Apenem is a type ofβ-lactam with anunsaturated five-memberheterocycle containing asulfur atom in a pentacyclic ring fused to the β-lactam ring. Penems do not occur naturally; all are synthetic.[1] Related to penems arecarbapenems, which have a carbon atom in place of the sulfur atom.[2]
Faropenem, a penem. A sulfur atom and a double bond are present in the pentacyclic ring.[4]Imipenem, acarbapenem. Imipenem has a sulfur atom that is not in the pentacyclic ring.Benzylpenicillin, apenicillin. The double bond is absent in the pentacyclic ring.
Penem molecules do not occur naturally, and production of penems is an entirely synthetic process.
Five main penem subgroups — thiopenems, oxypenems, aminopenems, alkylpenems, and arylpenems — have been produced and are distinguished by the side chain (at position 2) of the unsaturated five-membered ring. One structurally distinct penem is BRL 42715. This molecule has no substitution at the above position, but has a bulky group attached to the β-lactam ring, and it displays effective inhibition of class Cβ-lactamases, but no antimicrobial activity.
One possible consequence of these structural differences of penems from other β-lactams may be reduced immunogenicity and immunogenic cross-reactivity.
^Schurek, Kristen N.; Wiebe, Ryan; Karlowsky, James A.; Rubinstein, Ethan; Hoban, Daryl J.; Zhanel, George G. (2007). "Faropenem: Review of a new oral penem".Expert Review of Anti-Infective Therapy.5 (2):185–198.doi:10.1586/14787210.5.2.185.PMID17402834.
