Stereoselective Trimethylsilylation Of Alpha- And Beta-Galactopyranoses

Trimethylsilylation of the anomeric hydroxyl groups of tetra-O-benzyl and tetra-O-acetyl galactopyranoses was investigated. Stereoselective formation of beta-trimethylsilyl glycoside (beta-TMS glycoside) of benzyl protected compound was achieved using N-trimethylsilyl diethylamine. In the course of the investigation of the selective synthesis of TMS galactosides using TMS-imidazole, we observed the formation of an intermediate, which was converted predominantly into alpha-TMS glycoside after silica gel column chromatography. A reaction of acetylated compound using TMS-trifluoromethanesulfonate-2,6-lutindine selectively yielded alpha-TMS glycoside.