Synthesis, Characterization, and Antimicrobial Evaluation of Some Novel 3′-(6-(Substituted Phenyl)-4-Phenyl-6H-1,3-Thiazine-2-yl)Spiro[Indoline-3,3′-Isothiazolidine]-2,4′-Dione Derivatives

Thiazolidinediones (TZDs) are the vital component of a number of pharmaceuticals and biologically active compounds. Owing to the diversified pharmaceutical applications of TZD derivatives, we conceived a new synthetic approach for the preparation of a series of spiro-thiazolidinediones by the reaction of synthesized TZDs with thioglycolic acid. Melting point and thin-layer chromatography ascertained the purity of the synthesized compounds. Elemental analysis, FTIR, 1H and 13C NMR spectral studies have been used for the characterization of the synthesized compounds. The synthesized chalcones, thiazine, TZDs, and spiro-thiazolidinediones are in accordance with the standard values of different spectral techniques. The appearance of a sharp singlet of two protons of CH2 at 2.5 - 3.0 ppm in 1H NMR of spiro-thiazolidinediones, which was absent in TZDs, suggests the formation of a spiro ring. All the novel compounds were screened for their antimicrobial activity on Gram-negative (P. aeruginosa, E. coli) and Gram-positive (B. subtilis, S. aureus) bacteria. The final synthesized compounds exhibited excellent to good responses against the tested microbes. The change of the substituent and its position plays a significant role in the activity of the synthesized spiro-thiazolidinediones.