Synthesis and nuclear magnetic resonance spectra of some partially acylated β-D-glucopyranosides

Abstract

The synthesis of ten new partially acylated derivatives of methyl β-D-glucopyranoside, all with an acyl group at C-6, is described. The nuclear magnetic resonance spectra of these compounds, and of a number of related derivatives, have been measured using pyridine, acetone-d₆, and deuteriochloroform as solvents. When OH-4 is acylated, the H-6 signals are at higher field (by 0.1–0.3 p.p.m.) than when OH-4 is not acylated, but this effect is not observed when OH-3 is acylated. When a trimethylsilyl ether group is introduced at C-4 the difference between the chemical shifts of the H-6 protons (δA –δB) increases markedly. Estimation of J_BX and J_AX (where B is the H-6 proton at higher field and X is H-5), from spectra obtained using acetone-d₆ and pyridine as solvents, shows that J_BX < J_AX when there is an acyl group at C-4 but J_BX > J_AX when there is no acyl group at C-4.