Regioselective and stereocontrolled syntheses of protected L-glycosides from L-arabinofuranosides

摘要

Synthesis of novel mono- and di-O-protected L-arabinofuranoside derivatives was described via regioselective base-catalyzed acylations of methyl alpha- and beta-L-arabinofuranosides with acyl chlorides. A new method for selective 3(2)-O-acylation of 5-O-silyl (trityl) L-arabinofuranosides was investigated based upon generation of organoboron compounds using L-Selectride and subsequent reaction of salt carbohydrate species with pivaloyl or 4-chlorobenzoyl chloride as the electrophile. Syntheses of methyl 2,3-anhydro-L-furanosides were accomplished from selectively protected methyl L-arabinofuranosides. 2(3)-Deoxy-L-pentofuranosides, including 2-deoxy L-ri-bofuranoside, and their 5-O-blocked derivatives were prepared by stereoselective reductions of 2,3-anhydro-L-furanosides with L-Selectride.