Penem Explained

Penem should not be confused with penam.

A penem is a type of β-lactam with an unsaturated five-member heterocycle containing a sulfur atom in a pentacyclic ring fused to the β-lactam ring. Penems do not occur naturally; all are synthetic.^[1] Related to penems are carbapenems, which have a carbon atom in place of the sulfur atom.^[2]

An example is faropenem.^[3]

Structure

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 C β-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.

Further reading

• Sasaki A, Goda K, Enomoto M, Sunagawa M . Synthetic studies of carbapenem and penem antibiotics. II. Synthesis of 3-acetyl-2-azetidinones by (2 + 2) cycloaddition of diketene and Schiff bases . Chemical & Pharmaceutical Bulletin . 40 . 5 . 1094–7 . May 1992 . 1394625 . 10.1248/cpb.40.1094. free .

Notes and References

1. Antimicrobic Newsletter. The carbapenems and Penem Antibiotics—a brief review. Richard Wise. 7. 10. 1990. 73–78. 10.1016/0738-1751(90)90045-E.
2. Web site: Medscape.com .
3. Milazzo I, Blandino G, Caccamo F, Musumeci R, Nicoletti G, Speciale A . Faropenem, a new oral penem: antibacterial activity against selected anaerobic and fastidious periodontal isolates . . 51 . 3 . 721–5 . March 2003 . 12615878 . 10.1093/jac/dkg120. free .