Solid-state 13C NMR, X-ray diffraction and structural study of methyl 4-O-methyl β-D-glucopyranosides with all eight possible methyl-substitution patterns

Abstract

Cellulose model compounds that mimic the building blocks of modified cellulose and cellulose derivatives are widely used in cellulose research to infer the properties of the polymer from the monomer. Based on the well-established model compound methyl 4-O-methyl β-d-glucopyranoside, in which the methyl groups represent the truncated side chains of the cellulose, the corresponding O-methyl-substituted derivatives with all eight different substitution patterns (mono-, di- and trisubstituted at O-2, O-3, O-6) were synthesized. Crystallization of the products in sufficient quality for solid-state structure determination by single-crystal X-ray diffraction succeeded in all cases, and the results are reported. Two of the compounds showed more than one independent molecule per unit cell. Solid-state 13C NMR showed a significant down-field shift (5–10 ppm) of the OMe-substituted carbons relative to the OH-substituted counterparts and generally confirmed the important influence of solid-state packing on the chemical shifts as seen by comparison to the solution NMR data.Graphical abstract