Asymmetric Synthesis of the Main Pyridine Skeleton for a Macrobicyclic Antibiotic, Cyclothiazomycin

Stoichiometric asymmetric reduction of the ketone group of a 2-acetyl-3,6-disubstituted pyridine derivative with an oxazaborolidine and N-ethyl-N-isopropyl anilineborane complex gave the corresponding (S)-lactone derivative 5 in 96% ee almost quantitatively. Hydrogenolytic cleavage of 5 gave the expected (S)-2-(1hydroxyethyl)pyridine derivative