NZ714831B2 - Diazacarbazole derivatives as tau-pet-ligands - Google Patents
Diazacarbazole derivatives as tau-pet-ligands Download PDFInfo
- Publication number
- NZ714831B2 NZ714831B2 NZ714831A NZ71483114A NZ714831B2 NZ 714831 B2 NZ714831 B2 NZ 714831B2 NZ 714831 A NZ714831 A NZ 714831A NZ 71483114 A NZ71483114 A NZ 71483114A NZ 714831 B2 NZ714831 B2 NZ 714831B2
- Authority
- NZ
- New Zealand
- Prior art keywords
- aggregates
- tau
- dipyrido
- pyrrole
- fluoro
- Prior art date
Links
Abstract
The present invention relates to a compound of general formula (I) wherein R is hydrogen or tritium; F is fluoro or 18fluoro; or to a pharmaceutically acceptable acid addition salt. Compounds of formula I include 2-(6-fluoro-pyridin-3-yl)-9H-dipyrido[2,3-b;3',4'-d]pyrrole, 3H-2-(6-fluoro-pyridin-3-yl)-9H-dipyrido[2,3-b;3',4'-d]pyrrole and [18F]-2-(6-fluoro-pyridin-3-yl)-9H-dipyrido[2,3-b;3',4'-d]pyrrole. The compounds may be used for binding and imaging tau aggregates and related beta-sheet aggregates including besides others beta-amyloid aggregates or alpha-synuclein aggregates. l)-9H-dipyrido[2,3-b;3',4'-d]pyrrole and [18F]-2-(6-fluoro-pyridin-3-yl)-9H-dipyrido[2,3-b;3',4'-d]pyrrole. The compounds may be used for binding and imaging tau aggregates and related beta-sheet aggregates including besides others beta-amyloid aggregates or alpha-synuclein aggregates.
Description
ARBAZOLE DERIVATIVES AS TAU-PET-LIGANDS
The t invention generally relates to a compound of general a
N N
N R
H I
wherein
R is hydrogen or tritium; and
F is fluoro or 18fluoro;
or to a ceutically acceptable acid addition salt.
Compounds of formula I include luoro-pyridinyl)-9H-dipyrido[2,3-b;3',4'-d]pyrrole,
3H(6-fluoro-pyridinyl)-9H-dipyrido[2,3-b;3',4'-d]pyrrole and [18F](6-fluoro-pyridin
yl)-9H-dipyrido[2,3-b;3',4'-d]pyrrole.
Compounds with similar generic basic structure are described in WO2009/102498 for in
vivo imaging of amyloid deposits for diagnosing Alzheimer’s disease. No tricyclic compounds
with 3 N atoms are described specifically.
It has been shown that the present compounds may be used for binding and imaging tau
aggregates and related beta-sheet aggregates including besides others beta-amyloid aggregates or
alpha-synuclein aggregates, especially for use in binding and imaging tau aggregates in
Alzheimer ts.
Alzheimer’s disease (AD) is a progressive neurodegenerative disorder terized by
cognitive e, irreversible memory loss, entation and language impairment (Arch.
. 1985, 42(11), 1097-1105). Postmortem examination of AD brain sections reveals
abundant senile plaques (SPs), composed of beta amyloid (Aβ) peptides, and numerous
neurofibrillary tangles (NFTs) formed by filaments of hyperphosphorylated tau protein.
Tau belongs to the family of microtubule-associated proteins and is mainly expressed in
s where it plays an important role in the assembly of tubulin monomers into microtubules
to constitute the neuronal microtubule network as tracks for axonal transport (Brain Res. Rev.
2000, 33(1), 95-130). Tau is translated from a single gene located on chromosome 17 and the
expression is developmentally regulated by an alternative splicing mechanism generating six
Pop/28.05.2014
ent isoforms in the human adult brain that can be guished by their number of binding
domains. The underlying mechanisms leading to tau hyperphosphorylation, ding and
aggregation are not well understood, but the deposition of tau aggregates follows a stereotyped
spatiotemporal pathway both at the intracellular levels as well as on the level of brain
aphy.
The recent discovery of tau gene mutations leading to frontotemporal dementia (FTD)
with parkinsonism linked to chromosome 17 has reinforced the predominant role attributed to tau
in the pathogenesis of neurodegenerative disorders and underlined the fact that distinct sets of
tau isoforms expressed in different neuronal populations could lead to ent pathologies
(Biochim. Biophys. Acta 2005, 1739(2) 240-250). egenerative diseases terized by
pathological tau accumulation are termed ‘tauopathies’ (Ann. Rev. Neurosci. 2001, 24, 1121-
1159). s AD and FTD, other tauopathies include progressive supranuclear palsy (PSP),
-predominant dementia, Pick's e, frontotemporal lobar degeneration (FTLD),
Down’s syndrome and .
