GB2496971A - Preparation of X-ray contrast agents - Google Patents

Abstract

Synthetic routes for preparation of a chemical compound containing two linked iodinated phenyl groups and in particular, novel syntheses of loforminol (5,5 -(2-hydroxypropane-1,3-diyl)bis(formylazanediyl)bis(N1,N3-bis(2,3-dihydroxypropyl)-2,4,6-triiodoisophthalamide)), a contrast agent useful in X-ray imaging. The starting material of the syntheses is 5- amino-2,4,6-triiodoisophthalic acid. 5-Formamido-2,4,6-triiodoisophthaloyl dichloride or 5-Formamido-2,4,6-triiodoisophthalic acid may be intermediates in the preparation. Also shown is 5-Formamido-2,4,6-triiodoisophthaloyl dichloride per se and a process for preparation of an X-ray contrast agent using 5-Formamido-2,4,6-triiodoisophthaloyl dichloride or 5-Formamido-2,4,6-triiodoisophthalic acid as starting material or as an intermediate.

Description

Preparation of x-ray contrast agents The present invention relates to alternative synthetic routes for preparation of a chemical compound containing two linked iodinated phenyl groups. More particularly the invention relates to novel syntheses of loforminol, a contrast agent useful in X-ray imaging.

For the last 50 years the field of X-ray contrast agents has been dominated by soluble iodine containing compounds. Commercial available contrast media containing iodinated contrast agents are usually classified as ionic monomers such as diatrizoate (marketed e.g. under the trade mark GastrografenTM), ionic dimers such as ioxaglate (marketed e.g. under the trade mark HexabrixTM), nonionic monomers such as iohexol (marketed e.g. under the trade mark OmnipaqueTM), iopamidol (marketed e.g. under the trade mark lsovueTM), iomeprol (marketed e.g. under the trade mark lomeronTM) and the non-ionic dimer iodixanol (marketed under the trade mark VisipaqueTM). The most widely used commercial non-ionic X-ray contrast agents such as those mentioned above are considered safe. Contrast media containing iodinated contrast agents are used in more than 20 millions of X-ray examinations annually in the USA and the number of adverse reactions is considered acceptable. However, since a contrast enhanced X-ray examination will require up to about 200 ml contrast media administered in a total dose, there is a continuous drive to provide improved contrast media.

The part of the patient population considered as high risk patients is increasing. To meet the need for continuous improvement of in vivo X-ray diagnostic agents for the entire patient population, there is a continuous drive in finding X-ray contrast agents that has improved properties, also with regards to contrast induced nephrotoxicity (CIN).

X-ray contrast media containing a chemical compound as the active pharmaceutical ingredient(s) having two triiodinated phenyl groups linked by a linking group are usually referred to as dimeric contrast agents or dimers. During the years a wide variety of iodinated diners have been proposed. Currently, one contrast medium having an iodinated non-ionic dimer as the active pharmaceutical ingredient is on the market, the product VisipaqueTM containing the compound iodixanol.

The following patent application and publications are directed to a novel dimeric contrast agent named loforminol: W02009/008734 of the applicant! and Chai et al. "Predicting cardiotoxicity propensity of the novel iodinated contrast medium GE-145: ventricular fibrillation during left coronary arteriography in pigs", Acta Radiol, 2010 and the publication of Wistrand, [.13., etal."GE-145, a new low-osmolar dimeric radiographic contrast medium", Acta Radiol, 2010. The publications show that the compound GE-145, now called loforminol, has improved properties, such as increased hydrophilicity and lower osmolality than iodixanol (Visipaque®).

loforminol is named Compound 1 herein and has the following structure: HO.L}i Compound 1: 5,5'-(2-hydroxypropane-1,3-diyl)bis(formylazanediyl)bis(N1,N3-bis(2, 3-dihydroxypropyl)-2,4,6-triiodoisophthalamide) The manufacture of non-ionic X-ray contrast media involves the production of the chemical drug, the active pharmaceutical ingredient (API), i.e. the contrast agent, followed by the formulation into the drug product, herein denoted the X-ray composition. W02009/008734 of the applicant provides a synthetic route for preparing loforminol. loforminol can e.g., as provided by the general preparation description and Example 1 of W02009/008734, be synthesized from 5-Amino-N,N'-bis-(2,3-dihydroxy-propyl)-2,4,6-triiodo-isophthalamide, which is commercially available. The preparation of 5-amino-N1,N3-bis(2,3-dihydroxypropyl)-2,4,6-triiodoisophthalamide is known from the synthesis of both iohexol and iodixanol and can be prepared from 5-nitroisophthalic acid for instance as described in W02006/01 6815. The free amino group of this isophthalamide compound is then -o -(1) --CA -I 703) 3 fl I r -fl C, CD 9 C C CD 0 CD S-a 0 CD 1' QCD ra 3 3) CD 0 N.) H -h 9 zi 0 0 -ra CD CD -. r r -CD 0 00 0 0

CD -. CA <0

CAOaa \-o 0 0 00 0 ( 0 CA >C

CA CD

-, V (0 __ a CD3--c a 0 ___ ___ Q( (14 -0 (i CD

CD -

Cl) -Co

CA

CDCD ZI ZI ZI

-o ---h CD 0 0 0 00 -0

-CA

o CD -t_z -%-_Z -Z - CD -ZI i I I 9 3 CD Cl) -, M C.') 3 -aC ZI 0 0 9 -I 3o o 0

CD I I 0 -h -

Cl) a w 0 a 0 a CD >< 3) C-V03) C a

CD

a - a 0) a CD Ni CD 5 z,-O a 0 CA (0 a CD gCDan o 9 -C

CD

CD -5.a -4 Cl) 0) a-3) 0 C (0 (0

CD

CD r

The applicant has found that loforminol can be synthesized by alternative syntheses from commercially available and relatively inexpensive starting materials.

In a first aspect the invention provides a process for preparation of loforminol from 5-amino-2,4,6-trUodoisophthalic acid.

The starting material 5-amino-2,4,6-triiodoisophthalic acid is herein named compound 5. This precursor compound is commercially available, e.g. from Sigma-AId rich. HO 0

I__ I

HO NH2

O I

Compound 5.

