New cirramycin-family antibiotics F-1 and F-2. Selection of producer mutants, fermentation, isolation, structural elucidation and antibacterial activity.

Two new 16-membered macrolides, cirramycins F-1 and F-2, were isolated from the culture filtrate of a mutant strain B-1425 of Streptomyces cirratus JTB-3. The antibiotics were also produced by bio-transformation of cirramycin A1 using a blocked mutant strain A-0033. Structures of F-1 and F-2 have been elucidated by spectral interpretation and analysis of acid degradation products. Both involved isomeric modification of a neutral sugar; F-1 contained L-rhodinose, and F-2 L-amicetose. Based on spectral data, cirramycin F-1 and antibiotic A6888C were found to be identical. Cirramycins F-1 and F-2 are active against Gram-positive bacteria, but less active than cirramycin A1.