A direct correlation has been established between the progressive involvement of
neocortical areas and the increasing severity of ia, suggesting that pathological tau
aggregates such as NFTs are a reliable marker of the neurodegenerative process. The degree of
NFT involvement in AD is defined by Braak stages (Acta Neuropathol. 1991, 82, 239-259).
Braak stages I and II are defined when NFT involvement is confined mainly to the
transentorhinal region of the brain, stages III and IV are diagnosed when limbic regions such as
the hippocampus are involved, and stages V and VI when extensive neocortical involvement is
found.
Presently, detection of tau aggregates is only possible by histological analysis of biopsy
or autopsy materials. In vivo imaging of tau pathology would provide novel insights into
deposition of tau aggregates in the human brain and allow to non-invasively examine the degree
of tau pathology, quantify changes in tau deposition over time, assess its correlation with
cognition and analyze the efficacy of an anti-tau therapy. Potential s for detecting tau
aggregates in the living brain must cross the blood-brain barrier and possess high ty and
specificity for tau aggregates. To this end, successful neuroimaging radiotracers must have
appropriate lipophilicity (logD 1-3) and low molecular weight (<450), show rapid clearance from
blood and low non-specific binding.
The object of the present application is to find an imaging tool which will improve
sis by identifying potential patients with excess of tau aggregates in the brain, which may
be likely to develop Alzheimer’s disease, and/or to at least provide the public with a useful
. It will also be useful to monitor the progression of the disease. When an au
aggregate drug becomes available, imaging tau tangles in the brain may e an essential tool
for monitoring treatment.
Described herein is a method of imaging tau-aggregate deposits, comprising
- introducing into a mammal a detectable quantity of a composition
- ng sufficient time for the compound of formula I to be associated with tauaggregate
deposits, and
- detecting the compound associated with one or more tau-aggregate deposits.
bed herein is a ceutical ition, containing compounds of formula I and
pharmaceutically able carriers, which may be used for identifying potential patients.
The following definitions of the general terms used in the present description apply
irrespective of whether the terms in question appear alone or in combination.
As used , the term "lower alkyl" denotes a saturated, i.e. aliphatic hydrocarbon group
including a straight or branched carbon chain with 1 – 7 carbon atoms. Examples for “alkyl” are
methyl, ethyl, n-propyl, and isopropyl.
3H denotes a tritium atom.
F denotes a fluoro atom or a 18fluoro atom.
The term “leaving group” denotes halogen or sulfonate. Examples of sulfonate are tosylate,
mesylate, triflate, nosylate or ate.
The term "pharmaceutically acceptable salt" or “pharmaceutically acceptable acid addition
salt” embraces salts with inorganic and organic acids, such as hydrochloric acid, nitric acid,
sulfuric acid, phosphoric acid, citric acid, formic acid, fumaric acid, maleic acid, acetic acid,
succinic acid, tartaric acid, methane-sulfonic acid, p-toluenesulfonic acid and the like.
The term “comprising” as used in this specification and claims means “consisting at least in
part of”. When interpreting statements in this ication and claims which include the term
“comprising”, other features besides the features prefaced by this term in each statement can also
be present. Related terms such as “comprise” and “comprises” are to be interpreted in similar
manner.
It has been found that the compounds of formula I may be used for binding and imaging tau
aggregates and d beta-sheet aggregates including besides others beta-amyloid aggregates or
alpha-synuclein aggregates.
In a first aspect, the invention provides a compound selected from:
luoro-pyridinyl)-9H-dipyrido[2,3-b;3',4'-d]pyrrole;
3H(6-fluoro-pyridinyl)-9H-dipyrido[2,3-b;3',4'-d]pyrrole;and
[18F](6-fluoro-pyridinyl)-9H-dipyrido[2,3-b;3',4'-d]pyrrole,
or a pharmaceutically acceptable acid addition salt thereof.
In a second aspect, the invention provides use of a nd according to the first aspect
in the manufacture of a composition for use in binding and imaging tau aggregates, myloid
aggregates or alpha-synuclein aggregates.
In a third aspect, the invention provides use of a compound according to the first aspect in
the manufacture of a composition for use in binding and imaging tau ates in Alzheimer
patients.
In a fourth aspect, the ion provides use of a compound according to the first aspect in
the manufacture of a composition for use in a tau-binding study.
In a fifth aspect, the ion provides use of a compound according to the first aspect in
the manufacture of a composition for use in diagnostic imaging of tau-aggregates in the brain of
a mammal.
In a sixth aspect, the invention provides a pharmaceutical preparation comprising a
compound according to the first aspect and a pharmaceutically acceptable carrier.
In this specification where reference has been made to patent specifications, other external
documents, or other sources of information, this is generally for the purpose of ing a
t for discussing the es of the invention. Unless specifically stated otherwise,
reference to such external documents is not to be construed as an admission that such documents,
or such sources of information, in any jurisdiction, are prior art, or form part of the common
general knowledge in the art.
