Alkyl–oxygen versus glycosyl–oxygen fission in the acid-catalysed hydrolyses of some alkyl β-D-glycopyranosides

Abstract

The rates of hydrolysis of 1-adamantyl β-D-glucopyranoside, and of t-butyl, 1,1-diethylpropyl, and diphenylmethyl β-D-galactopyranosides in 0·500M-aqueous sulphuric acid indicate steric acceleration is the major driving force for the accelerated rates of hydrolysis of tertiary glycopyranosides: generation of planar tertiary cations is, however, predominant in the gluco-series and important in the galacto-series. Product-analytical studies and the rate of acetolysis of 2,4-dinitrophenyl β-D-galactopyranoside relative to those of the dinitrophenolates of the aglycons confirm this.