Metal-catalyzed and -promoted cyclizations for the synthesis of cephalosporins: A possible DAOC/ DAC synthetase biomimetic process

Article abstract of DOI:10.1016/S0040-4020(01)80427-0

A thiyl radical cyclization approach to the sulphur containing ring of cephams is described. The reaction was carried out using metals able to perform a single-electron oxidation process under stoichiometric [Fe(III), MN(OAc)₃] or catalytic [Fe(III)] conditions. Furthermore, the FeCl₃ or Mn (OAc)₃/LiX promoted reactions afforded, by a double single-electron oxidation process, over oxidized compounds. The relationship with the mechanistic hypothesis proposed by Baldwin for the DAOC/DACS-catalyzed ring expansion from Penicillin N to Desacetoxy cephalosporin C is discussed.