In the description in this specification reference may be made to subject matter which is not
within the scope of the appended claims. That subject matter should be y identifiable by a
person d in the art and may assist in putting into practice the invention as defined in the
appended claims.
One embodiment of the present invention are compounds of formula I which compounds
are luoro-pyridinyl)-9H-dipyrido[2,3-b;3',4'-d]pyrrole, 3H(6-fluoro-pyridinyl)-9H-
dipyrido[2,3-b;3',4'-d]pyrrole and [18F](6-Fluoro-pyridinyl)-9H-dipyrido[2,3-b;3',4'-
d]pyrrole
One embodiment of the present invention are further compounds of formula I wherein R is
en, which compound is 2-(6-fluoro-pyridinyl)-9H-dipyrido[2,3-b;3',4'-d]pyrrole.
One embodiment of the present ion are further compounds of formula I wherein R is
tritium, for e the following compound 3H(6-fluoro-pyridinyl)-9H-dipyrido[2,3-
b;3',4'-d]pyrrole.
One ment of the invention are further compounds of formula I, wherein F is
ro, for example [18F](6-fluoro-pyridinyl)-9H-dipyrido[2,3-b;3',4'-d]pyrrole
The position for R in formula I, if R is tritium, is the most likely ones. But tritium may also
be found in small amounts in other positions of the molecule. Normally, only one of R is tritium.
The compounds of formula I may be used in binding and imaging tau aggregates, betaamyloid
aggregates, alpha-synuclein aggregates or huntingtin aggregates.
The preferred use of compounds of formula I is the use in binding and imaging tau aggregates in
Alzheimer patients.
Furthermore, the compounds of formula I may be used in a tau-binding study.
The nds of formula I are suitable for diagnostic imaging of tau-aggregates in the
brain of a .
The invention is also used for diagnostic imaging of tau-aggregate deposits in the brain of
a mammal.
The present compounds of formula I
N N
N R
H I
and their ceutically acceptable salts can be prepared by processes described below, which
process comprises
a) coupling a compound of a 2 (X = Cl, Br)
N N X
H 2
with suitable boronic acids or boronic acid esters of formula 3
OR' R
R N F 3,
n R’ is hydrogen or lower alkyl,
to afford compounds of formula I
N N
N R
H I
n R is hydrogen,
and, if desired, converting the obtained compound into pharmaceutically acceptable acid addition
salts or into compounds of a I, wherein R is tritium,;
b) coupling compounds of formula 4
N N
R N X 4 (X = Br, Cl, NO2)
with suitable fluorinating reagents selected from potassium fluoride or tetrabutylammonium
fluoride,
to afford compounds of formula I
N N
N R
H I
wherein the substituent R is hydrogen
and, if d, converting the compound obtained into pharmaceutically acceptable acid addition
salts or into compounds of formula I, wherein R is tritium
c) reacting a compound of formula I
N N
N R
H I
wherein R is hydrogen, with tritium gas in the ce of a catalyst, e.g. iridium, ium,
rhodium or palladium containing complexes in a suitable solvent, e.g. dichloromethane,
chlorobenzene, DMF, DMSO or mixtures thereof to afford compound of formula I
N N
N R
H I
wherein R is tritium, and, if desired, converting the compounds obtained into pharmaceutically
acceptable acid addition salts, or
d) dissolving a compound of formula
N R
H 10
in dimethylsulfoxide and sonicate prior to end of dment with aqueous [18]fluoride ion to
a compound of formula
N R
H I
and, if desired, converting the compounds obtained into pharmaceutically able acid
addition salts.
The following schemes 1-2 describe the processes for the preparation of compounds of
formula I in more detail. The starting materials are known compounds or may be prepared
according to methods known in the art.
The preparation of compounds of formula I of the present disclosure may be carried out
in sequential or convergent synthetic routes. The skills required for carrying out the reactions and
purifications of the ing products are known to those d in the art. The substituents and
indices used in the following description of the processes have the icance given herein
before unless indicated to the contrary.
In more detail, the compounds of formula I can be manufactured by the methods given
below, by the methods given in the examples or by analogous methods. Appropriate reaction
conditions for the individual reaction steps are known to a person d in the art. The reaction
sequence is not limited to the one displayed in schemes 1-2, however, depending on the starting
materials and their respective reactivity the sequence of reaction steps can be freely altered.
Starting als are either commercially ble or can be ed by methods analogous to
the methods given below, by methods described in references cited in the description or in the
examples, or by methods known in the art.