Alternatively, compound 5 can be prepared by hydrogenation of 5-nitroisophthalic acid, providing 5-aminoisophthalic acid, and subsequent iodination e.g. by iodine chloride, ICI.

Alternative synthetic routes from compound 5 to loforminol falling within the scope of the invention are shown in scheme 2. HO 0

HO NH2 07 HO1 Ci Ci H01u1 (7 NH i(''t NSO yry NH

OH

NH HO4N NOH O l0 0 I OHt0l 0 ic HOO 0,OH 2c13c/4c I I I I HO 81 OH

NN

01 0 10 P0 id

OH H

HO-LN o ci o o ci HO24NH

OHH I H OHH H OH

HO_LNtO OtN,LOH HOLNtO OHHII OH if OHHII OH 01 OH 10 OH OH 0 0 10 0 0 RAO Scheme 2.

Key intermediates in the process of the invention are compound 6 and compound 12, hence the invention provides a process for preparation of loforminol from 5- amino-2,4,6-triiodoisophthalic acid (5), wherein 5-Formamido-2,4,6-triiodoisophthalic acid (6) is an intermediate. The invention further provides such a process wherein 5-Formamido-2,4,6-trflodoisophthaloyl dichloride (12) is an intermediate.

In a first embodiment, the process of the invention includes the following sequential steps: 1 a. formylation of the amino function of 5-amino-2,4,6-trDodoisophthalic acid (5) providing 5-forrnamido-2,4,6-trhodoisophthalic acid (6); lb. dimerization by linking two molecules of (6) via a 2-hydroxypropane-1,3-diyl bridge providing 5,5'-((2-hydroxypropane-1 3-diyl)bis(formylazanediylflbis(2,4,6-triiodoisophthalic acid (7); 1 c. protection of the hydroxyl group of the 2-hydroxypropane-1,3-diyl bridge providing compound 8; ld. chlorination of the carboxylic acid functions of compound 8 to provide compound 9; 1 e. amidation reaction of the acyl chlorides of compound 9 to provide compound 10; lf. removal of the protecting group of the 2-hydroxypropane group of compound providing compound 1.

In step lc the hydroxyl group of 2-hydroxypropane bridge of compound 7 is protected by acylation. Suitable protecting groups include acyl groups such as acetyl and formyl, i.e. S of compound 8 is preferably selected from the group of hydrogen and methyl. The hydroxyl group is hence e.g. protected by reaction with a mixture of acetic anhydride and acetic acid, but other known protecting groups for the hydroxyl groups such as benzoyl (Bz), benzyl (Bn, Bnl), 3-Methoxyethoxymethyl ether (MEM), Dimethoxytrityl, [bis-(4-methoxyphenyl)phenylmethyl] (DMT), Methoxymethyl ether (MOM), Methoxytrityl [(4-methoxyphenyl)diphenylmethyl, MMT), p-Methoxybenzyl ether (PMB), Methylthiomethyl ether, Pivaloyl (Piv), Tetrahydropyranyl (THP), Trityl (triphenylmethyl, Tr) or Silyl ethers may also be used. When R is methyl compound 8 is 5,5'-2-acetoxypropane-1,3-diyl)bis(formylazanediyl))bis(2,4, 6-trhodoisophthalic acid (8) , chlorination of this provides 1,3-bis(N-(bis(chlorocarbony-2,4,6-trHodophenyl)formamido)propan-2-yl acetate (9), and amidation reaction of the acyl chlorides of compound 9 provides 1,3-bis((2,3-dihydroxypropyl)carbamoyl)2,4,6-triodophenyl)formamido) propan-2-yl acetate (10).

When R is hydrogen compound 8 is 5,5'-((2-(formyloxy)propane-1 3-diyl)bis(formylazanediyl))bis(2,4,6-trhodoisophthalic acid) (8), and chlorination of this provides compound 9 which is 1,3-bis(N-(bis(chlorocarbonyl)-2,4,6-triiodophenyl)formamido)propan-2-yI formate (9), and an amidation reaction of this provides compound 10 which is 1,3-bis2,3-dihydroxypropycarbamoy2,4,6-triodophenyformamido)propan-2-yI formate (10).

The steps may be combined, e.g. steps le and if may be performed in one step without any isolation of compound 10. In the case of 0-formyl protection, i.e. RH, the two last steps are always combined into one step, shown as ig in Scheme 2, without any isolation of compound 10.

In a second embodiment, the process of the invention includes the following sequential steps: 2a. Formylation of the amino function of 5-amino-2,4,6-trUodoisophthalic acid (5) providing 5-forrnamido-2,4,6-trhodoisophthalic acid (6); 2ft chlorination of the carboxylic acid functions of compound 6 providing 5-formamido-2,4,6-trDodoisophthaloyl dichloride (12); 2c. amidation reaction of the acyl chlorides of compound 12 providing N1, bis(2,3-dihydroxypropyl)-5-formamido-2,4,6-trioiodoisphtalamide (2); 2d. dimerization by linking two molecules of (2) via a 2-hydroxypropane bridge providing compound 1.

In a third embodiment, the process of the invention includes the following sequential steps: 3a. chlorination of the carboxylic acid functions of compound 5 to provide 5-amino-2,4,6-triiodoisophthaloyl dichloride (11); 3b. formylation of the amino function of compound 11 providing 5-formamido- 2,4,6-trhodoisophthaloyl dichloride (12); 3c. amidation reaction of the acyl chlorides of compound 12 providing NI, bis(2,3-dihydroxypropyl)-5-formamido-2,4,6-trioiodoisphtalamide (2); 3d. dimerization by linking two molecules of compound 2 via a 2-hydroxypropane bridge providing compound 1.

Compound 11 is commercially available, and as an alternative the synthetic route of this embodiment may start with compound 11.

In a fourth embodiment, the process of the invention includes the following sequential steps: 4a. chlorination of the carboxylic acid functions of compound 5 providing 5-Sulfinylamino-2,4,6-triiodoisophthaloyl dichloride (13); 4b.formylation of the sulfinylamino function of compound 13 providing 5-formamido-2,4,6-triiodoisophthaloyl dichloride (12); 4c. amidation reaction of the acyl chlorides of compound 12 providing N1, N3-bis(2,3-dihydroxypropyl)-5-formamido-2,4,6-trioiodoisphtalamide (2); 4d. dimerization by linking two molecules of (2) via a 2-hydroxypropane bridge providing compound 1.

