An efficient synthesis of beta-C-glycosides based on the conformational restriction strategy: Lewis acid promoted silane reduction of the anomeric position with complete stereoselectivity.

[reaction: see text] The reduction of glyconolactols having an anomeric carbon substituent by Et(3)SiH/TMSOTf proceeded with complete stereoselectivity to produce the corresponding beta-C-glycosides when the substrates were conformationally restricted in the (4)C(1)-chair form by a 3,4-O-cyclic diketal or a 4,6-O-benzylidene protecting group. Thus, the efficient construction of beta-C-glycosides was achieved on the basis of the conformation restriction strategy.