Open AccessPreparation of Nucleosides Derived from 2-Nitroimidazole and d -Arabinose, d -Ribose, and d -Galactose by the Vorbrüggen Method and Their Conversion to Potential Precursors for Tracers To Image Hypoxia
Author(s) -
Anna Schweifer,
Friedrich Hammerschmidt
Publication year - 2011
Publication title -
journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.2
H-Index - 228
eISSN - 1520-6904
pISSN - 0022-3263
DOI - 10.1021/jo200727k
Subject(s) - chemistry , anomer , ribose , arabinose , trifluoromethanesulfonate , silylation , pyridine , galactose , stereochemistry , glycoside , combinatorial chemistry , organic chemistry , catalysis , xylose , fermentation , enzyme
2-Nitroimidazole was silylated using hexaethyldisilazane and then reacted with 1-O-acetyl derivatives of D-arabinose, D-ribose, and D-galactose in acetonitrile at mild temperatures (-20 °C to rt), catalyzed by triethylsilyl triflate (Vorbrüggen conditions). The α-anomer was formed in the former case and the β-anomers in the latter two cases (highly) selectively. When D-arabinose and D-ribose were silylated with tert-butyldiphenylsilyl chloride in pyridine at the hydroxyl groups at C-5 and acetylated at the other ones in a one-pot reaction, mixtures of anomeric 1-O-acetyl derivatives were obtained. These were coupled by the Vorbrüggen method and then deblocked at C-5 and tosylated to give precursors for tracers to image hypoxia in four steps without using Hg(CN)(2) necessary for other methods. The Vorbrüggen conditions enable a shorter route to azomycin nucleoside analogues than the previous coupling procedures.