In this route compound 12 is prepared from compound S via a sulfinyl derivative (13).

US2O1 1/0275850 describes this compound (13) and its preparation. Regarding step 4b the conversion of the substructure N-sulfinyl-aniline with formic acid to a formanilide has been described by W. T. Smith & G.G. King in Journal of Organic Chemistry, 1959, vol. 24, p. 976 and Cane & Libermann in Bulletin de Ia Societe Chimique de Fiance, 1933, vol. <4> 53, p. 294.

The foun synthetic routes have several steps in common.

In steps 1 a/2a and 3b of the four synthetic routes the free amino function of the iodinated phenyl group is formylated to prepare the corresponding formanilide group.

The formylation may be effected by any convenient method, e.g. by use of activated formic acid such as mixed anhydrides, which can be prepared by a variety of methods described in the literature. Preferably, a mixture of formic acid and acetic anhydride is used in this step. A convenient method of preparing mixed anhydrides is to add a carboxylic acid anhydride to an excess of formic acid under controlled temperature. It is also possible to make mixed anhydrides by addition of a carboxylic acid chloride to a solution of a formic acid salt. Formyl-mixed anhydrides may include acetyl, isobutyryl, pivaloyl, benzoyl etc. An important common step for the four routes is the chlorination, taking place in steps ld, 2b, 3a and 4a converting the carboxylic acid functions of the iodinated phenyl groups to acyl chlorides, i.e. to the reactive derivatives of the carboxylic acids. Thionyl chloride (SOd2), or alternatively phosphorus trichloride (PCI3) or phosphorus pentachloride (PCI5) or oxalyl chloride (C2C1202), may be used in these reactions to treat the carboxylic acids. Thionyl chloride is preferred and is a requirement for step 4a. The reactive acyl chloride moieties can then be converted into the hydrophilic side chains of the agent, i.e. to the -CONHCH2CHOHCH2OH moieties.

The synthetic route of the first embodiment differentiates over the syntheses of the other embodiments in that the dimerization takes place in an early step of the synthetic route. Step lb includes dimerization by linking two molecules of compound 6 via a 2-hydroxypropane-1,3-diyl bridge. Hence, in this embodiment the dimerization takes place before the hydrophilic side chains of the agent, i.e. the -CONHCH2CHOHCH2OH moieties, are generated. The dimerisation steps, for all the syntheses, including steps lb or 2d/3d14d may be carried out as described in European patent 108638 and WO 98123296, for example using epichlorohydrin, 1,3-dichloro-2-hydroxypropane or 1,3-dibromo-2-hydroxypropane as the dimerisation agent. The synthetic routes covered by the present document may equally well be used in the synthesis of similar compounds having different bridges than 2-hydroxypropane-1,3-diyl. Suitable bridges and suggested agents for the dimerization are described in W02009/008734 of the Applicant and these are incorporated herein by reference. E.g. the bridge between the amide functions could comprise a straight 03 to 08 alkylene chain optionally substituted by one to six hydroxyl groups, and the agent used in the dimerization must be chosen accordingly.

The dimerization reaction of steps 2d/3d/4d may be carried out in a non-aqueous solvent such as a 01-6-alcohol, preferably 2-methoxyethanol and/or methanol.

Dimerisation in pure water or mixtures of water and one or more alcohols (e.g. Cl- 6-alkanols) or in a solvent comprising 1-metoxy-2-propanol is also possible. Step lb is preferably carried out in pure water but may be carried out in mixtures of water and one or more alcohols (e.g. C1-6-alkanols) or in mixtures of water and 2-methoxyethanol or in mixtures of water and 1-metoxy-2-propanol.

The dimerisation is preferably effected in the presence of an acid binding agent, for example an organic or inorganic base preferably in aqueous or alcoholic medium or mixtures thereof such as water and/or an alkanol or glycol; an alkali metal alkoxide such as sodium metoxide or an alkali metal hydroxide such as sodium and potassium hydroxide may be used as base.

In steps le and 2c/3c the acyl chloride groups of the iodinated phenyls are substituted with the hydrophilic side chains. This is preferably effected by reacting the acyl chlorides with 3-aminopropane-1 2-dial. In the synthesis of the first embodiment, the hydroxyl group of the 2-hydroxypropane-l,3-diyt bridge should be protected, i.e. by acylation (step lc), prior to such substitution reaction. The synthetic routes covered by the present document may equally well be used in the synthesis of similar compounds having different hydrophilic side chains than -CONHCH2CHOHCH2OH. Accordingly, the syntheses may be used in preparation of compounds comprising any non-ionizing groups conventionally used to enhance water solubility. Such groups are denoted R2 in W02009/008734, and such groups are incorporated herein.

Compound 1 as prepared by the claimed process comprises optical active isomers and will exist in several isomeric forms due to chiral carbon atoms. In addition, the compounds exhibit exo/endo isomerism due to the restricted rotation of the N-CO bond in the formyl function caused by the proximity of the bulk iodine atom. Both preparation of enantiornerically pure products as well as mixtures of optical isomers are encompassed by the process of the invention.

The compounds prepared, such as compound 1, may be purified in any convenient manner, e.g. by preparative chromatography, by recrystallization or ultra/nano-filtration.

The compounds prepared according to the invention may be used as contrast agents and may be formulated with conventional carriers and excipients to produce diagnostic contrast media. Thus viewed from a further aspect the invention provides a diagnostic composition comprising loforminol prepared according to the process of the invention, together with at least one physiologically tolerable carrier or excipient, e.g. in aqueous solution for injection optionally together with added plasma ions or dissolved oxygen. The contrast agent composition of the invention may be in a ready to use concentration or may be a concentrate form for dilution prior to administration. Hence, the invention further embraces use of loforminol prepared according to the process of preparation, and a diagnostic composition containing such, in X-ray contrast examinations.

In a further aspect, the invention provides novel compounds. In the synthetic routes of the second and third embodiments of the first aspect, the intermediate 5-formamido-2,4,6-trUodoisophthaloyl dichloride (12) is prepared. This novel compound may optionally be isolated, and may also be used in the preparation of other x-ray contrast agents than loforminol, also having a formanitide substructure.

