8H-2,7a-methano-10H-furo[3,4-c]pyrano[3,2-b]pyran-3,8(2H)-dione, tetrahydro-4-[(4-hydroxy-3-methoxyphenyl)methylene]-, (2R,4E,4aS,7aS,10aR)- InChI=1/C19H18O7/c1-23-13-7-10(2-3-12(13)20)6-11-15(21)14-8-18-4-5-24-16(11)19(18,26-14)9-25-17(18)22/h2-3,6-7,14,16,20H,4-5,8-9H2,1H3/b11-6-/t14-,16+,18?,19-/m1/s Polygalolide A rel-(2R,4E,4aS,7aS,10aR)-4-(4-hydroxy-3-methoxybenzylidene)tetrahydro-2,7a-methanofuro[3,4-c]pyrano[3,2-b]pyran-3,8-dione