Synthetic Approach to <i>exo</i>-Glycals from 1-<i>C</i>-Vinyl-<scp>d</scp>-glycopyranose Derivatives via an S_N1′-Substitution Mechanism

Abstract

This paper describes a novel synthetic approach to exo-glycals from 1-C-vinyl-d-glycopyranose derivatives via the SN1′-type substitution mechanism. The reaction of the 2,3,4,6-tetra-O-benzyl-1-C-vinyl-α-d-glycopyranose derivatives with several tri­methylsilylated nucleophiles was investigated. The reactions in dichloromethane-acetonitrile (1:1) at -78 °C in the presence of 20 mol% trimethylsilyl trifluoromethanesulfonate using allyltrimethylsilane and silyl enol ethers as the nucleophiles stereoselectively afforded the Z-exo-glycal derivatives in good yields.