New Methods Suitable for Large-Scale Preparation of Sialoglycosides.

Abstract

Facile method applicable for large-scale preparation of sialoglycosides were developed by using Lewis acid alone or the combination of trimethylsilyl chloride and lewis acid as the activator. Glycosylation catalyzed by zinc bromide using methyl (5-acetamido-4, 7, 8, 9-tetra-O-acetyl-3, 5-dideoxy-β-D-glycero-D-glacto-2-nonulopyranosyl chlorid)onate as a glycosyl donor afforded predominantly α-sialoglycosides. In the reaction using methyl 5-acetamido-2, 4, 7, 8, 9-penta-O-acetyl-3, 5-dideoxy-β-D-glycero-D-galacto-2-nonulopyranosonate as the glycosyl donor, with tin(IV) chloride as an activator, β-sialoglycosides were obtained stereoseloctively, whereas the combination of trimethylsilyl chloride and zinc triflate as an activator afforded predominantly α-sialoglycosides.