Preparation of 1,2-O-isopropylidene derivatives of α-d-galactoseptanose, β-l-altroseptanose, and 3-O-methyl-α-d-guloseptanose Original Research Article

Displacement of the tosyloxy group in 5-O-benzyl-1,2-O-isopropylidene-4-O-(p-toluenesulfonyl)-α-d-glucoseptanose has yielded derivatives of 1,2-O-isopropylidene-α-d-galactoseptanose. Acid catalysed acetonation then gave 1,2:3,4-di-O-isopropylidene-α-d-galactoseptanose or 1,2;4,5-di-O-isopropylidene-α-d-galactoseptanose using lower acid concentrations. Reduction of the ketone derived from 1,2:3,4-O-isopropylidene-α-d-septanose gave 1,2;3,4-di-O-isopropylidene-β-l-altroseptanose. Reaction of 3,4-anhydro-5-O-benzyl-1,2-O-isopropylidene-α-d-galactoseptanose with sodium methoxide gave 5-O-benzyl-1,2-O-isopropylidene-4-O-methyl-α-d-glucoseptanose and 5-O-benzyl-1,2-O-isopropylidene-3-O-methyl-α-d-guloseptanose. Solution-state conformations of these compounds have been deduced from their 1H NMR spectra.