Semisynthetic β-Rhodomycins: A New Approach to the Synthesis of 4-O-Methyl-β-Rhodomycins

Syntheses of 4-O-methyl-β-rhodomycins are described. Glycosylation (trimethylsilyl triflate, dichloromethane-acetone 10:1, -30 °C) of 4-O-methyl-10-O-p-nitrobenzoyl-β-rhodomycinone, obtained from β-rhodomycinone (βRMN) in a 6-step synthesis, with 1-O-tert-butyl(dimethyl)silylated derivatives of 4-O-acetyl- or 4-O-p-nitrobenzoyl-2,3,6-tri-deoxy-3-trifluoroacetylamino-β-L-arabino- and lyxo-hexopyranoses or 2,6-di-O-acetyl-2,6-dideoxy-β-L-lyxo-hexopyranose afforded 7-O-α-L-glycosyl-β-rhodomycinones. Removal of the O- and N-acyl groups with 0.1M and 1M NaOH gave the 7-O-(3-amino-2,3,6-trideoxy-α-L-arabino- and lyxo-hexopyranosyl)-4-O-methyl-β-rhodomycinones and 7-O-(2,6-dideoxy-α-L-lyxo-hexopyranosyl)-4-O-methyl-β-rhodomycinone.