abstract |
Useful intermediates, 7α-acylamino-3-(oxo or exomethylene)-1-dethia-1-oxacepham-4α-carboxylates, are produced by the intramolecular carbenoid insertion of a 2-diazo-3-(oxo or exomethylene)-4-(3α-acylamino-2-oxoazetidin-4β-yl)oxybutyrate prepared in several steps from the corresponding oxazolinoazetidinone and diketone. |