Microbial transformation of maridomycin III by Serratia marcescens

Two transformation products of maridomycin (MDM) III, MDM-S1 and MDM-S2 named after Serratia marcescens, were isolated by silica gel chromatography. NMR and IR analysis revealed that MDM-S1 and -S2 had no aldehyde group at C-18 on the macrolactone ring, and that the hydroxyl group at C-9 seemed to disappear. Although MDM-S1 and -S2 are less active against Gram-positive bacteria than starting MDM III they are interesting materials in view of the introduction of nitrogen into each molecule, and that the transformation products are produced by Gram-negative bacteria which are thought to be insensitive to macrolide antibiotics.