Convenient syntheses of L-digitoxose, L-cymarose, and L-ristosamine

Abstract

Methyl 2,3-O-benzylidene-6-deoxy-4-O-(2-methoxyethoxymethyl)-α-L-mannopyranoside (10) and the 4-O-(methoxymethyl) analogue (11) reacted with butyl-lithium to give the 4-O-substituted methyl 2,6-dideoxy-α-L-erythro- hexopyranosid-3-uloses (12) and (13), respectively. Appropriate transformations on these keto-sugars afforded practical syntheses of 2,6-dideoxy-L-ribo-hexopyranose (L-digitoxose)(15), its 3-O-methyl analogue (17)(L-cymarose), and 3-acetamido-2,3,6-trideoxy-L-ribo-hexose (N-acetyl-L-ristosamine).

A slight amendment to one of the sugar residues in published structures of the orthosomycin antibiotics flambamycin and avilamycins is indicated.