Scheme 1
N OR' N
X +
NH Cl N X' NH
PG PG Cl N X'
6
OR'R
N R N F N
3 R
N N X' N N
H H
2 R N F
OR'R
N R N F N
3 R
N N X' N N
PG PG
8 9 R N F
According to scheme 1, compounds of formula I, wherein R is hydrogen, can be prepared
starting from protected 4-amino-pyridines 5 (X = Cl, Br) and 2,6-di-halogenated pyridine
boronic acids 6 (R’ = H, lower alkyl). Transition-metal catalyzed cross-coupling ions
using a st system like e.g. Pd(OAc)2 and PPh3 and a base like e.g. triethylamine in a
le solvent like DMF results in bipyridines 7. Deprotection and olecular cyclisation
can be performed as one-pot procedure using a base like e.g. potassium carbonate and an
activator like e.g. 18-crown-6 in a suitable solvent like DMF and affords 1,6-diazacarbazole
intermediate 2. Final transformation into compounds of formula I can be accomplished by a
direct transition-metal catalyzed coupling on using appropriate pyridine boronic acids
3, a catalyst like e.g. Pd(dppf)Cl2 and a base like e.g. potassium ate in a suitable solvent
like DMF. Alternatively, 1,6-diazacarbazole 2 is first converted into protected intermediates 8
via reaction with a suitable reagent, e.g. di-tert-butyldicarbonate, in a suitable solvent like e.g.
DMF, followed by transition-metal catalyzed cross-coupling reaction towards intermediates 9
using appropriate pyridine boronic acids 3, a catalyst like e.g. Pd(dppf)Cl2 and a base like e.g.
potassium carbonate in a solvent like DMF. Deprotection is then leading to compounds of
formula I.
Scheme 2
N N
R R
N N N
H N
R N X R N F
4 I
According to scheme 2, a compound of formula I, wherein R is en, can be prepared by
treating a nd of formula 4 (X = Br, Cl, nitro); prepared according to the synthesis of
compounds of formula I described in scheme 1, with a suitable nating reagent like e.g.
potassium de or tetrabutylammonium fluoride in a suitable solvent like e.g. DMF or DMSO.
Compounds of formula I with R being tritium or F being 18F
N N
R N F I
may be ed in conventional manner as described in the specific examples. Compounds of
formula I do not contain simultaneously tritium and 18F.
Isolation and purification of the compounds
Isolation and purification of the compounds and intermediates described herein can be performed,
if desired, by any le separation or purification procedure such as, for example, filtration,
extraction, llization, column tography, thin-layer tography, thick-layer
chromatography, preparative low or high-pressure liquid chromatography or a combination of
these procedures. ic illustrations of suitable separation and isolation procedures can be
found by reference to the preparations and examples herein below. However, other equivalent
separation or isolation procedures could, of course, also be used. Racemic mixtures of chiral
compounds of formula I can be separated using chiral HPLC.
Salts of compounds of formula I
The compounds of formula I are basic and may be converted to a corresponding acid addition
salt. The conversion is accomplished by treatment with at least a iometric amount of an
appropriate acid, such as hydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid,
phosphoric acid and the like, and organic acids such as acetic acid, nic acid, glycolic acid,
pyruvic acid, oxalic acid, malic acid, malonic acid, succinic acid, maleic acid, fumaric acid,
tartaric acid, citric acid, benzoic acid, cinnamic acid, mandelic acid, methanesulfonic acid,
ethanesulfonic acid, p-toluenesulfonic acid, salicylic acid and the like. Typically, the free base is
dissolved in an inert organic t such as diethyl ether, ethyl acetate, form, ethanol or
methanol and the like, and the acid added in a similar solvent. The temperature is ined
between 0 °C and 50 °C. The resulting salt precipitates spontaneously or may be precipitated by
addition of a less polar solvent.
The acid addition salts of the basic nds of formula I may be converted to the
corresponding free bases by treatment with at least a stoichiometric lent of a suitable base
such as sodium or potassium hydroxide, potassium carbonate, sodium bicarbonate, ammonia,
and the like.
The compounds were investigated in accordance with the test given hereinafter.
TAU Radioligand-In-Vitro Displacement assay
This in vitro binding assay assesses the affinity of compounds for native tau aggregates. The
compounds are co-incubated with the well-established tau specific radioligand [3H]T808 and the
compound’s displacement y of 08 binding is determined by in vitro
autoradiography using human Alzheimer’s disease (AD) brain sections.
Materials
AD human brains are purchased from Banner Sun Health Research Institute (Sun City, AZ,
USA). Pathological diagnosis of AD is made according to standard NIA-Reagan Institute criteria
based on neuropathological data. The radioligand [3H]T808 was synthesized in-house ([3H][4-
(2-Fluoro-ethyl)-piperidinyl]-benzo[4,5]imidazo[1,2-a]pyrimidine, radiochemical purity
99.0 %). As a reference cold T808 is used (2-[4-(2-Fluoro-ethyl)-piperidinyl]-
benzo[4,5]imidazo[1,2-a]pyrimidine). For the autoradiography lm Imaging Plates (BAS-IP
TR 2025) are exposed to the sections and read with a FujiFilm IP reader (BAS-5000).
