NEW SPIRO DERIVATIVES OF PENICILLIN

Article abstract of DOI:10.1016/S0040-4039(01)82055-4

The first example of carbenoid ring expansion of thiophene to a 2H-thiopyran has been observed in its Rh-catalysed reaction with benzhydryl 6-diazopenicillinate.Buchner ring expansion of anisole with the same carbenoid gives two isomeric methoxy-cycloheptatrienes by attact on the upper face of the β-lactam ring.In one of the isomers, the methoxyl group shows a strong conformational preference in solution, revealed by n.O.e. difference spectroscopy.