Accordingly, the invention provides a process for preparation of an x-ray contrast agent including the use of 5-Formamido-2,4,6-trUodoisophthaloyl dichloride (12) as starting material or as an intermediate. Likewise, the invention provides a process for preparation of an x-ray contrast agent including the use of 5-Formamido-2,4,6-triiodoisophthalic acid (6) as starting material or as an intermediate.

The invention is illustrated with reference to the following non-limiting examples.

Examples

Example 1: Preparation of 5-Formamido-2,4,6-triiodoisophthalic acid (6)

I I

HO 0 I

Formation of acetic formic anhydride: A 500m1 reactor with cooling jacket, internal thermometer, mechanic stirrer is filled with formic acid (270 ml, 7,15 mol, 40 eq.) and cooled to 8°C. Slowly acetic acid anhydride (84,5 ml, 894 mmol, 5 eq.) is added keeping the inner temperature at <15°C. The mixture is kept at 15°C for 4h. It contains acetic formic anhydride and formic acid anhydride.

N-Formylation (alternative 1): 5-Amino-2,4,6-triiodoisophthalic acid (5) (1 OOg, 179 mmol, 1 eq., fine powder) is added to the mixture of acetic formic anhydride and stirred at 15-23°C for 2-3 days. The mixture is analysed for residual Ar-NH2 by UV, HPLC or NMR (1H-NMR 400MHz DMSO-d66 5,58 Ar-NH2). In case of iesidual Ar- NH2 more acetic formic anhydride solution is added keeping the temperature at 15- 23°C for 1-3 days. The reaction is quenched by adding water (97 ml, 5,36 mol, 30 eq.) and the precipitated product is filtered off and washed with water. The filter cake is dried in vacuum.

N-Formylation (alternative 2): A solution of 5-Amino-2,4,6-triiodoisophthalic acid (5) (100g. 179 mmol, 1 eq.) in DMF (100 ml, 1,29 mol, 7.2 eq.) is added to the mixture of acetic formic anhydride and stirred at 15-23°C for 1-3 days. The mixture is analysed for residual Ar-NH2 by UV, HPLC or NMR (H-NMR 400MHz DMSO-d65 5,58 Ar-NH2). In case of residual Ar-NH2 more acetic formic anhydride solution is added keeping the temperature at 15-23°C for 1-3 days. The reaction is quenched by adding water (32 ml, 1,78 mol, 10 eq.) and the product mixture is evaporated to dryness under high vacuum.

The product is analysed by HPLC/MS: Exact Mass: 586,72; Molecular Weight: mlz: 586,72 (100,0%), 587,73(10,0%), 588,73(1,5%) Chemical Formula: C9H413N05 Elemental Analysis: C 18,42; H 0,69; I 64,87; N 2,39; 0 13,63 1H-NMR 400MHz DMSO-d65 10,25 9,85 9,83 Ar-NH-CHO Example 2: Preparation of 5,5'-((2-hydroxypropane-1,3-diyI)bis(formylazanediyl))bis(2,4, 6-triiodoisophthalic acid) (7) HO 0 0 OH

I I I I

HO NN OH

0 I OH I 0 Dimerization (alternative 1): A 500m1 reactor with cooling jacket, internal thermometer, mechanic stirrer is filled with water (250 ml, 13,8 mol, 82 eq.), sodium hydroxide (18,4 g, 468 mmol, 2,75 eq.) and cooled to 10°C. 5-Formamido-2,4,6-trDodoisophthalic acid (6)(lOOg, 170 mmol, 1 eq.) is added at a speed keeping the temperature below 15°C. Epichlorohydrin (6,81 ml, 86,9 mmol, 0,51 eq.) is added and the reaction mixture stirred for 16-24h at 10°C. The mixture is analysed by HPLC or NMR. If necessary more epichlorohydrin is added and the reaction continues at 10°C for 1-3 days. The reaction is quenched by adding diluted sulphuric acid unto pH=0 keeping the inner temperature below 15°C. The precipitated product is filtered off and washed with water. The filter cake is dried in vacuum and stored cold protected against light.

Dimerization (alternative 2): A 500m1 reactor with cooling jacket, internal thermometer, mechanic stirrer, internal pH-electrode attached to a pH-stat is filled with water (250 ml. 13,8 mol, 82 eq.) and cooled to 10°C. 5-Formamido-2,4,6-triiodoisophthalic acid (6) (1 OOg, 170 mmol, 1 eq.) is added and the pH adjusted to 11,5 at 10°C. Epichlorohydrin (6,81 ml, 86,9 mmol, 0,51 eq.)is added and the reaction mixture stirred for 16-24h at 10°C. The mixture is analysed by HPLC or NMR. If necessary more Epichlorohydrin is added and the reaction may continue at 10°C for 1-3 days. The reaction is quenched by adjusting the pH toO keeping the inner temperature below 15°C. The precipitated product is filtered off and washed with water. The filter cake is dried in vacuum and stored cold protected against light.

The product is analysed by HPLC/MS: Exact Mass: 1229,47; Molecular Weight: m/z: 1229,47(100,0%), 1230,47(23,5%), 1231,48 (4,8%) Chemical Formula: C21H1216N2011 Elemental Analysis: C 20,51; H 0,98; I 61,92; N 2,28; 0 14,31 Example 3: Preparation of 5,5'-((2-acetoxypropane-1,3-diyl)bis(formylazanediyl))bis(2,4, 6-triiodoisophthalic acid) (8) with R = Methyl

I -I I I HomOH

0-Acetylation: A 500m1 reactor with jacket, reflux condenser, internal thermometer, mechanic stirrer is filled with acetic acid (21 ml, 366 mmol, Seq.), acetic anhydride (108 ml, 1,142 mol, 15.6 eq.), 5,5'-((2-hydroxypropane-1,3-diyl)bis(formylazanediyl))bis(2,4, 6-triiodoisophthalic acid) (7) (909,73,1 mmol, 1 eq.) and stirred for 15 mm at 23°C. Acetyl chloride (5,2 ml, 73,1 mmol, 1 eq.) is added and the mixture heated to 60-70°C for 14-24h. In order to precipitate the product acetic acid (141 ml, 2,46 mol, 33,7 eq.) is added at 60-70°C and stirred for 1-3h.

