In the course of screening for anti-enterococcal antibiotics from microbial resources, a new tirandamycin congener (1), together with four known tirandamycins (2 to 5), were isolated from Streptomyces tirandamycinicus TMPU-20A040. The structures of these tirandamycins were elucidated using NMR and MS analyses
1 was identified as 12-carboxy tirandamycin A and 2 to 5 as known tirandamycins A (2), B (3), E (4), and J (5). Compounds 1 to 3 exhibited selective anti-Enterococci activity, including vancomycin-resistant strains, with MIC in the range of 1.0 to 64 µg ml