Method
Ten µm thick human AD brain sections are generated with a cryostat (Leica CM3050) at -17 °C
chamber ature and -15 °C object temperature. Sections are transferred to Histobond+
microscope slides (Marienfeld Laboratory Glasware). After drying for 3 hours at room
temperature the sections are stored at -20 °C. The sections are ted with the radioligand (10
nM) and the respective cold compound (at various concentrations) in 50 mM Tris buffer, pH 7.4
at room temperature for 30 min. After washing 3x 10 min at 4 °C in 50 mM Tris buffer, pH 7.4
and 3 quick dips in H2O dist. at 4 °C the sections are dried at 4 °C for 3 h. The sections are
placed in a FujiFilm Cassette (BAS 2025), d with an Imaging Plate for five days and
ards scanned with a tion of 25 µM per pixel.
Data is
The signal intensity (Dens - PSL/mm2) in the region of st (ROI) of the autoradiogram is
quantified with the software MCID analysis (version 7.0, Imaging ch Inc.).The specific
binding (SB) of [3H]T808 binding in absence or in presence of a compound is calculated by
subtracting the non-specific binding signal in the white matter, thus yielding SB[3H]T808 only and
und. The % displacement by the various compounds is calculated as following:
% displacement =100-(SBcompund/SB[3H]T808 100.
Validation data
In each experiment cold T808 is used as a positive internal control. Co-incubation of equimolar
amounts of hot and cold T808 is expected to reduce specific binding by approximately 50 %.
References
A.K. Szardenings et al. ‘Imaging agents for detecting neurological disorders’. US Patent
Application US20110182812
W. Zhang et al., ‘A highly selective and specific PET tracer for imaging of tau pathologies’.
Journal of Alzheimer’s Disease 31 (2012) 601-612.
Table 1
Structure Name %displacement of Expl.
[3H]T808 (10 nM)
2-(6-fluoro-pyridinyl)-9H- 43 1
N N dipyrido[2,3-b;3',4'-d]pyrrole
3H(6-fluoro-pyridinyl)- 2
F 9H-dipyrido[2,3-b;3',4'-
N N
3H d]pyrrole
N [18F](6-fluoro-pyridin- 3
N 3-yl)-9H-dipyrido[2,3-
N '-d]pyrrole
Figure 1:
diogram of 3H(6-fluoro-pyridinyl)-9H-dipyrido[2,3-b;3',4'-d]pyrrole
incubated with a human cortical brain n obtained from a Braak V staged AD patient. The
radioligand concentration was 3.2 nM. The igand shows a punctate staining of tau
aggregates in a layered distribution n.
The compounds of formula I and pharmaceutically acceptable salts thereof can be used in the
form of pharmaceutical ations. The pharmaceutical preparations can be administered in
form of injection solutions.
The compounds of formula I and pharmaceutically acceptable salts thereof can be processed
with pharmaceutically inert, inorganic or organic carriers for the production of pharmaceutical
preparations. Suitable carriers for the production of solutions and syrups are, for example, water,
polyols, sucrose, invert sugar, glucose and the like. Adjuvants, such as alcohols, polyols,
glycerol, vegetable oils and the like, can be used for aqueous ion solutions of water-soluble
salts of compounds of formula I, but as a rule are not necessary. Suitable carriers for
itories are, for example, natural or hardened oils, waxes, fats, semi-liquid or liquid polyols
and the like.
In addition, the pharmaceutical preparations can contain vatives, solubilizers,
stabilizers, g agents, emulsifiers, sweeteners, colorants, flavorants, salts for g the
osmotic pressure, buffers, masking agents or antioxidants. They can also contain still other
therapeutically valuable substances.
The dosage can vary within wide limits and will, of course, be fitted to the individual
requirements in each particular case.
Experimental Section:
Example 1
2-(6-Fluoro-pyridinyl)-9H-dipyrido[2,3-b;3',4'-d]pyrrole
N N
Step 1: tert-Butyl N-[3-(2,6-dichloropyridyl)pyridyl]carbamate
A pre-heated flask was evacuated and back-filled with argon several times and charged with tert-
butyl 3-iodopyridinylcarbamate (4.56 g, 14.2 mmol), 2,6-dichloropyridinylboronic acid
(5.46 g, 28.4 mmol), Pd(OAc)2 (320 mg, 1.42 mmol) and triphenylphosphine (371 mg, 1.41
mmol) under argon atmosphere. Triethylamine (4.32 g, 5.94 mL, 42.7 mmol) in DMF (137 mL)
was added and the reaction mixture was heated to 100 °C and stirred for 3 h. The solvent was
evaporated almost completely. Water was added and the crude product suspension was extracted
with ethyl acetate twice. The combined organic layer was washed with water (3 x), dried over
Na2SO4, filtered and the solvent was evaporated. ation of the crude product with
dichloromethane afforded 1.92 g of the desired product. The romethane phase was
evaporated and ed by flash chromatography (using silica gel and an ethyl acetate/heptane
gradient) to yield in total 3.39 g (~90 % purity, 63 % yield) of tert-butyl N-[3-(2,6-dichloro
pyridyl)pyridyl]carbamate as light yellow solid.
