Selectivity in the SmI2-induced deoxygenation of thiazolylketoses for formyl C-glycoside synthesis and revised structure of C-ribofuranosides

Deoxygenation of thiazolylketose acetates Using SmI2-(CH2OH)(2) or TMSOTf-E t3SiH affords thiazolyl C-glycosides with opposite alpha/beta ratios. Exami nation of the thiazolyl alpha- and beta -C-ribofuranoside pair by NOE exper iments reveals that the earlier configuration assigned to one of these isom ers has to be revised. Having prepared authentic anomeric a- and P-ribofura nose aldehydes from the corresponding thiazolyl C-glycosides by cleavage of the thiazole ring, each aldehyde was transformed into (1 -->6)-C-disacchar ides via Wittig olefination with a galactose 6-phosphorane. (C) 2001 Elsevi er Science Ltd. All rights reserved.