Synthesis of (2R, 3S, 4S)-4-Amino-3-hydroxy-2-methyl-5-(3-pyridyl)pentanoic Acid Present in Antibiotic Pyridomycin

Natural (2R,3S,4S)-4-arnino-3-hydroxy-2-methyl-5-(3-pyridyl)pentanoic acid (1) present in antibiotic pyridomycin was synthesized. The 5,6-anhydro-1,2-O-isopropylidene-3-C-methyl-α-D-allofuranose (4) was prepared from (the known) 3-deoxy-1,2;5,6-di-O-isopropylidene-3-C-methyl-α-D-allofuranose (2). Regiospecific introduction of 3-pyridyl group to the C–6 of 4 was effected by 3-pyridyllithium. The product (5) was converted to the 5-azido derivative (7) by the SN2 substitution reaction of the 5-mesylate (6) of 5. Hydrolysis of 7 followed by two-stage oxidation with periodate-bromine in aqueous acetic acid afforded (2R,3S,4S)-4-azido-3-formyloxy-2-methyl-5-(3-pyridyl) pentanoic acid (9), which was transformed to the dihydrochloride of 1.