MS: m/z =340.1 (M+H)+.
Step 2: 2-Chloro-9H-dipyrido[2,3-b;3',4'-d]pyrrole
A suspension of tert-butyl N-[3-(2,6-dichloropyridyl)pyridyl]carbamate (264 mg, 776
µmol), potassium carbonate (215 mg, 1.55 mmol) and 18-crown-6 (226 mg, 854 µmol) in DMF
(15.8 mL) was heated to 100 °C and stirred for 3 h under an here of argon. Water was
added and the crude product suspension was extracted with ethyl acetate twice. The combined
organic layer was washed with water (twice), brine, dried over Na2SO4, filtered and the solvent
was evaporated. Trituration of the crude product with little methanol afforded ro-9H-
dipyrido[2,3-b;3',4'-d]pyrrole (105 mg, 63 % yield) as light yellow solid.
MS: m/z = 204.3 (M+H)+.
Step 3: 2-Chloro-dipyrido[2,3-b;3',4'-d]pyrrolecarboxylic acid tert-butyl ester
A suspension of sodium hydride (26.5 mg, 607 µmol) in dry DMF (1.5 mL) was cooled to 0 °C
and under argon a solution of 2-chloro-9H-dipyrido[2,3-b;3',4'-d]pyrrole (103 mg, 506 µmol) in
dry DMF (3.0 mL) was added. Stirring was continued at 0 °C for 10 min and at r.t. for 30 min.
After cooling down to 0 °C and addition of di-tert-butyl dicarbonate (132 mg, 141 µL) in dry
DMF (0.75 mL) was added and stirring was continued at r.t. overnight. Water was added and the
reaction mixture was ted twice with ethyl e. The combined organic layer was washed
with water (twice) and brine, dried over Na2SO4, filtered and evaporated. 2-Chloro-dipyrido[2,3-
b;3',4'-d]pyrrolecarboxylic acid utyl ester was obtained after purification by flash
tography (using silica gel and a methanol/dichloromethane gradient) as off-white solid
(113 mg, 73.5 %).
MS: m/z = 304.1 (M+H)+.
Step 4: 2-(6-Fluoro-pyridinyl)-dipyrido[2,3-b;3',4'-d]pyrrolecarboxylic acid utyl ester
A microwave vessel was charged under argon atmosphere with 2-chloro-dipyrido[2,3-b;3',4'-
d]pyrrolecarboxylic acid tert-butyl ester (100 mg, 329 µmol), 2-fluoro(4,4,5,5-tetramethyl-
1,3,2-dioxaborolanyl)pyridine (147 mg, 658 µmol), potassium carbonate (137 mg, 988 µmol)
and 1,1'-bis(diphenylphosphino)ferrocene-palladium(II)dichloride dichloromethane complex
(10.8 mg, 13.2 µmol) and the vessel was sealed, evacuated and back-filled with argon. DMF (7
mL) was added and the reaction mixture was heated to 90 °C and stirred for 17 h. The reaction
mixture was filtered. Water was added to the filtrate and the reaction mixture was extracted
twice with ethyl acetate. The combined organic layer was washed with water (3 x), dried over
Na2SO4, filtered and evaporated. Trituration of the crude product e with little methanol
afforded 2-(6-fluoro-pyridinyl)-9H-dipyrido[2,3-b;3',4'-d]pyrrole (m/z = 265.1 (M+H)+) as
light red solid (23 mg with 80 % , 21 %). The liquid was evaporated and purified by flash
chromatography (using silica gel and a methanol/dichloromethane gradient) to afford 2-(6-
fluoro-pyridinyl)-dipyrido[2,3-b;3',4'-d]pyrrolecarboxylic acid tert-butyl ester as off-white
solid (12 mg, 10 %).
MS: m/z = 365.2 (M+H)+.
Step 5: 2-(6-Fluoro-pyridinyl)-9H-dipyrido[2,3-b;3',4'-d]pyrrole
A light yellow solution of 2-(6-fluoro-pyridinyl)-dipyrido[2,3-b;3',4'-d]pyrrolecarboxylic
acid tert-butyl ester (22 mg, 60.4 µmol) and trifluoroacetic acid (33.3 µL, 432 µmol) in
romethane (0.5 mL) was d at r.t. overnight. After cooling to 0 °C triethylamine (70
µL, 503 µmol) was added and all volatiles were removed. The crude material was purified by
preparative HPLC (using a Gemini C18 column and a water with 0.1% triethylamine /
acetonitrile gradient) to afford 2-(6-fluoro-pyridinyl)-9H-dipyrido[2,3-b;3',4'-d]pyrrole as offwhite
solid (14 mg, 88 %).
