Cephalosporins to carbapenems: 1-oxygenated carbapenems and carbapenams.

The photo "Wolff" rearrangement of readily available 2-diazoceph-3-em oxides (1) directly affords carbapen-2-ems, allowing a facile entry into a ring system previously accessible only by total synthesis, lengthly semisynthesis or fermentation. The chirality of the cephalosporin is accurately translated into the corresponding carbapenem. The resulting 1-oxocarbapenems (2) were selectively transformed through reduction into 1-oxygenated carbapenems and carbapenams (3 and 4, respectively). On microbiological screening, a carbapenem (3c) was found to possess a broad spectrum of activity. An interesting antibacterial profile was discovered for a carbapenam (26).