J. Malmquist and P. Ström
heptan-3-yl)borane ([ꢂ]-DIP-Cl, 240mg, 0.75mmol) at 0ꢀC. The mixture The combined organics were dried over sodium sulfate, filtered, and
was stirred overnight at 21 ꢀC. Diethanolamine (150 mg, mmol) was added, concentrated. The residue was purified by chromatography on silica gel
and the resulting slurry was filtered and concentrated. The residue was (40 g) using heptane and ethyl acetate 9:1. Pooled fractions were
purified by chromatography on silica gel using dichloromethane as eluent concentrated to give 16 (601mg, 2.33 mmol) in 51% yield, consistent with
to give 9 (0.9GBq, 0.5mmol) with a purity of > 98%. The product was used reference material. LC-MS m/z 256 (10%), 258 (100%) [(M + H)+].
as is in the solution. GC-MS m/z 121 (10%), 123 (100%), 124 (11%) [(M-H)-].
[4-14C]-(R)-tert-butyl 1-hydroxy-4-methylpentan-2-
[1-14C]- ((R)-1-Chloro-ethyl)-benzene (10)
ylcarbamate (17)
A
slurry of [20-14C]-(R)-tert-butyl 2,2-dimethyl-4-(20-methylprop-1-enyl)
Triphenylphosphine (157 mg, 0.6 mmol) in tetrahydrofuran (2 mL) was
added dropwise over 15 minutes to solution of N-chloro-succinimide
(80 mg, 0.6 mmol) cooled to 0 ꢀC. The mixture was warmed to room
temperature and stirred for half an hour. [1-14C]-(S)-1-Phenyl-ethanol
(9, 0.5 mmol, 0.9 GBq) in tetrahydrofuran (2 mL) was added at 0 ꢀC. The
reaction was completed after stirring overnight at 21 ꢀC according to
TLC. The mixture was concentrated, and the residue was purified by
chromatography on silica gel using heptane and ethyl acetate 8:1. The
pooled fractions were concentrated to ~2 mL. 10 (0.5 mmol, 0.9 GBq)
was used as is in the next step as a heptane solution. GC-MS m/z 140
(10%), 142 (100%), 143 (10%), 144 (30%), 145 (4%) [M-].
oxazolidine-3-carboxylate (16, 601 mg, 2.33 mmol) and palladium (80mg,
10% on carbon) in methanol (10 mL) was connected to hydrogen (1atm).
The slurry was filtered when reaction was > 95% completed according to
TLC after 5 days. The concentrated residue was purified by chromatography
on silica gel (40 g) using dichloromethane and methanol 98:2. Pure fractions
were pooled and concentrated to give 17 (500mg, 2.28 mmol) in 98% yield,
consistent with the reference material.
[4-14C]-(R)-2-amino-4-methylpentan-1-ol trifluoroacetate (18)
[4-14C]-(R)-tert-butyl 1-hydroxy-4-methylpentan-2-ylcarbamate (17, 500mg,
2.28 mmol) in trifluoroacetic acid (1mL) and dichloromethane (10 mL) was
stirred overnight at 21ꢀC. The mixture was concentrated to give 530mg
of 18, consistent with the reference material.
[1-14C]-(1-Bromo-ethyl)-benzene (11)
Borane trimethylamine complex (175 mg, 2.4 mmol) was added to an
ice-cooled solution of [1-14C]-acetophenon (8, ~3.8 GBq, ~1.9 mmol) in
chloroform (5 mL) under argon. Bromine (0.8 mL, 4 M in chloroform,
3 mmol) was added at 0 ꢀC until a yellow color persisted. The mixture
was heated to 50 ꢀC for 10 minutes. Water (4 mL) was added, and the
organic phase was separated, dried over sodium sulfate, and filtered to
give 11 (~3.5 GBq) in chloroform. The product was used directly in the
next step. GC-MS m/z 184 (10%), 186 (100%), 188 (93%) [M+].
[4-14C]-(R)-2-(2-amino-5-((S)-1-phenylethylthio)thiazolo
[4,5-d]pyrimidin-7-ylamino)-4-methylpentan-1-ol ([4-14C]1)
A
solution of [4-14C]-(R)-2-amino-4-methylpentan-1-ol trifluoroacetate
(18, 530 mg, 2.27 mmol), ethyl-diisopropyl-amine (2 mL, 11.5 mmol) and (S)-
7-chloro-5-(1-phenylethylthio)thiazolo[4,5-d]pyrimidin-2-amine4 (19, 687mg,
2.13 mmol) in N-methyl-pyrrolidone was heated at 120 ꢀC overnight. Ice
(30 mL) was added to the reaction mixture, and the solution was extracted
with dichloromethane (4ꢁ 4mL). The organic phase was dried over sodium
sulfate, filtered, and concentrated. The residue was purified by chromato-
graphy on silica gel (40 g) using ethyl acetate and dichloromethane 3:7
and then dichloromethane-methanol 9:1. The pooled fractions were
concentrated to dryness, and the residue was purified by preparative HPLC
using 48% acetonitrile on the 50 mm column. The product containing
fractions were pooled and concentrated. The residue was purified by
chromatography on silica gel (20 g) using a gradient of ethyl acetate in
dichloromethane. Pooled fractions were concentrated to give [4-14C]1
(44 mg, 229 MBq) at a specific activity of 2.1GBq/mmol and a total yield
of 5% from [2-14C]-2-iodopropane. LC-MS m/z 404.3 (11%), 406.3 (100%),
407.3 (38%) [(M+ H)+].
