl, acyl or a hydrox :yyll pprrootteeccttiinngg ggrroouupp aanndd RR²²¹¹ iiss HH,, uunnssuubbssttiittuutteedd oorr ssubstituted Ci_-6 alkyl, aryl or an amine protecting group, and the process comprises: (c) deprotecting the fluorine-labelled compound of formula (III) and thereby producing said further compound of formula (III) which is a compound of formula (XXXXXII)

(XXXXXII); or

(XVIII) wherein R²² is an amine protecting group, and the process comprises: (c) deprotecting the fluorine- labelled compound of formula (III) and thereby producing said further compound of formula (III) which is a compound of formula (XXXXXII)

(XXXXXII).

27. A process according to any one of the preceding claims wherein nⁿ _rF : i„s 18τ F.

28. A process according to claim 25 or claim 26 wherein ⁿF is ^l F and the further compound of formula (III) is any one of the following compounds:

[ rl¹8⁸F]Fallypride,

and

29. A process according to any one of claims 1 to 6 wherein "F is ¹⁸F, R² is H and R¹ is a group of formula (VIII)

[ rl¹8⁸F]FECNT or

30. A process according to any one of claims 1 to 6 wherein ⁿF is F, R is H and

R¹ is a group of formula (VII)

31. A process according to any one of claims 1 to 6 wherein ⁿF is ¹⁸F, and wherein R¹, R² and the C(H) group to which R¹ and R² are both bonded together form a group of formula (XIV)

wherein the fluorine-labelled compound of formula (III) is

[ 1-1¹8⁸F]FCWAY.

32. A compound of formula (I)

wherein:

wherein Rf is a straight-chained or branched C_4-12 perfluoroalkyl group; and L is a single bond, -alk-, -arylene-, -alk-arylene-, alk-X-, -arylene-X-, -alk- arylene-X, -alk-X-arylene-, -alk-X-arylene-X-, -arylene-alk-, -arylene-X-alk-, -arylene-alk-X- or -arylene-X-alk-X-, wherein X is N(R"), O, S, C(O) or C(O)N(R") and wherein alk is unsubstituted or substituted C_1-10 alkylene which is optionally interrupted by N(R"), O, S, C(O), C(O)N(R") or arylene, wherein R" is C_1-6 alkyl or aryl.

33. A compound according to claim 32 wherein R¹, R² and the C(H) group to which R¹ and R² are bonded together form (i) a tracer moiety, (ii) a moiety which is a precursor to a tracer moiety, or (iii) a labelling agent moiety, which labelling agent moiety comprises a functional group suitable for attachment of the compound to a tracer moiety or to a precursor of a tracer moiety.

34. A compound according to claim 32 or claim 33 wherein R¹ and R² are as defined in claim 5.

35. A compound according to any one of claims 32 to 34 wherein L is methylene, ethylene or propylene and Rf is -(CF₂)₅CF₃, -(CF₂)₆CF₃ or -(CF₂)₇CF₃.

36. A compound according to any one of claims 32 to 35 or a process according to any one of claims 1 to 30 wherein the compound of formula (I) is a light fluorous compound.

37. A compound according to any one of claims 32 to 36 or a process according to any one of claims 1 to 6 wherein the compound of formula (I) is selected from any one of the following compounds:

38. A process for producing a compound of formula (I)

wherein:

wherein Rf is a straight-chained or branched C_4-12 perfluoroalkyl group; and L is a single bond, -alk-, -arylene-, -alk-arylene-, alk-X-, -arylene-X-, -alk- arylene-X, -alk-X-arylene-, -alk-X-arylene-X-, -arylene-alk-, -arylene-X-alk-,

-arylene-alk-X- or -arylene-X-alk-X-, wherein X is N(R"), O, S, C(O) or C(O)N(R") and wherein alk is unsubstituted or substituted C]_-I0 alkylene which is optionally interrupted by N(R"), O, S, C(O), C(O)N(R") or arylene, wherein R" is C_1-6 alkyl or aryl; which process comprises treating a compound of formula (FV)

R¹

C(H)-OH (IV)

39. A process according to claim 38 wherein R² is H and R¹ is -alk-C ≡€H, wherein -alk- is as defined in claim 38, and the process further comprises treating the compound of formula (I) thus produced with an azide of formula (XXXVII)

N₃-R³⁴ (XXXVII)

wherein R³⁴ is -alk-R³⁵, -alk-C(O)-R³⁵, -C(O)-R³⁵, a tracer moiety, or a moiety which is a precursor to a tracer moiety, wherein alk is as defined in claim 38 and R is unsubstituted or substituted C_1-20 alkyl, aryl, or a group which comprises a peptide or an amino acid residue, and thereby producing a further compound of formula (I) having the following formula:

40. A combination product comprising (a) a compound of formula (IV)

R¹

\

C(H)-OH (IV)

R^ wherein R¹, R² and the C(H) group to which R¹ and R² are bonded together form a moiety to be labelled with fluorine; and (b) a compound of formula (V)

-arylene-alk-X- or -arylene-X-alk-X-, wherein X is N(R"), O, S, C(O) or C(O)N(R") and wherein alk is unsubstituted or substituted Ci_-10 alkylene which is optionally interrupted by N(R"), O, S, C(O), C(O)N(R") or arylene, wherein R" is C_1-6 alkyl or aryl; and either y is 1 and X' is a halo group, or y is 2 and X' is O.

41. A process according to claim 38 or a combination product according to claim 40 wherein R¹ and R² in the compound of formula (FV) are as defined in claim 6.

42. A process according to claim 38 or claim 41 or a combination product according to claim 40 or claim 41 wherein the compound of formula (FV) is any one of the following compounds:

43. A process according to any one of claims 38, 41 and 42 or a combination product according to any one of claims 40, 41 and 42 wherein the compound of formula (V) is any one of the following compounds:

F F F F F F F F and F F F F F F