The allyl group for protection in carbohydrate chemistry. Part 20. Synthesis of 1L-1-O-methyl-myo-inositol [(+)-bornesitol] by resolution of (±)-1,2,4-tri-O-benzyl-myo-inositol

Abstract

Racemic 1,2,4-tri-O-benzyl-myo-inositol was prepared by two new routes from (±)-1,4-di-O-benzyl-5,6-O-isopropylidene-myo-inositol, one route involving the crystalline intermediate (±)-1-O-allyl-3,6-di-O-benzyl-4,5-O-isopropylidene-myo-inositol. Oxidation of the latter and (±)-1,2,4-tri-O-benzyl-5,6-O-isopropylidene-myo-inositol with acetic anhydride-dimethyl sulphoxide gave the corresponding ketones, which were reduced with sodium borohydride to give the starting alcohols in good yield, thus providing suitable routes for the synthesis of isotopically labelled material. Racemic 1,2,4-tri-O-benzyl-5,6-O-isopropylidene-myo-inositol was resolved using (–)-ω-camphanic acid chloride to give, readily and in high yield (86%), the ω-camphanate of 1D-1,2,4-tri-O-benzyl-5,6-O-isopropylidene-myoinositol, which was converted into 1L-1-O-methyl-myo-inositol [(+)-bornesitol] and 1D-1,2,4,5,6-penta-O-benzyl-myo-inositol which had previously been obtained by hydrolysis of perbenzylated galactinol.