Novel Analogues of Sydnone: Synthesis, Characterization and Antibacterial Evaluation

New sydnone derivatives bearing a substituted phenyl ring at the 3‐position have been synthesized. Two separate series of 3‐(carboxyphenyl)sydnone derivatives have been prepared by cyclization of the corresponding N ‐nitroso‐ N ‐(carboxyphenyl)‐glycine 3 . The obtained 3‐(carboxyphenyl)sydnones 4 were subjected to a series of different chemical reactions on the carboxylic acid group. Compound 5 , the potassium salt of 4a , was reacted with α‐chloroacetanilide derivatives 6 to give the corresponding esters 7 . On the other hand, the acid hydrazide 9 was condensed with different aromatic aldehydes to give the corresponding arylidene derivatives 10 . The synthesized compounds were tested for their antibacterial activities against both gram‐positive and gram‐negative organisms. Some of the test compounds exhibited high activity; among them, 10d is considered to be a lead compound possessing high broad‐spectrum antibacterial activity.