Penams are the primary skeleton structures that define the penicillin subclass of the broader β-lactam family of antibiotics and related compounds. They are bicyclic ring systems containing a β-lactam moiety fused with a five-member thiazolidine ring.[1] Due to ring strain and limitations on amide resonance, the structure is unstable and highly susceptible to catalytic cleavage at the amide bond.[2] is the natural product parent that contains the penam structure. The β-lactam ring is in salmon. See also Penam.
