Versuche zur Totalsynthese von Cephalosporinderivaten, II 1) Substitutionsreaktionen an trans ‐3‐Sulfonyloxy‐2‐azetidinonen. – Eine Synthese von cis ‐3‐Acylamino‐4‐alkylthio‐2‐azetidinonen

trans ‐3‐Sulfonyloxy‐4‐alkylthio‐2‐azetidinone 1 reagieren mit Natriumazid in Dimethylsulfoxid unter Inversion zu cis ‐3‐Azido‐4‐alkylthio‐2‐azetidinonen 2 , die zu den Aminoverbindungen 4 reduziert werden können. Acylierung von 4 liefert die cis ‐3‐Acylamino‐4‐alkylthio‐2‐azetidinone 5 . Die Reaktion der Sulfonyloxygruppe mit weiteren Nucleophilen, wie Halogeniden, Thiocyanaten, Sauerstoffnucleophilen, Thioacetat und anderen wird beschrieben. Studies on the Total Synthesis of Cephalosporin Derivatives, II 1) . – Substitution Reactions with trans ‐3‐Sulfonyloxy‐2‐azetidinones. – A Synthesis of cis ‐3‐Acylamino‐4‐alkylthio‐2‐azetidinones cis ‐3‐Azido‐4‐alkylthio‐2‐azetidinones 2 are obtained by displacement of the sulfonyloxy group with inversion in trans ‐3‐sulfonyloxy‐4‐alkylthio‐2‐azetidinones 1 by the azide ion. Reduction of 2 yields the amino compounds 4 which are acylated to give cis ‐3‐acylamino‐ 4 ‐alkylthio‐2‐azetidinones 5 . The reaction of trans ‐3‐sulfonyloxy‐2‐azetidinones with other nucleophiles such as halides, thiocyanates, oxygen nucleophiles, and thioacetate is also described.