Stereoselective trimethylsilylation of α- and β-galactopyranoses. (15th February 2019) - Asami, Yuri
Abstract: Trimethylsilylation of the anomeric hydroxyl groups of tetra- O -benzyl and tetra- O -acetyl galactopyranoses was investigated. Stereoselective formation of β-trimethylsilyl glycoside (β-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 α-TMS glycoside after silica gel column chromatography. A reaction of acetylated compound using TMS-trifluoromethanesulfonate–2, 6-lutindine selectively yielded α-TMS glycoside. Graphical abstract: Image 1 Highlights: Trimethylsilylation reactions at anomeric position of acetyl and benzyl protected galactopyranoses were investigated. Trimethylsilylation reaction mechanisms were investigated. It was found that trimethylsilyl amines and imidazole undergo addition of silyl group at aldehyde forming silyoxonium intermediate. Trimethylsilyl amines and imidazole seemed proseed via addition of silyl group of aldehyde form. We successfully synthesized α- and β-TMS glycosides of galactopyranoses stereospecifically.