An Efficient Synthesis of β-C-Glycosides Based on the Conformational Restriction Strategy:  Lewis Acid Promoted Silane Reduction of the Anomeric Position with Complete Stereoselectivity

The reduction of glyconolactols having an anomeric carbon substituent by Et3SiH/TMSOTf proceeded with complete stereoselectivity to produce the corresponding β-C-glycosides when the substrates were conformationally restricted in the 4C1-chair form by a 3,4-O-cyclic diketal or a 4,6-O-benzylidene protecting group. Thus, the efficient construction of β-C-glycosides was achieved on the basis of the conformation restriction strategy.