14-Hydroxy-6-O-methylerythromycins A, active metabolites of 6-O-methylerythromycin A in human

(14R)-14-Hydroxy-6-O-methylerythromycin A and (14S)-epimer have been isolated as active metabolites from human urine after oral administration of 6-O-methylerythromycin A (TE-031, A-56268). The structures of these metabolites were determined by means of mass, 1H and 13C NMR spectroscopies. Antimicrobial activities of (14R)-14-hydroxy-6-O-methylerythromycin A, a major metabolite, were comparable to those of the parent drug TE-031, whereas (14S)-14-hydroxy-6-O-methylerythromycin A was 4- to 8-fold less active than TE-031 against bacterial standard strains.