Penicillins structure consists of a side chain (a benzyl group and an amide
carbonyl) and a 6-Aminopenicillanic acid nucleus (a b-Lactam
ring and a Thiazolidone ring). The b-Lactam
ring is not found in any other natural product and is highly strained and thus
readily hydrolyzed, this makes penicillin very reactive towards acid and alkali
conditions. The diagram shows penicillin G or benzylpenicillin because of the
benzyl side chain. Yet penicillin's can differ by the changing of the side chain
which is attached to the amide carbonyl.
3D model of penicillin