Beta-selective glycosylations with masked D-mycosamine precursors.

[reaction: see text]. Both an intramolecular aglycon delivery (IAD) method and an intermolecular S(N)2 displacement method were examined for beta-selective glycosylations of cholesterol with D-mycosamine. An anomeric sulfoxide, sulfide, selenide, and fluoride were all successfully used as glycosyl donors in IAD reactions. The alpha-bromo ketone 19 was synthesized from protected mycosamine and employed in an intermolecular S(N)2 glycosylation reaction. Both routes were successful for the model alcohol, cholesterol.