MS: m/z = 265.1 (M+H)+.
Example 2
3H(6-Fluoro-pyridinyl)-9H-dipyrido[2,3-b;3',4'-d]pyrrole
N N
N H
In a 2 ml tritiation flask, 2-(6-fluoro-pyridinyl)-9H-dipyrido[2,3-b;3',4'-d]pyrrole (2.0 mg, 7.6
µmol; example 1) and Crabtree’s st (9.14 mg, 11.4 µmol) were dissolved in
dichloromethane (0.8 mL) and DMF (0.2 mL). The flask was ed to the tritium manifold
(RC-TRITEC) and ed by freeze-pump-thaw. Tritium gas was uced, and the light
orange solution was vigorously stirred for 4 hours in an atmosphere of tritium at 450 mbar. The
solution was cooled by liquid nitrogen and the excess tritium gas in the reaction vessel was
reabsorbed on a uranium-trap for waste-tritium. The solvent was lized off and labile
tritium was removed by lyophilization with a 9:1-mixture of ethanol and water (3 x 1 mL) and
toluene (2 x 1 mL). The remaining brownish oil was dissolved in ethanol (1.5 mL) and
transferred on a SCX-2 cation exchanger. Remaining catalyst was eluted with MeOH (10 mL)
and discarded, and the product was eluted with NH3 in MeOH (3.5 N, 10 mL), collected
separately and concentrated under reduced pressure. The crude product was purified by
preparative HPLC (XBridge Prep, 5 µm, 10 x 250 mm) using acetonitrile, water, and pH 7 buffer
as eluent. 37 MBq (1 mCi) of the title compound were obtained with a radiochemical purity of
99% and a specific activity of 936 GBq/mmol (25.3 Ci/mmol), determined by MS spectrometry.
The compound was stored as a pH 7 buffer/DMSO solution.
MS: m/z = 265.1 , 267.1 [M(3H1)+H]+, 269.1 [M(3H2)+H]+
Example 3
[18F](6-Fluoro-pyridinyl)-9H-dipyrido[2,3-b;3',4'-d]pyrrole
a) 2-(6-Nitro-pyridinyl)-9H-dipyrido[2,3-b;3',4'-d]pyrrole
In a 50 mL flask (evaporated and purged with Ar), 2-chloro-dipyrido[2,3-b;3',4'-d]pyrrole
carboxylic acid utyl ester (285 mg, 938 µmol), 2-nitropyridineboronic acid pinacol ester
(469 mg, 1.88 mmol), 1,1'-bis(diphenylphosphino)ferrocene-palladium(II)dichloride
dichloromethane complex (34.5 mg, 42.2 µmol) and K2CO3 (389 mg, 2.81 mmol) were
ed. DMF (24 mL) was added and the tube was sealed, evaporated and purged with Ar.
The reaction mixture was heated to 90 °C and stirred for 18 h. Filtration through Celite and
subsequently through small silica gel pad (neutral, 60A, mesh 32-63) was followed by rinsing
with ient DMF and evaporation to dryness. The brown solid is dissolved in DMF (20 mL)
and DMSO was added until an almost clear on resulted. After filtration, the solvents are
evaporated to almost dryness. Purification by prep-HPLC provided the title compound (37 mg,
13 %) as a yellow solid. MS m/z: 292.2 [M+H] +
b) [18F](6-Fluoro-pyridinyl)-9H-dipyrido[2,3-b;3',4'-d]pyrrole
The precursor, (0.7 ± 0.3 mg) was dissolved in 400 µL dimethylsulfoxide and sonicated prior to
end of bombardment (EOB). At EOB, the aqueous [18F]fluoride ion, produced by proton
bombardment of [18O]-enriched water, was trapped on an ion exchange column. The ion
exchange column was eluted with 150 µL of a stock solution of Krytpofix 2.2.2/potassium
carbonate (48 mg of fix 2.2.2 and 10 mg potassium carbonate dissolved in 600 µL of 1:1
acetonitrile:water) into the reaction vial followed by 250 µL acetonitrile. The fluoride solution
was ated to dryness at 110 ˚C via nitrogen flow and further dried azeotropically by two
additions of itrile (250 µL each). The reaction vial was ly transferred to the
microwave cavity (Resonance Instruments) and cooled with compressed air for 2 minutes. The
precursor was added and then microwaved at 50 watts for 240 seconds after which the solution
was ed with 1 mL of water.
