Reactions of 4-methylchromene-2,7,8-trione with phosphonium ylides. Synthesis and evaluation of fused 1,3-dioxolocoumarins as antioxidants and antiinflammatories

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Abstract
4-Methylchromene-2,7,8-trione 1 reacts with stabilized 2a–c and non-stabilized ylides 11a–c bearing an α-methylene group to give 7,8-fused 1,3-dioxolocoumarins 4a–c and 12a–c along with betaine 6 and 7-hydroxycoumarin derivative 9. The reaction of 4,5-fused 1,3-dioxolo-o-benzoquinone 13 with the ylide 14 leads to 4-ethoxycarbonylayapin 18 and benzofuranone 19. Deethoxycarbonylation of 18 gives ayapin 20. Compounds 4b, 12a–c, 18 and 20 were tested for their ability to interact with 1,1-diphenyl-2-picrylhydrazyl stable free radical (DPPH), to scavenge superoxide anion radicals, to compete with DMSO for hydroxyl radicals, and to inhibit proteolysis, β-glucuronidase and soybean lipoxygenase activity in vitro. These compounds were also tested for their effect on the ferrous ion-stimulated peroxidation of linoleic acid. They showed a potent inhibitory effect (55–57%) against inflammation induced by carrageenan in the rat paw edema model. On the contrary their reducing ability was found to be low and no inhibition on soybean lipoxygenase was recorded.

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