3-SUBSTITUERAD-TIOMETYL-3-CEFEM-4-KARBOXYLSYRADERIVAT OCH FORFARANDE FOR FRAMSTELLNING DERAV

摘要

Starting from novel cephalosporin derivatives of the formula in which R represents a heterocyclic radical optionally carrying several substituents and A represents one of the groups in which groups R1 and R2 represent hydrogen or lower alkyl or aryl radicals which can have one or more substituents, X represents oxygen or sulphur and R3 represents a lower alkyl radical, corresponding 7-aminocephemcarboxylic acids can be prepared in high yield by reacting a compound of the formula I with a silylating agent and then treating the reaction product first with an iminohalide-forming agent and then with an iminoether-forming reagent, after which the reaction mixture is subjected to a hydrolysis. The N-unsubstituted 7-aminocephemcarboxylic acid compounds thus obtained carrying the radical R-S-CH2- in position 3 are important intermediates in the synthesis of cephalosporin antibiotics.