RELATIVE REACTIVITIES OF HYDROXYL GROUPS IN CARBOHYDRATE DERIVATIVES . SPECIFIC NUCLEAR MAGNETIC RESONANCE SPECTRAL ASSIGNMENTS OF ACETYL GROUPS IN METHYL DELTA-D-GLUCOPYRANOSIDE TETRAACETATE AND RELATED DERIVATIVES

Methyl α-D-glucopyranoside tetraacetates (1) having a trideuterioacetyl group at C-2 (1a), C-3 (1b), C-4 (1c), and C-6 (1d) were synthesized by the unambiguous routes shown in Scheme I to permit assignment of each individual acetoxy-group signal in the nmr spectrum of 1. The 6-acetoxy group resonates at lower field than the other acetoxy groups in chloroform-d, pyridine-d5, and benzene-d6 (where its signal coincides with that of the 3-acetoxy group). In pyridine-d5 and benzene-d6 the highest field signal is that of the 2-acetoxy group, but in chloroform-d it is that of the 3-acetoxy group. The acetoxy-group signals in methyl 2,3-di-0-acetyl-4,6-0-benzylidene-α-D-glucopyranoside (6) were assigned similarly by synthesis of the 2-trideuterioacetyl (6a) and 3-trideuterioacetyl (6b) analogs. It was shown that acetyl groups in 1 do not exchange with the reagent under the normal conditions for acetylation with acetic anhydride-pyridine. The relative extents of acetylation of the various hydroxyl positions, when methyl α-D-glucopyranoside and its 4,6-benzylidene acetal were treated with a limited proportion of acetic anhydride in pyridine, were determined. © 1969, American Chemical Society. All rights reserved.