Usha N. Jain

1,4-Benzothiazine derivatives having variable antifungal activity against four species of fungus such as Candida albicans, Trichophyton rubrum, Epidermophyton floccosum and Malassazia furfur  were selected to develop 2D and 3DQSAR models. The best 2DQSAR model was selected, having correlation coefficient r2 (0.8747) and cross validated squared correlation coefficient q2 (0.7145) with external predictive ability of pred_r2 (0.9658). 2DQSAR parameters are Quadrople1, SssCH2count, XA Average hydrophobicity, X Amost hydrophilic area and Polar surface area excluding P and S contributed in the model. The best 3DQSAR model having the correlation coefficient r2= 0.8635 was selected for further study. The model was further validated by means of crossed squared correlation coefficient q2 =0.7614 and pred_r2 =0.6654, which show that the model has good predictive ability and was developed by Forward SW-MLR. From QSAR model it concluded that the bulky substitution is require at para and meta position of Phenyl ring and less bulky substitution at ortho position of phenyl ring for antifungal activity.

A series of [Alkyl or un/substituted phenyl]-2-(3-oxo-3,4-dihydro-2H-benzo[b][1,4]thiazin-2-yl)acetamide were designed and synthesized. In vitro antifungal activity assay indicates that the 1,4-Benzothiazine has good antifungal activity against most of the tested pathogenic fungi i. e. Candida albicans, Trichophyton rubrum, Epidermophyton floccosum and Malassazia furfur. Some few compounds such as BTA-43 and BTA-56 have significant antifungal activity and broader spectrum, which are promising leads for the development of novel antifungal agents. The structures of the synthesized compounds were established on the basis of IR, NMR, 13CNMR and Mass spectra data.