The reaction mixture is cooled to 15-20°C and filtered. The filter cake is washed with acetic acid (54 ml) and n-butyl acetate (54 ml), dried in vacuum and stored at ambient temperature protected against light.

The product is analysed by HPLC/MS: Exact Mass: 1271,48; Molecular Weight: 127 1,79 mfz: 1271,48 (1 00,0%). 1272,48 (25,6%), 1273,49(5,6%) Chemical Formula: C23H1416N2012 Elemental Analysis: C 21,72; H 1,11; I 59,87; N 2,20; 0 15,10 Example 4: Preparation of 1,3-bis(N-(3,5-bis(chlorocarbonyl)-2,4,6-triiodophenyl)formamido) propan-2-yl acetate (9) with R = Methyl CI 0 0 CI

I I I I

cia ilL Acid chlorination: A 500m1 reactor with jacket, reflux condenser, bubble counter connected to a scrubber, internal thermometer, mechanic stirrer is filled with n-butyl acetate (160 ml, 1.21 rnol, 19,3 eq.), 5,5'-((2-acetoxypropane-1,3-diyl)bis(formylazanediyl))bis(2,4, 6-trüodoisophthalic acid) (8) with R = Methyl (80 g, 62,9 mmol, 1 eq.), dimethyl formamide (0,242 ml, 3,15 mmol, 0,05 eq.) and thionyl chloride (77,8 ml, 1,07 mol, 17 eq.) at 15-23°C. Under stirring the mixture is heated to 60-80°C keeping the gas evolution of SO2 and HCI under control. The reaction is complete when the gas evolution stops. The reaction mixture is cooled to 15-20°C and filtered. The filter cake is washed with butyl acetate (46 ml), dried in vacuum and stored at ambient temperature protected against light and moisture.

The product is analysed by MS: Exact Mass: 1343,35; Molecular Weight: 1345,57 mlz: 1345,34 (100,0%), 1343,35 (78,2%), 1347,34 (48,1%), 1346,35 (25,6%), 1344,35(19,8%), 1348,34 (12,4%), 1349,34(11,1%), 1347,35(4,7%), 1345,35 (3.8%). 1350,34 (2,6%), 1349.35(1,5%) Chemical Formula: C23H10C1416N208 Elemental Analysis: C 20.53; H 0.75; Cl 10,54; I 56.59: N 2,08; 0 9,51 Example 5: Preparation of I,3-bis(N-(3,5-bis((2,3-dihydroxypropyl)carbamoyl)- 2,4,6-triiodophenyl)formamido)propan-2-yl acetate (10) with R = Methyl HO o OH

II II

(OH O "NO I HO OH Amidation: At 10°C a reactor with jacket, internal thermometer, mechanic stirrer is filled with THE (80 ml, 986 mmol, 16,6 eq.), Triethylamine (37,2 ml, 267 mmol, 4,5 eq.), water (40 ml, 2,22 mol, 37 eq.), fine crushed 1,3-bis(N-(3,5-bis(chlorocarbonyl)-2,4,6-triiodophenyl)formamido) propan-2-yl acetate (9) with S = Methyl (80 g, 59,4 mmol, 1 eq.), 3-Amino-propane-i,2-diol (35,2 g, 386 mmol, 6,5 eq.) and stirred for 24h. The reaction mixture forms 2 phases. The upper THF phase is removed and the lower phase transferred to an evaporation flask. Volatile components like THE and NEt3 were removed by partial evaporation at 50 mbar/22°C. The product solution is ready for use in the deacetylation step.

The product is analysed by HPLC/MS: Exact Mass: 1563,69; Molecular Weight: mlz: 1563,69(100,0%), 1564,70 (38,9%), 1565,70(10,7%), 1566,70 (2,3%), 1564,69 (2,2%) Chemical Formula: C35H4215N6016 Elemental Analysis: C 26,88; H 2,71; I 48,68; N 5,37; 0 16,37 Example 6: Preparation of loforminol; AH1 13111; 5,5'-((2-hydroxypropane-1,3- diyl)bis(formylazanediyl))bis(N1,N3-bis(2,3-dihydroxypropyl)-2,4, 6-triiodoisophthalamide) (1)

HO OOH

II

HNCN

bOH 0 I OH I 0 HO

OH OH

Deacetylation (alternative 1): To the solution of (10) from exampleS a solution of potassium hydroxide (20 g, 356 mmol, 6 eq.tcompound (9) with S = Methyl) in methanol (20 ml) and water (60 ml) is added and stirred at 22°C. The reaction is monitored by HPLC and stopped after complete deacetylation. The product solution is diluted with water, neutralized to pH 7 and purified by nanofiltration. The retentate is filtered or evaporated to dryness. The product is dried in vacuum and stored at ambient temperature protected against light.

Deacetylation (alternative 2): A reactor with cooling jacket, internal thermometer, mechanic stirrer, internal pH-electrode attached to a pH-stat is filled with water (100 ml) and cooled to 10°C. The solution of (10) from example 5 is added and the pH-stat set to pH 12,5 at 10°C. The reaction is monitored by HPLC and stopped after complete deacetylation. The product solution is diluted with water, neutralized to pH 7 and purified by nanofiltration. The retentate is filtered or evaporated to dryness.

The product is dried in vacuum and stored at ambient temperature protected against light.

The product is analysed by HPLC/MS: Exact Mass: 1521,68; Molecular Weight: m/z: 1521,68(100,0%), 1522,69 (36,7%), 1523,69(9,6%), 1522,68(2,2%), 1524,69 (2,0%) Chemical Formula: C33H4016N6015 Elemental Analysis: C 26,04; H 2,65; I 50,02; N 5,52; 0 15,77 Example 7: Preparation of 5,5'-((2-(formyloxy)propane-1.3-diyl)bis(formylazanediyl))bis(2,4, 6-triiodoisophthalic acid) (5) with R = H HO 0 0 OH

I I I -I

HO NN OH

0 I I 0 Formation of acetic formic anhydride: A 500m1 reactor with cooling jacket, internal thermometer, mechanic stirrer is filled with formic acid (155 ml, 4,1 mol. 56 eq.) and cooled to 8°C. Slowly acetic acid anhydride (48,4 ml, 512 mmol, 7 eq.) is added keeping the inner temperature at <15°C. The mixture is kept at 15°C for 4h. It contains acetic formic anhydride and formic acid anhydride. Be aware of carbon monoxide in the reactor head space.