The reaction solution was diluted 3 mL triethylamine (TEA) buffer (pH 7.2) then injected onto
the semi-preparative HPLC column (XBridge Cl8, 10 µm, 10x150 mm) eluted with 15:85
methanol:TEA buffer (pH 7.2) at 15 mL/min.
The HPLC effluent was monitored at 254 nm and an in-line radioactivity detector. The
semipreparative chromatogram was ed and the [18F]- product peak was collected in 50
mL of water and reformulated using an automated SPE module. The t solution was eluted
h a Waters C-18 SepPak Plus, washed with 10 mL of Milli-Q water, then eluted with 1 mL
of absolute l followed by 10 mL of normal saline into the final product vial via a 0.22 µm
Millipore FG sterilizing filter.
Aliquots were removed from the final bottle for quality control analysis. Analytical HPLC
(XBridge C18, 3.5 µm, 4.6x100 mm) elute with 40:60 methanol:TEA buffer (pH 7.2) at 2
mL/min monitored at 350 nm was performed to determine radiochemical and chemical purity,
ic activity and chemical identity.
The 57-minute radio-synthesis of [18F](6-fluoro-pyridinyl)-9H-dipyrido[2,3-b;3',4'-
d]pyrrole produced an average final product of 330.5 mCi, 26.1 % (n=2) non-decay corrected
yield. The final product had an average specific radioactivity of 24,684 mCi/µmole and
radiochemical purity of 99 %.
Claims (3)
1. A compound selected from:
2-(6-fluoro-pyridinyl)-9H-dipyrido[2,
3-b;3',4'-d]pyrrole; 5 3H(6-fluoro-pyridinyl)-9H-dipyrido[2,3-b;3',4'-d]pyrrole;and [18F](6-fluoro-pyridinyl)-9H-dipyrido[2,3-b;3',4'-d]pyrrole, or a pharmaceutically acceptable acid addition salt thereof. 2. A compound according to claim 1 for use in binding and imaging tau aggregates, beta-amyloid 10 aggregates or alpha-synuclein aggregates. 3. A compound according to claim 1 for use in binding and imaging tau aggregates in Alzheimer patients. 15 4. A compound according to claim 1 for use in a tau-binding study. 5. A compound according to claim 1 for use in diagnostic imaging of tau-aggregates in the brain of a mammal. 20 6. Use of a compound according to claim 1 in the cture of a ition for use in g and g tau aggregates, beta-amyloid aggregates or alpha-synuclein aggregates. 7. Use of a compound according to claim 1 in the manufacture of a ition for use in binding and imaging tau aggregates in Alzheimer patients. 8. Use of a compound according to claim 1 in the manufacture of a composition for use in a taubinding study. 9. Use of a compound according to claim 1 in the manufacture of a composition for use in 30 diagnostic imaging of tau-aggregates in the brain of a . 10. A pharmaceutical preparation sing a compound according to claim 1 and a pharmaceutically acceptable carrier. 11. A compound ing to any one of claims 1 to 5, ntially as herein described with reference to any example thereof. 12. Use according to any one of claims 6 to 9, substantially as herein described with reference to 5 any example thereof. 13. A pharmaceutical preparation according to claim 10, substantially as herein described with reference to any example thereof. -
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP13187764.9 | 2013-10-08 | ||
EP13187764 | 2013-10-08 | ||
PCT/EP2014/071283 WO2015052105A1 (en) | 2013-10-08 | 2014-10-06 | Diazacarbazole derivatives as tau-pet-ligands |
Publications (2)
Publication Number | Publication Date |
---|---|
NZ714831A NZ714831A (en) | 2021-09-24 |
NZ714831B2 true NZ714831B2 (en) | 2022-01-06 |
Family
ID=
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US11058781B2 (en) | Diazacarbazole derivatives as tau-PET-ligands | |
AU2017231781B2 (en) | Bicyclic compounds for diagnosis and therapy | |
JP6130055B2 (en) | 2-Phenylimidazo [1.2-A] pyrimidine as a contrast agent | |
EP3049411B1 (en) | Imidazo[1,2-a]pyridin-7-amines as imaging tools | |
JP7100043B2 (en) | Bis-heteroaryl derivative as a modulator of protein aggregation | |
CN112533928A (en) | Novel compounds for use in diagnostics | |
WO2023285661A1 (en) | Novel compounds for the diagnosis of tdp-43 proteinopathies | |
NZ714831B2 (en) | Diazacarbazole derivatives as tau-pet-ligands | |
BR112016000622B1 (en) | DIAZACARBAZOLE DERIVATIVES AS TAU-PET LINKS, THEIR MANUFACTURING PROCESS AND PHARMACEUTICAL PREPARATION | |
JP6946412B2 (en) | Tau PET Imaging Ligand | |
CN117940435A (en) | Novel compounds for diagnosing TDP-43 proteinopathies | |
EA039208B1 (en) | Tau pet imaging ligands |