Microbial transformation of 6-O-methylerythromycin derivatives.

Mucor circinelloides f. griseo-cyanus IFO 4563 was found to convert 6-O-methylerythromycin A (TE-031, A-56268) to (14R)-14-hydroxy-6-O-methylerythromycin A [14R)-14-hydroxy TE-031). The TLC and spectral data of the conversion product were perfectly identical with those of an active major metabolite of TE-031 in humans (M-5). A related antibiotic, 6-O-methylerythromycin B (TB-010), was able to be similarly transformed to its C-14 hydroxy analogue [14R)-14-hydroxy-6-O-methylerythromycin B, (14R)-14-hydroxy TB-010). The MICs of (14R)-14-hydroxy-6-O-methylerythromycin B against some Gram-positive bacteria were almost equal to those of 6-O-methylerythromycin B. It is suggested that the hydroxylation at C-14 of 6-O-methylerythromycins A and B scarcely reduces their in vitro activity.