0-Formylation (alternative 1): 5,5'-((2-hydroxypropane-1.3-diyl)bis(formylazanediyl))bis(2,4, 6-trhodoisophthalic acid) (7) (90g, 73,2 mmol, 1 eq., fine powder) is added to the mixture of acetic formic anhydride and stirred at 15- 23°C for 2-3 days. The mixture is analysed for residual starting material by HPLC or NMR. In case of residual starting material more acetic formic anhydride solution is added keeping the temperature at 15-23°C for 1-3 days. The reaction is quenched by adding water (18 ml, 1 mol, 14 eq.) and the precipitated product is filtered off and washed with water. The filter cake is dried in vacuum and stored cold protected against light.

0-Formylation (alternative 2): A solution of 5,5'-((2-hydroxypropane-1 3-diyl)bis(formylazanediyl))bis(2,4,6-trhodoisophthalic acid) (7) (90g. 73,2 mmol, 1 eq., fine powder) in dimethyl formamide (90 ml, 1,16 mol, 16 eq.) is added to the mixture of acetic formic anhydride and stirred at 15-23°C for 2-3 days. The mixture is analysed for residual starting material by HPLC or NMR. In case of residual starting material more acetic formic anhydride solution is added keeping the temperature at 15-23°C for 1-3 days. The reaction is quenched by adding water (18 ml, 1 mcI, 14 eq.) and evaporated to dryness under high vacuum at 23-30°C. The residue is dried in vacuum and stored cold protected against light.

The product is analysed by HPLC/MS: Exact Mass: 1257,47; Molecular Weight: m/z: 1257,47 (1 00,0%), 1258,47 (24,4%), 1259,47 (5,5%) Chemical Formula: C22H1215N2012 Elemental Analysis: C 21,01; H 0,96;160,54; N 2,23; 0 15,26 Example 8: Preparation of I,3-bis(N-(3,5-bis(chlorocarbonyl)-2,4,6-triiodophenyl)formamido) propan-2-yl formate (9) with R = H Ci 0 o ci

I I I -

ci NN ci I I 0 Acid chlorination: A 500m1 reactor with jacket, reflux condenser, bubble counter connected to a scrubber, internal thermometer, mechanic stirrer is tilled with n-butyl acetate (160 ml, 1,21 rnol, 19,1 eq.), 5,5'-((2-(formyloxy)propane-1,3-diyl)bis(formylazanediyl))bis(2,4, 6-triiodoisophthalic acid) (8) with R = H (80 g, 63,6 mmol, 1 eq.), dimethyl formamide (0,245 ml, 3,18 mmol, 0,05 eq.) and thionyl chloride (78,6 ml, 1,08 mcI, 17 eq.) at 15-23°C. Under stirring the mixture is heated to 60-80°C keeping the gas evolution of SO2 and HCI under control. The reaction is complete when the gas evolution stops. The reaction mixture is cooled to 15-20°C and filtered. The filter cake is washed with butyl acetate (46 ml), dried in vacuum and stored at ambient temperature protected against light and moisture.

The product is analysed by MS: Exact Mass: 1329,33; Molecular Weight: 1331,55 mlz: 1331,33 (1 00,0%), 1329,33 (77,1%), 1333,32(47,3%), 1332,33 (23,9%), 1330,33(19,2%), 1334,33 (11,9%), 1335,32(10,2%), 1333,33 (4,5%), 1336,32 (2,5%), 1331,34 (2,2%), 1335,33(2,1%) Chemical Formula: C22H3C1416NJ208 Elemental Analysis: C 19,84; H 0,61; Cl 10,65; 157,18; N 2,10; 09,61 Example 9: Preparation of loforminol; AH1 13111; 5,5'-((2-hydroxypropane-1,3- diyl)bis(formylazanediyl))bis(N1, N3-bis(2,3-dihydroxypropyl)-2,4,6-triiodoisophthalamide) (1)

HOHO OH

II II

OH I OH 0 HO

OH OH

Amidation and de-0-formylation: At 10°C a reactor with jacket, internal thermometer, mechanic stirrer is filled with THF (88 ml, 1,08 mol, 18 eq.), Triethylamine (46 ml, 331 mmcl, 5,5 eq.), water (48 ml, 2,66 mol, 44 eq.), fine crushed 1,3-bis(N-(3,5-bis(chlorocarbonyl)-2,4,6-triiodophenyl)formamido) propan-2-yl formate (9) with R = H (809,60,18 mmol, 1 eq.), 3-Amino-propane-i,2-diol (38,49,421 mmol, 7 eq.) and stirred for 24h. The reaction mixture forms 2 phases. The upper THE phase is removed and the lower phase transferred to an evaporation flask. Volatile components like THE and NEt3 were removed by partial evaporation at 50 mbar/22°C. The product solution is diluted with water, neutralized to pH 7 and purified by nanofiltration. The retentate is filtered or evaporated to dryness. The product is dried in vacuum and stored at ambient temperature protected against light.

The product is analysed by HPLC/MS: Exact Mass: 1521,68; Molecular Weight: mfz: 1521,68(100,0%), 1522,69 (36,7%), 1523,69(9,6%), 1522,68 (2,2%), 1524,69 (2,0%) Chemical Formula: C33H4015N5015 Elemental Analysis: C 26,04; H 2,65; I 50,02; N 5,52; 0 15,77 Example ID: Preparation of 5-formamido-2,4,6-triiodoisophthaloyl dichloride (12) Cl N H 0 I Acid chlorination (alternative 1): A 500m1 reactor with jacket, reflux condenser, bubble counter connected to a scrubber, internal thermometer, mechanic stirrer is filled with n-butyl acetate (200 ml, 1,51 mol, 8,9 eq.), 5-Formamido-2,4,6-triiodoisophthalic acid (6) (1009, 170,4 mmol, 1 eq.), dimethyl formamide (0,394 ml, 5,11 mmol, 0,03 eq.) and thionyl chloride (99,1 ml, 1,36 mol, 8 eq.) at 15-23°C.

