Synthesis and biological evaluation of benzo[7,8]chromeno[5,6-b][1,4]oxazin-3-ones

The O-methylmonoximes 2,3 of stenocarpoquinone-A and beta-lapachone reacted with methyl phenylacetate to give 1,4-benzoxazine derivatives 8a, 8b and oxazole 11a. Compound 8a was transformed to compounds 131, 13,1, 14. Treatment of compound 14 with osmium tetroxide afforded compounds 15, 16 and esterification of the latter gave the bis- and mono- esters 17(I), 17(II), 18. All products are strongly fluorescent. Compounds 8a,b, 11a, 13-18 (azabenzo analogues of khellactones) were tested for their ability to interact with DPPH, to compete with dimethylsulfoxide for hydroxyl radicals, to inhibit soybean lipoxygenase and trypsin activities in vitro. Compounds 16 and 171, were found to compete significantly with dimethylsulfoxide for hydroxyl radicals, whereas compounds 8a, 11a, 14 and 17, were found to inhibit strongly soybean lipoxygenase.