The synthesis of oxygen analogs of cepham. A new bicyclic system

The synthesis of a new bicyclic system has been reported. Three substituted 5,6‐dihydro‐1,3‐oxazines have been condensed to a fused β‐lactam ring system by use of phthaloylglycyl chloride. The resulting phthalimido compounds were dephthaloylated to the corresponding oxygen analogs of cepham (2).