Under stirring the mixture is heated to 60-80°C keeping the gas evolution of SO2 and HCI under control. The reaction is complete when the gas evolution stops. The reaction mixture is cooled to 15-20°C and filtered. The filter cake is washed with butyl acetate (60 ml), dried in vacuum and stored at ambient temperature protected against light and moisture.

Acid chlorination (alternative 2): A 500m1 reactor with jacket, reflux condenser, bubble counter connected to a scrubber, internal thermometer, mechanic stirrer is filled with thionyl chloride (198,2 ml, 2,72 mol, 16 eq.), 5-Formamido-2,4,6-triiodoisophthalic acid (6) (1009, 170,4 mmol, 1 eq.) and dimethyl formamide (0,394 ml, 5,11 mmol, 0,03 eq.)at 15-23°C. Under stirring the mixture is heated to 60-80°C keeping the gas evolution of SO2 and HCI under control. The reaction is complete when the gas evolution stops. The reaction mixture is cooled to 15-20°C and evaporated to dryness at 50°C/20 mbar. In order to reduce residual thionyl chloride the residue is suspendend in ethyl acetate (100 ml, 1,02 mol, 6 eq.) at 50°C for lh and evaporated to dryness at 50°C/20 mbar. The product is stored at ambient temperature protected against light and moisture.

Acid chlorination (alternative 3): Compound 13 is prepared from compound 5 according to US2O1 1/0275850A1 or EP2230227 Al. The starting material containing traces of residual thionyl chloride is suitable for the following procedure.

A reactor with jacket, reflux condenser, bubble counter connected to a scrubber, internal thermometer, mechanic stirrer is filled with n-butyl formate (161 ml, 1,40 mol, 9 eq.), 5-Sulfinylamino-2,4,6-triiodoisophthaloyl dichloride (13) (100 g, 155,8 mmol, 1 eq.) and formic acid (23,5 mI, 623 mmol, 4 eq.)at 15-23°C. Under stirring the mixture is slowly heated to 50-90°C keeping the gas evolution of S02 under control.

The reaction is complete when the gas evolution stops. The reaction mixture is cooled to 15-20°C and filtered. The filter cake is washed with butyl formate (60 ml), dried in vacuum and stored at ambient temperature protected against light and moisture.

The product is analysed by MS: Exact Mass: 622,65; Molecular Weight: 623,74 mlz: 622,65(100,0%), 624,65(64,0%), 626,65(10,2%), 623,66 (9,9%), 625,65 (6,5%), 624,66(1,1%), 627,65(1,0%) Chemical Formula: C9H2C1213N03 Elemental Analysis: C 17,33; H 0,32; Cl 11,37; 161,04; N 2,25; 07,70 1H-NMR 400MHz DMSO-d66 10,28 Ar-NH-CHO Example 11: Preparation of N1, N3-bis(2,3-dihydroxypropyl)-5-formamido-2,4,6-triiodoisophthalamide (2)

OH

H

HO N 0

OH I

HO 0 I

Amidation (alternative 1): At 10°C a reactor with jacket, internal thermometer, mechanic stirrer is filled with THF (100 ml, 1,23 mcI, 7,7 eq.), Triethylamine(55,8 ml, 401 mmol, 2,5 eq.), water (50 ml, 2,77 mol, 17 eq.), fine crushed 5-formamido-2,4,6- triiodoisophthaloyl dichloride (12) (1009, 160,6 mmcl, 1 eq.), 3-Amino-propane-i 2-diol (65,8 g, 722 mmol, 4,5 eq.) and stirred for 24h. The reaction mixture formes 2 phases. The upper THF phase is removed and the lower phase transferred to an evaporation flask. Volatile components like THF and NEt3 were removed by partial evaporation at 50 mbai-/22°C. The product solution is diluted with water, neutralized to pH 7 and purified by nanofiltration. The retentate is filtered or evaporated to dryness. The product is dried in vacuum and stored at ambient temperature protected against light.

Amidation (alternative 2): At 23°C a reactor with jacket, internal thermometer, mechanic stirrer is filled with Dimethyl formamide (100 ml, 1,29 mol, 8,1 eq.), Triethylamine (67 ml, 481 mmol, 3 eq.), fine crushed 5-formamido-2,4,6- triiodoisophthaloyl dichloride (1 2) (1009, 160,6 mmol, 1 eq.) and 3-Amino-propane- 1,2-diol (58,59,642 mmol, 4 eq.). The reaction mixture is stirred for 18h at 60°C.

The mixture is evaporated under vacuum 1 mbar/50°C. The residue is diluted with water, neutralized to pH 7 and purified by nanofiltration. The retentate is filtered or evaporated to dryness. The product is dried in vacuum and stored at ambient temperature protected against light.

The product is analysed by HFLC/MS: Exact Mass: 732,83; Molecular Weight: m/z: 732,83 (100,0%), 733,83(16,7%), 734,83(2,9%), 733,82(1,1%) Chemical Formula: C15H1513N307 Elemental Analysis: C 24,58; H 2,48; I 51,94; N 5,73; 0 15,28 Example 12: Preparation of 5-formamido-2,4,6-triiodoisophthaloyl dichloride (12) Cl N H 0 I N-formylation (alternative 1): A 500m1 reactor with cooling jacket, internal thermometer, mechanic stirrer is tilled with formic acid (253 ml, 6,71 mol, 40 eq.) and cooled to 8°C. Slowly acetic acid anhydride (79,4 ml, 839 mmol, 5 eq.) is added keeping the inner temperature at <15°C. The mixture is kept at 15°C for 4h. It contains acetic formic anhydride and formic acid anhydride. Be aware of carbon monoxide in the reactor head space. 5-amino-2,4,6-triiodoisophthaloyl dichloride (11)(lOOg, 167,8 mmol, 1 eq., fine powder) is added to the mixture of acetic formic anhydride and stirred at 15-23°C for 1-3 days. The mixture is analysed for residual Ar-NH2 by UV, HPLC or NMR (H-NMR 400MHz DMSO-d5O 5,72 Ar-NH2). In case of residual Ar-NH2 more acetic formic anhydride solution is added keeping the temperature at 15-23°C for 1-3 days. The reaction is quenched by adding water (30 ml, 1,67 mol, 10 eq.) and the precipitated product is filtered off and washed with Ethyl acetate (60 ml). The filter cake is dried in vacuum and the product is stored at ambient temperature protected against light and moisture.

