**1. Introduction**

Heterocyclic compounds play an important role in organic chemistry and of supreme practical and theoretical consequence. Therefore, more research being done on heterocyclic compound in chemistry. Heterocyclic compounds have an important role in therapeutic agents, drugs, dye stuffs etc. Therefore heterocyclic compound has taken a prominent place in the field of chemistry. Heterocyclic compounds retain the key to improve the quality of human life for example; more than 70% of the medications (or) drug used today is heterocyclic compounds. These are widely available in nature and act as key intermediates in biological processes. Over the years, chemists have paid close attention to a variety of physiologically active compounds that contain heteroatoms including nitrogen, sulphur, and oxygen because of their significance to biology. Thiazolidinone is considered as indispensable anchor for development of new therapeutic agents because this five member magic moiety possesses all types biological activities. Thus the thiazolidinone nucleus has been studied in the field of organic, medicinal and photochemistry. There are many examples of biologically active such as antibiofilm [1, 2], hypoglycemic [3], antimicrobial [4], analgesic [5], antipyretic [6] and anti-inflammatory activities [7, 8] anticonvulsant [9], antihistaminic [10], anti HIV [11] cardio protective [12], antinociceptive [13] With a sulphur atom at position 1, a nitrogen atom at position 3, and a carbonyl group at position 2, 4, or 5, thiazolidinones are thiazolidine derivatives. However, its derivatives are among the

most researched moieties, and the discovery of its existence in penicillin was the first indication that it existed in nature. Similar to 1,3-thiazolidin-4-ones, which are heterocyclic nuclei with a sulphur atom at position 1, a nitrogen atom at position 3, and a carbonyl group at position 4, they have been the focus of substantial research recently. Since it is so adaptable that the 4- thiazolidinone scaffold has been used in a number of clinically effective medications. They have been used anti-HIV, anti-tubercular, antimicrobial, anti-inflammatory and anti-viral medicines. The presence of arylazo, sulfamoylphenyl or phenylhydrazone moiety at various postions of the thiazolidone ring has been extensively reported to enhance anti-microbial activity. Its antibacterial activity may be caused by its inhibitory activity of enzyme Mur B, which is a precursor acting during the biosynthesis of peptidoglycan. Numerous publications highlighting their chemistry and pharmacological uses have been published in the literature. Thiazolidinone possess wide range of biological actions from antibacterial to anticancer. Various recent new drug developments of thiazolidinone derivatives show better effect and less toxicity. Moreover the possible improvements in the activity can be achieved by slight modifications in the substituent on the thiazolidinone nucleus. This has been noticed so far, that the introduction of another heterocyclic moiety into the thiazolidinone nuclei will enhance the biological activities.

Recently, thiazole and thiazolidinone derivative have been used as a potent antitrypanosomal agents [14]. Therfore in this chapter it is planned to discuss the synthesis of various thiazolidinone derivatives in brief and their widespectrum bilogical activities will be discussed elaborately.
