Synthesis and antimicrobial activities of some new tetrahydro-2H-1,3,5-thiadiazine-2-thione derivatives of cephalexin.

In this study, compounds with a 7-[2-(dihydro-5-substituted 6-thioxo-2H-1,3,5-thiadiazine-3[4H]-yl)-2-phenyl]acetamido-3 -methyl-3- cephem-4-carboxylic acid structure were synthesized by reacting cephalexin monohydrate with formaldehyde and dithiocarbamic acid salts prepared from some primary amines. The structure of the compounds was confirmed by spectral data and elementary analysis. The antimicrobial activities of the compounds were investigated against some bacteria (Staphylococcus aureus, Streptococcus faecalis, Escherichia coli and Pseudomonas aeruginosa) and some Candida sp. (C. albicans, C. parapsilosis, C. stellatoidea and C. pseudotropicalis) by using tube dilution method. In microbiological studies, cephalexin monohydrate was used as reference standard. Both compounds were synthesized and cephalexin monohydrate was found ineffective against S. faecalis and P. aeruginosa in the concentrations studied. While most of the compounds showed bacteriostatic activity against S. aureus, compounds 1, 3 and 7 showed the same activity against E. coli. On the other hand, compound 3, 5, 6, 7 and 10 showed anticandidal activity, whereas cephalexin monohydrate was not active against any Candida sp. Compound 11 was found effective against C. stellatoidea and C. pseudotropicalis.