A synthesis of l-ristosamine and a derivative of its C-4 epimer

A synthesis of l-ristosamine from l-rhamnal is described, involving the sequence of reactions: methoxymercuration, tosylation, azide displacement, and reduction, which gave methyl α-l-ristosaminide (10). Acid hydrolysis then afforded l-ristosamine hydrochloride. Trifluoroacetylation of the hydrochloride of 10 followed by saponification and oxidation with ruthenium tetraoxide gave methyl 2,3,6-tri-deoxy-3-trifluoroacetamido-α-l-erythro-hexopyranosid-4-ulose (17). Borohydride reduction of 17 gave a separable, 1:1 mixture of methyl 2,3,6-trideoxy-3-trifluoroacetamido-α-l-ribo- and α-l-xylo-hexopyranoside.