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

Compounds having alpha-[dihydro-5-substituted 6-thioxo-2H- 1,3,5-thiadiazine-3(4H)-yl]benzylpenicillin structure were synthesized by the reaction of ampicillin trihydrate, formaldehyde and dithiocarbamic acid salts. The structures were evident from chemical and spectral analysis. The antimicrobial activities of the compounds were investigated against some gram-positive (Staphylococcus aureus and Streptococcus faecalis) and gram-negative (Escherichia coli and Pseudomonas aeruginosa) bacteria and some yeast-like fungi (Candida albicans, C. parapsilosis, C. stellatoidea and C. pseudotropicalis) and molds such as Trichophyton rubrum, T. mentagrophytes, Microsporum canis, M. gypseum, Penicillium and Aspergillus by the tube dilution method. In addition to MIC (minimal inhibitory concentration), MBC (minimal bactericidal concentration) and MFC (minimal fungicidal concentration) values were determined using ampicillin trihydrate as standard. The compounds synthesized were usually found as effective as ampicillin trihydrate against S. aureus and S. faecalis and less effective than ampicillin trihydrate against E. coli. Both the compounds synthesized and ampicillin trihydrate are ineffective in the concentrations studied against P. aeruginosa. Compound 10 and 11 are more effective against all the yeast-like fungi than the other compounds and ampicillin trihydrate.