N-formylation (alternative 2): A SOOml reactor with cooling jacket, internal thermometer, mechanic stirrer is filled with formic acid (253 ml, 6,71 mol, 40 eq.) at 15°C and 5-amino-2,4,6-triiodoisophthaloyl dichloride (11) (bOg, 167,8 mmol, 1 eq., fine powder). Slowly acetic acid anhydride (79,4 ml, 839 mmol, 5 eq.) is added keeping the inner temperature at 15-23°C. Be aware of carbon monoxide in the reactor head space. The mixture is stirred at 15-23°C for 1-3 days and is analysed for residual Ar-NH2 by UV, HPLC or NMR (1H-NMR 400MHz DMSO-d66 5,72 Ar-NH2). In case of residual Ar-NH2 more acetic anhydride is added keeping the temperature at 15-23°C for 1-3 days. The reaction is quenched by adding water (30 ml, 1,67 mol, 10 eq.) and the precipitated product is filtered off and washed with Ethyl acetate (60 ml). The filter cake is dried in vacuum and the product is stored at ambient temperature protected against light and moisture.

The product is analysed by MS: Exact Mass: 622,65; Molecular Weight: 623,74 mlz: 622,65(100,0%), 624,65(64,0%), 626,65(10,2%), 623,66 (9,9%), 625,65 (6,5%), 624,66(1,1%), 627,65(1,0%) Chemical Formula: C9H2C1213N03 Elemental Analysis: C 17,33; H 0,32; Cl 11,37; 161,04; N 2,25; 07,70 1H-NMR 400MHz DMSO-d5o 10,28 Ar-NH-CHO

Claims (1)

1. <claim-text>Claims 1. A process for preparation of loforminol starting from 5-amino-2,4,6-triiodoisophthalic acid (5).</claim-text> <claim-text>2. A process as claimed in claim 1 comprising a step of chlorination, converting carboxylic acid functions of the iodinated phenyl groups of 5-amino-2,4,6-trüodoisophthalic acid (5), or of a later intermediate, to acyl chlorides.</claim-text> <claim-text>3. A process as claimed in claim 1 or2 wherein 5-Formamido-2,4,6-triiodoisophthalic acid (6) is an intermediate.</claim-text> <claim-text>4. A process as claimed in any of claims 1 to 3 wherein 5-Formamido-2,4.6-triiodoisophthaloyl dichloride (12) is an intermediate.</claim-text> <claim-text>5. A process as claimed in any of claims 1 to 3 comprising the steps.la. formylation of the amino function of 5-amino-2,4,6-triiodoisophthalic acid (5) providing 5-formamido-2,4,6-trUodoisophthalic acid (6); lb. dimerization by linking two molecules of (6) via a 2-hydroxypropane-1 3- diyl bridge providing 5,5'-((2-hydroxypropane-l 3-diyl)bis(formylazanediyl))bis(2,4,6-triiodoisophthalic acid (7); lc. protection of the hydroxyl group ofthe2-hydroxypropane-1,3-diyl bridge providing compound 8; 1 d. chlorination of the carboxylic acid functions of compound 8 to provide compound 9; 1 e. amidation reaction of the acyl chlorides of compound 9 to provide compound 10; if. removal of the protecting group of the 2-hydroxypropane-1,3-diyl group of compound 10 providing loforminol.</claim-text> <claim-text>6. A process as claimed in any of claims 1 to 4 comprising the steps 2a. Formylation of the amino function of 5-amino-2,4,6-triiodoisophthalic acid (5) providing 5-formamido-2,4,6-triiodoisophthalic acid (6); 2b. chlorination of the carboxylic acid functions of compound 6 providing 5-formamido-2,4,6-trUodoisophthaloyl dichloride (12); 2c. amidation reaction of the acyl chlorides of compound 12 providing N1, N3-bis(2,3-dihydroxypropyl)-5-formamido-2,4,6-trioiodoisphtalamide (2): 2d. dimerization by linking two molecules of (2) via a 2-hydroxypropane-1 3-diyl bridge providing loforminol.</claim-text> <claim-text>7. A process as claimed in claims 1 012 comprising the steps 3a. chlorination of the carboxylic acid functions of compound 5 to provide 5-amino-2,4,6-trDodoisophthaloyl dichloride (11); 3b. formylation of the amino function of compound 11 providing 5-formamido- 2,4,6-trUodoisophthaloyl dichloride (12); 3c. amidation reaction of the acyl chlorides of compound 12 providing N1, N3-bis(2,3-dihydroxypropyl)-5-formamido-2,4,6-trioiodoisphtalamide (2); 3d. dimerization by linking two molecules of compound 2 via a 2-hydroxypropane-1,3-diyl bridge providing ioforminol.</claim-text> <claim-text>8. A process as claimed in claim 1 or 2 comprising the steps 4a. chlorination of the carboxylic acid functions of compound 5 providing 5-Sulfinylamino-2,4,6-triiodoisophthaloyl dichloride (13); 4b. formylation of the sulfinylamino function of compound 13 providing 5-formamido-2,4,6-triiodoisophthaloyl dichloride (12): 4c. amidation reaction of the acyl chlorides of compound 12 providing N1, tt-bis(2,3-dihydroxypropyl)-5-formamido-2,4,6-trioiodoisphtalamide (2); 4d. dimerization by linking two molecules of (2) via a 2-hydroxypropane-1 3-diyl bridge providing compound 1.</claim-text> <claim-text>9. A process as claimed in any of claims 1 to 8 wherein any two subsequent steps are combined without isolation of the intermediate.</claim-text> <claim-text>10. loforminol prepared by the process of preparation according to any of claims ito 9.</claim-text> <claim-text>11. A composition comprising loforminol prepared according to the process of preparation according to any of the claims 1 to 9.</claim-text> <claim-text>12. 5-Formamido-2,4,6-triiodoisophthaloyl dichloride (12).</claim-text> <claim-text>13. A process for preparation of an x-ray contrast agent including the use of 5-Formamido-2,4,6-triiodoisophthaloyl dichloride (12) as starting material or as an intermediate.</claim-text> <claim-text>14. A process for preparation of an x-ray contrast agent including the use of 5-Formamido-2,4,6-triiodoisophthalic acid (6) as starting material or as an intermediate.</claim-text>