Chemical modification of maridomycin, a new macrolide antibiotic.

Maridomycin, a new macrolide antibiotic, and tetrahydromaridomycin were acylated into their mono, di, and tri acyl derivatives. These derivatives were compared with the parent antibiotic, maridomycin, for their (i) in vitro antimicrobial activities, (ii) protective effect in mice infected with Staphylococcus aureus (oral administration), (iii) blood levels attained in rats, and (iv) acute toxicity in mice (intraperitoneal administration). All the derivatives showed either the same or less activity in vitro, but 9-acyl, 9, 2'-diacylmaridomycin and 9, 13, 2'-triacetyltetrahydromaridomycin demonstrated improved therapeutic effects together with higher blood levels and low toxicity. 9-Propionylmaridomycin showed the most favorable biological properties.