mycin, N-acetylthienamycin and N-acetyldehydrothienamycin from S. cattleya7) and also a group of antibiotics, the epithienamycins A - D from S. flavogriseus.8,9) The olivanic acid derivatives

Streptomyces olivaceus ATCC 31365 produces a family of novel 1S-lactam antibiotics collectively referred to as the olivanic acids. Seven such compounds, MM 4550, MM 13902, MM 17880, MM 22380, MM 22381, MM 22382 and MM 22383 have been identified which have the same carbapenem nucleus but with different side chains attached to the nucleus. The compounds with an (8S) hydroxyethyl substituent and cis-orientated ~-lactam protons, MM 22380 and MM 22382, and their sulphate esters, MM 17880 and MM 13902, are potent antibiotics with MIC values against Gram-positive and Gram-negative bacteria in the range 0.1 3.1 tag,/ml. The corresponding (8S) hydroxyethyl compounds with trans-Q-lactam protons, MM 22381 and MM 22383, also have broad-spectrum activity but are rather less potent than the cis-compound. In addition to their antibiotic activity, the olivanic acids inhibit a number of S-lactamases and enhance the activity of 1I-lactams such as amoxycillin against (3-lactamase-producing bacteria. Significant differences are observed both in antibacterial activities and in 11-lactamase inhibition properties when the olivanic acids are compared with the related thienamycin antibiotics which have (8R) rather than (8S) stereochemistry and trans-jS-lactam protons.