beta-lactams (including polycyclic) derived from chromium carbenes

The photolytic reaction of N-methylbenzylideneimine with 12-methoxypodocarp ane chromium carbenes gave products derived either from carbon monoxide dis sociation followed by 12-methoxy ligation or from oxidation of the carbene metal moiety, while the reaction of N-methylbenzylideneimine with 12-desmet hoxy diterpenoid carbenes gave diterpenoid beta -lactams. The relative ster eochemistry of two monocyclic 3,4-diaryl beta -lactams prepared from a meth oxy- or ethylthio-phenylcarbene by photolysis with an imine has been determ ined by X-ray crystallography. (C) 2001 Elsevier Science B.V. All rights re served.