Synthesis and Potential Applications of Oxo-Quinolines and their Analogues

Abstract

The present dissertation work deals with the successful synthesis of a diversity of quinolones and their analogues. The overall research work is broadly classified into three parts: (A) Synthesis of quinolones, (B) Synthesis of analogues of quinolones, and (C) Biological screening. For fulfilling the first goal, work on six different projects was carried out. In the first plan, compound 240 was prepared which was utilized for plan ‘2’ in synthesizing compounds 241-247 using various aldehydes. For third strategy, hydrazides 267-274 were prepared from corresponding quinolone hydrazide (266) and indenoquinoxalines (225-231). A series of compounds 257-264 were prepared effectively through rearrangement of hydrazino indenoquinoxalines (232-239) using diazotization methodology. In the 5th synthetic approach, N-methyl-1,2,3,4-tetrahydroquinoline-2,3,4-trione-3-oxime” (253) was reacted with various amino acids and the final products obtained were characterized which came out to be identical in all cases; compound 254. Coming toward the 6th synthetic strategy, reduction of 6-bromo-1,2,3,4-tetrahydroquinoline-2,3,4-trione-3-oxime (252) to 6-bromo During the course of research a number of essential starting compounds were prepared in the lab. All the synthesized compounds were characterized through spectroscopic analysis. After the successful synthesis of the desired products, biological screening of most of them was carried out. For the fulfillment of this criteria following biological activity protocols were employed: acetylcholinesterase (AChE) inhibition studies, α-glucosidase inhibition studies, urease inhibition studies, ABTS antioxidant studies and DPPH antioxidant studies. Enzyme inhibition assays were performed for the compounds 201, 208-239, 267 272, 274 and 281-288. In case of AChE enzyme inhibition studies, synthesized products 201, 212, 225, 231, 234 and 274 were found to be even more effective than the standard used. For α-glucosidase enzyme inhibition studies, compounds 218, 222, 283, 284, 286 and 287 were found to be more potent than the standard used. In case of urease inhibition studies, compound 229 was more active in inhibiting the enzyme than the standard used. Overall enzymatic activities performance for the synthesized product ranges from poor to remarkable. ABTS antioxidant studies were carried out for the compounds 232-239 and DPPH antioxidant studies were performed for 199, 200, 205, 206 and 240. In case of antioxidant activities, none of the compound showed good results.