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.