Synthesis, structure and structure-activity relationship analysis of 3-tert-butoxycarbonyl-2-arylthiazolidine-4-carboxylic acid derivatives as potential antibacterial agents.

Nine 2-arylthiazolidine-4-carboxylic acid derivatives and nine 3-tert-butoxycarbonyl-2-arylthiazolidine-4-carboxylic acid derivatives were synthesized to screen for their antibacterial activities. Compounds 5, 14-18 were first reported. Their chemical structures were clearly determined by (1)H NMR, (13)C NMR, ESI mass spectra and elemental analyses, coupled with one selected single-crystal structure. All the compounds were assayed for antibacterial activities against two Gram-positive bacterial strains (Bacillus subtilis ATCC 6633 and Staphylococcus aureus ATCC 6538) and two Gram-negative bacterial strains (Escherichia coli ATCC 35218 and Pseudomonas aeruginosa ATCC 13525) by MTT method. Most of the 3-tert-butoxycarbonyl-2-arylthiazolidine-4-carboxylic acid derivatives exhibited better antibacterial activities against the four bacterial strains than relative 2-arylthiazolidine-4-carboxylic acid derivatives. Compound (2RS,4R)-3-(tert-butoxycarbonyl)-2-(5-fluoro-2-hydroxyphenyl)thiazolidine-4-carboxylic acid (14) showed powerful antibacterial activities against P. aeruginosa with IC(50) value of 0.195 microg/mL, which was superior to the positive controls Penicillin G and Kanamycin B, respectively. On the basis of the biological results, structure-activity relationships were discussed.