An Efficient Synthesis of β-<i>C</i>-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 Et<sub>3</sub>SiH/TMSOTf proceeded with complete stereoselectivity to produce the corresponding β-<i>C</i>-glycosides when the substrates were conformationally restricted in the <sup>4</sup>C<sub>1</sub>-chair form by a 3,4-<i>O</i>-cyclic diketal or a 4,6-<i>O</i>-benzylidene protecting group. Thus, the efficient construction of β-<i>C</i>-glycosides was achieved on the basis of the conformation restriction strategy.