Isomeric penam and cepham compounds have been prepared and isolated. I t has been established that a thiiranium ion is a common intermediate in the interconversions of penam and cepham systems. The mechanism and stereochemistry of these interconversions have been studied in detail. A new synthesis of deacetoxycephalosporin starting from substituted penams and cephams is reported

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2-Hydroxy-6-methoxy-1,2,3,4-tetrahydro-2-naphthoic acid and its 8- methoxy isomer were converted into trichloroacetate and dichloroacetate derivatives and thence to diazoketones (2), (3), (12) and (13). The acid-catalysed cyclization of these substrates to the dienones (6), (7), (16) and (17), respectively, was then studied. The trichloroacetoxy derivatives gave the best yields of dienones.

Die Penicillinsulfoxide (I) werden von Halogenierungsreagenzien unter Bildung der Sulfinylchloride (II) (am S mögliche epimere Formen) aufgespalten.