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

4-Methylchromene-2,7,8-trione 1 reacts with stabilized 2a-c and non-stabili zed ylides 11a-c bearing alpha -methylene group to give 7,8-fused 1,3-dioxo locoumarins 4a-c and 12a-c along with betaine 6 and 7-hydroxycoumarin deriv ative 9. The reaction of 4,5-fused 1,3-dioxolo-o-benzoquinone 13 with the y lide 14 leads to 4-ethoxycarbonylayapin 18 and benzofuranone 19. Deethoxyca rbonylation of 18 gives ayapin 20. Compounds 4b, 12a-c, 18 and 20 were test ed 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, beta -glucuronidas e and soybean lipoxygenase activity in vitro. These compounds were also tes ted 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 r educing ability was found to be low and no inhibition on soybean lipoxygena se was recorded.