The Orthoester Glycosylation Method. Variations in the Anomeric Composition of the Product with Aglycone Basicity in the Two-Step Procedure.

Abstract

The previously obsd. influence (1976) of aglycone basicity on the steric outcome of the 2-step orthoester glycosylation procedure is further substantiated by the observation that 2-nitroethanol yields anomeric D-glucopyranosides in an α:β ratio of 44:56. Fluoroethanol yields the β-D-glucopyranoside only, ascribed to the gauche effect. A comparison of the products of glycosylation of cyclohexanol and 2,2,6,6-tetramethylcyclohexanol shows that steric hindrance may inhibit catalysis by electrophilic attack at the alkoxyl group, leading to an increase in the α-D-glucopyranoside produced. [on SciFinder(R)]