GLYCOSYLIMIDATES .72. N-TETRACHLOROPHTHALOYL-PROTECTED TRICHLOROACETIMIDATE OF GLUCOSAMINE AS GLYCOSYL DONOR IN OLIGOSACCHARIDE SYNTHESIS

N-Tetrachlorophthaloyl (TCP) protection of glucosamine could be readily carried out with tetrachlorophthalic anhydride and then treatment with acetic anhydride in pyridine. Ensuing reaction with N2H4 . HOAc and then base-catalyzed activation with trichloroacetonitrile afforded N-TCP protected glucosamine donor 2. Glycosylation of accepters 3a-d in acetonitrile with Sn(OTf)(2) as the catalyst gave beta-glycosides 4a-d in high yields, thus exhibiting the high reactivity and diastereoselectivity of 2. For TCP cleavage NaBH4 reduction followed by acid catalyzed phthalide formation and then treatment with acetic anhydride was employed, thus giving N-acetylglucosamine containing oligosaccharides Sa,c,d in a convenient, highyielding procedure.