Synthesis of new branched-chain aminodeoxyhexoses related to daunosamine (3-amino-2,3,6-trideoxy-l-lyxo-hexose)

Addition of methylmagnesium iodide to methyl 2,3,6-trideoxy-3-trifluoro-acetamido-α-l-threo-hexopyranosid-4-ulose (3) gave methyl 2,3,6-trideoxy-4-C-methyl-3-trifluoroacetamido-α-l-lyxo-hexopyranoside (4) and its l-arabino analogue, depending upon the reaction temperature and the solvent. The corresponding 4-O-methyl derivatives were obtained by treatment of 4 and 5 with diazomethane in the presence of boron trifluoride etherate. Treatment of 4 with thionyl chloride, followed by an alkaline work-up, gave methyl, 2,3,4,6-tetradeoxy-4-C-methylene-3-trifluoro-acetamido-α-l-threo-hexopyranoside (8), which was stereoselectively reduced to methyl 2,3,4,6-tetradeoxy-4-C-methyl-3-trifluoroacetamido-α-l-arabino-hexopyranoside. Epoxidation of 8 with 3-chloroperoxybenzoic acid gave the corresponding 4,4₁-anhydro-4-C-hydroxymethyl-l-lyxo derivative (10), which was also prepared by treatment of 3 with diazomethane. Azidolysis of 10, followed by catalytic hydrogenation and N-trifluoroacetylation, gave methyl 2,3,6-trideoxy-3-trifuloroacetamido-4-C-trifluoroacetamidomethyl-α-l-lyxo-hexopyranoside.