Penem
![Faropenem, a penem. Note sulfur and double bond in ring.](/Images/godic/202502/01/Faropenem.svg1211.png")
![Imipenem, a carbapenem. Although imipenem has a sulfur, the sulfur is not in the ring.](/Images/godic/202502/01/Imipenem.svg1211.png")
![Benzylpenicillin, a Penicllin. Note the absence of the double bond in the ring.](/Images/godic/202502/01/Penicillin-G1212.png")
A penem is a type of unsaturated β-lactam.
An example is faropenem.
Penems are similar in structure to carbapenems. However, where penems have a sulfur, carbapenems have another carbon.
There are no known naturally occurring penems; all of them are synthetically made.