Synthesis of Novel Benzoxazole Derivatives: Exploration of Their Possible Pharmacological Profiles with Computational Studies

Based on the interaction with PDB protein 1PXX of the cox-2 enzyme, a novel series of substituted thiazolidinones (TZD 5a-s) and azetidinones (AZT 6a-s) was designed and synthesized. Molecules were synthesized from 2-mercapto benzoxazole (1) using both conventional and microwave irradiation methods, and their in-vitro antioxidant activity was evaluated using the DPPH free radical scavenging activity, as well as their in-vivo anti-inflammatory activity using the carrageenin-induced rat paw edema method. The reaction time, yield, and purity of microwave and conventionally produced molecules are compared in this work. The molecule ethyl 2-(benzoxazol-2-ylthio)acetate (2) is obtained by reacting 2-mercapto benzoxazole (1) with ethyl 2-chloroacetate in the presence of potassium carbonate and dry acetone. The molecule 2-(benzoxazol-2-ylthio)acetohydrazide (3) was synthesized by reacting ethyl 2-(benzoxazol-2-ylthio)acetate (2) with hydrazine hydrate in the presence of absolute alcohol. Compound 2-(benzoxazol-2-ylthio)acetohydrazide (3) on reacting with different aromatic and heterocyclic aldehyde derivative forms 2-(benzoxazol-2-ylthio)-N'-substituted acetohydrazide Schiff bases (4a-s). 2-(benzoxazol-2-ylthio)-N-(4-oxo-2-substituted thiazolidin-3-yl)acetamide (5a-s) i.e. thiazolidinones benzoxazole derivatives obtained on reacting Schiff bases (4a-s) with thioglycolic acid in a dioxane medium and anhydrous zinc chloride. The Schiff bases (4a-s) were converted into 2-(Benzo[d]oxazol-2-ylthio)-N-(3-chloro-2-oxo-4-substituted azetidin-1-yl)acetamide (6a-s) after treatment with chloroacetyl chloride in the presence of triethanol amine and dioxane. This study focuses on screening of novel synthesized benzoxazole derivatives for in vitro antioxidant, in vivo anti-inflammatory activity, and the evaluation of ulcerogenic activity. The in vivo activity is correlated with the in silico activity, the 3 D QSAR studies were performed for all the compounds by using computer program i.e. SYBYL-X 2.1.1 software. The best CoMFA and CoMSIA models were obtained for the training set compounds with 0.753 and 0.646 leave-one-out coefficients (q2), 0.714 and 0.619 cross validated correlation coefficients (r2cv), and 0.975 and 0.983 conventional coefficients (r2), respectively. Both models were validated with a test set of eight compounds, giving the CoMFA and CoMSIA models a satisfactory prediction (r2pred) of 0.788 and 0.663, respectively. The findings of the study would provide valuable information for the design of new compounds and would also help in predicting the activity of designed compounds. To identify the lead molecule docking studies are performed on COX-2 enzyme of protein 1PXX, the molecules 5c, 5q, 5j, 6q, and 6 g derivatives obtained good - c-docker interaction energy respectively, and in vivo acute ulcerogenic activity.