Stereoselective synthesis of O-serinyl/threoninyl-2-acetamido-2-deoxy-α- or β-glycosides

General glycosidation methodology has been developed which can selectively provide 2-acetamido-2-deoxy-α- or β-glycosides of β-hydroxy-α-amino acid derivatives [glucopyranoside-(8, 43), galactopyranoside- (9, 13), mannopyranoside- (10), lactoside analogs (11, 38) and 3-O-β-galactopyranosyl-mannopyranoside (12)] stereoselectively in excellent yield from the highly nucleophilic α-imino esters (Schiff bases) of l-serine and l-threonine. Various glycosides were converted via their amino and acetamido derivatives to Fmoc-protected serinyl- or threoninyl-glycosides (24-28, 37, 41, 46) which are all suitable building blocks for the solid-phase synthesis of O-glycopeptides. Complete ¹H- and ¹³C-NMR data are provided for all compounds.