2-Butenoic acid, 2-methyl-, 7,8-dihydro-8,8-dimethyl-2-oxo-2H,6H-benzo(1,2-b:5,4-b')dipyran-6,7-diyl ester, (6R-(6alpha(Z),7alpha(Z)))- 21800-48-6 Xanthalin