[10-14C]-(R)-2-(2-amino-5-((S)-1-phenylethylthio)thiazolo[4,5-d]
pyrimidin-7-ylamino)-4-methylpentan-1-ol ([10-14C]1)
Route 1: Sodium borohydride (7mg, 0.2mmol), ethyldiisopropylamine
(180 mL,1.0mmol), and [1-14C]-((R)-1-chloro-ethyl)-benzene (10, 0.5mmol,
0.9GBq) were added to a solution of (R)-2-(2-amino-5-mercaptothiazolo
[4,5-d]pyrimidin-7-ylamino)-4-methylpentan-1-ol4 (6, 225mg, 0.75mmol)
in dimethylsulfoxide (2mL) under nitrogen. The mixture was heated to
40 ꢀC overnight. Ice (7mL) was added to the reaction mixture, and the
mixture was extracted with dichloromethane (3ꢁ 2 mL). The organic
phase was dried over sodium sulfate, filtered, and concentrated. Purifica-
tion was affected by chromatography on silica gel using ethyl acetate
and dichloromethane (7:3) to give 33 mg. The enriched diastereomeric
mixture was separated on reversed phase HPLC using 50% acetonitrile.
The pooled fractions were concentrated to half the volume and extracted
with dichloromethane (3ꢁ 5 mL). The solution was dried over sodium
sulfate, filtered, and concentrated to give [10-14C]1 (14 mg, 55MBq,
1.6GBq/mmol) with a purity of 99.9% in 7.6% total yield from [14C]benzoic
acid. LC-MS m/z 404.3 (16%), 406.3 (100%), 407.3 (30%) [(M + H)+].
Route 2: As route 1 with [1-14C]- (1-bromo-ethyl)-benzene (11, ~3.5GBq,
~1.7mmol) instead of [1-14C]-((R)-1-chloro-ethyl)-benzene (10) to give
[10-14C]1 ( 78 mg, 385 MBq, 2.0GBq/mmol) with a purity of 98.0% and
9.3% total yield from [14C]benzoic acid. LC-MS is similar as previously
mentioned.
1-Hydroxy-3-methylbutane-1-sulfonate sodium salt (20)
To sodium metabisulfite (4.6g, 24 mmol) in water (50mL), 3-methylbutanal
(4.17 g, 48 mmol) was added, and the mixture was stirred vigorously at
50 ꢀC for 30 minutes. Upon cooling to room temperature, the product
precipitated out and was isolated by filtration. The product was dried in
vacuum to give 20 (4.6g, 24mmol) in a 50% yield, consistent with the
reference material.
N-acetyl-[1-14C]-leucine (21)
[20-14C]-(R)-tert-butyl 2,2-dimethyl-4-(20-methylprop-1-enyl)
oxazolidine-3-carboxylate (16)
To a solution of sodium 1-hydroxy-3-methylbutane-1-sulfonate (20, 353mg,
1.87 mmol) in water (5 mL), potassium [14C]cyanide (125mg, 1.87mmol) was
added, and the reaction was stirred for 4 hours. The mixture was extracted
Butyl lithium (2.8 mL, 1.6 M) was added to a solution of triphenyl-2-[14C]- with diethyl ether (3ꢁ 5 mL) and was dried with sodium sulfate and filtered.
isopropylphosphonium iodide6 (1.98 g, 4.6 mmol, 2.1 GBq/mmol) in tetra- The ether was evaporated, and the residue was dissolved in ethanol (2mL).
hydrofuran (15 mL) at ꢂ78 ꢀC under an argon atmosphere. The reaction Ammonia (2.0 mL, 26 mmol, 28%) was added, and the mixture was stirred
was warmed to 0 ꢀC for 1 hour and then cooled to ꢂ78 ꢀC. A solution overnight. The reaction mixture was concentrated under a stream of
of Garner’s aldehyde7 (1.98 mg, 6.4 mmol) in tetrahydrofuran (3mL) was nitrogen, and the residue was extracted with diethyl ether (2ꢁ 5mL). The
added, and the reaction warmed to room temperature overnight.
ethereal phase was dried over sodium sulfate, filtered, and concentrated.
Ammonium chloride (20 mL, sat.) was added, and the tetrahydrofuran Hydrobromic acid (1 mL, 48%) was added to the residue, and the resulting
was evaporated. The residue was extracted with ethyl acetate (3ꢁ 5 mL). solution was heated at 110ꢀC for 1 hour. The reaction mixture was
J. Label Compd. Radiopharm 2012
Copyright © 2012 John Wiley & Sons, Ltd.