STEREOSELECTIVE SYNTHESIS OF O-SERINYL THREONINYL-2-ACETAMIDO-2-DEOXY-ALPHA-GLYCOSIDES OR YL/THREONINYL-2-ACETAMIDO-2-DEOXY-BETA-GLYCOSIDES/

General glycosidation methodology has been developed which can selecti vely provide 2acetamido-2-deoxy-alpha- or beta-glycosides of beta-hydr oxy-alpha-amino acid derivatives [glucopyranoside- (8, 43), galactopyr anoside- (9, 13), mannopyranoside- (10), lactoside analogs (11, 38) an d 3-O-beta-galactopyranosyl-mannopyranoside (12)] stereoselectively in excellent yield from the highly nucleophilic a-imino esters (Schiff b ases) of L-serine and L-threonine. Various glycosides were converted v ia their amino and acetamido derivatives to Fmoc-protected serinyl- or threoninyl-glycosides (24-28, 37, 41, 46) which are all suitable buil ding blocks for the solid-phase synthesis of O-glycopeptides. Complete H-1- and C-13-NMR data are provided for all compounds.