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Synthesis of 1,1′‐carbonyldimidazole‐ 1‐ 14 C and its use in preparing a methoxy(polyethylene)glycol semicarbazide linker
Author(s) -
Walker Donald G.,
Leister William H.,
Weaner Larry E.
Publication year - 1995
Publication title -
journal of labelled compounds and radiopharmaceuticals
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.432
H-Index - 47
eISSN - 1099-1344
pISSN - 0362-4803
DOI - 10.1002/jlcr.2580360708
Subject(s) - chemistry , toluene , semicarbazide , yield (engineering) , phosgene , hydrazine (antidepressant) , dichloromethane , polyethylene glycol , nuclear chemistry , imidazole , organic chemistry , chromatography , solvent , materials science , metallurgy
Abstract Reaction of N ‐(trimethylsilyl)imidazole ( 2 ) with phosgene‐ 14 C in toluene afforded 92 w/w % pure ( 1 H NMR) 1,1′‐carbonyldimidazole‐1‐ 14 C ( 3 ) in near quantitative yield. Activation of MPEG‐amine 4 by reaction with 3 in dichloromethane afforded intermediate 5 in situ. Further reaction with hydrazine in toluene at 50°C and reprecipitation from 2‐propanol afforded crude 1 (81%). A two‐step chromatographic purification of this material followed by reprecipitation from 2‐propanol gave MPEG‐semicarbazide linker 1 . This material had a chemical purity estimated at 98%, a radiochemical purity of 95%, a specific activity of 7.7 μCi/mg (37.6 mCi/mmol) and a number‐average molecular weight of 4885 ( 1 H NMR).