In 1976, fermentation broths obtained from the soil bacterium Streptomyces cattleya were found to be active in a screen for inhibitors of peptidoglycan biosynthesis.  Initial attempts to isolate the active compound proved difficult due to its chemical instability.  After many attempts and extensive purification, the material was finally isolated in >90% purity, allowing for the structural elucidation of thienamycin in 1979.
Thienamycin was the first among the naturally occurring class of carbapenem antibiotics to be discovered and isolated.  Carbapenems are similar in structure to their antibiotic “cousins” the penicillins.  Like penicillins, carbapenems contain a β-lactam ring (cyclic amide) fused to a five-membered ring.  Carbapenems differ in structure from penicillins in that within the five-membered ring a sulfur is replaced by a carbon atom (C1) and an unsaturation is present between C2 and C3 in the five-membered ring.