Research Article Novel 4-Thiazolidinone Derivatives as Anti-Infective Agents: Synthesis, Characterization, and Antimicrobial Evaluation Amit Gupta, Rajendra Singh, Pankaj K. Sonar, and Shailendra K. Saraf Faculty of Pharmacy, Babu Banarasi Das Northern India Institute of Technology, Sector-II, Dr. Akhilesh Das Nagar, Faizabad Road, Lucknow, Uttar Pradesh 227105, India Correspondence should be addressed to Shailendra K. Saraf; dirpharmniec@gmail.com Received 30 November 2015; Revised 7 January 2016; Accepted 12 January 2016 Academic Editor: Paul W. Huber Copyright © 2016 Amit Gupta et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. A series of new 4-thiazolidinone derivatives was synthesized, characterized by spectral techniques, and screened for antimicrobial activity. All the compounds were evaluated against fve Gram-positive bacteria, two Gram-negative bacteria, and two fungi, at concentrations of 50, 100, 200, 400, 800, and 1600 g/mL, respectively. Minimum inhibitory concentrations of all the compounds were also determined and were found to be in the range of 100–400 g/mL. All the compounds showed moderate-to-good antimicrobial activity. Compounds 4a [2-(4-fuoro-phenyl)-3-(4-methyl-5,6,7,8-tetrahydro-quinazolin-2-yl)-thiazolidin-4-one] and 4e [3-(4,6-dimethyl-pyrimidin-2-yl)-2-(2-methoxy-phenyl)-thiazolidin-4-one] were the most potent compounds of the series, exhibiting marked antimicrobial activity against Pseudomonas fuorescens, Staphylococcus aureus, and the fungal strains. Tus, on the basis of results obtained, it may be concluded that synthesized compounds exhibit a broad spectrum of antimicrobial activity. 1. Introduction Infections caused by microbes are among the leading causes of death worldwide. Te availability of limited number of antibiotics for the treatment of infections, and continuous development of resistance to the recently used antimicrobial agents, pose a serious challenge [1]. Tus, the discovery of innovative and potent antimicrobial agents may be the only way to resolve the resistance problem and develop successful remedy for the treatment of infectious diseases. 4-Tiazolidinones have recently been reported to be novel inhibitors of the bacterial enzyme Mur B (a precursor during the biosynthesis of peptidoglycan) and also to block some pathogenic mechanisms of bacteria [2]. 4-Tiazolidinones are derivatives of thiazolidine with a carbonyl group at the fourth position. Tis is a core structure in various synthetic pharmaceuticals displaying a broad spectrum of biological activities such as antimycobacterial [3–5], antimi- crobial [6–19], anticancer [20, 21], anticonvulsant [22–32], anti-infammatory and analgesic [33–37], antiparasitic [38– 43], antiviral and anti-HIV [44–49], antidiabetic [50–52], antihypertensive [53–55], antihyperlipidemic [56–58], and MAO inhibitors [59]. Te substituted thiazolidine moiety has attracted considerable interest in the development of biologically active compounds. In the present study, novel arylidene substituted 4-thiazolidinones were synthesized and evaluated as antimicrobial agents from heterocyclic scafold. 2. Materials and Methods All the chemicals and solvents used in the study were procured from S. D. Fine-Chem. Ltd., Mumbai, and Sigma- Aldrich Chemie, Germany. Culture media for antimicro- bial screening were procured from HiMedia Laboratories, Mumbai. Te standard microbial strains were procured from Microbial Type Culture Collection (MTCC), Institute of Microbial Technology, Chandigarh, India. Spectral studies (IR, NMR, and mass spectrometry, Table 1) of the synthesized compounds were performed at Central Drug Research Insti- tute, Lucknow. 2.1. Chemistry. 4-Tiazolidinones were synthesized in two steps. In the frst step, 2-aminopyrimidine derivatives were synthesized by the reaction of 1,3-dicarbonyl compounds with guanidine. Final compounds (4a–4f ) were synthesized Hindawi Publishing Corporation Biochemistry Research International Volume 2016, Article ID 8086762, 8 pages http://dx.doi.org/10.1155/2016/8086762