15,16-Epoxy-1,3,13(16),14-clerodatetraen-20,12-olide-18,19-dioic acid dimethylester Crotozambefuran A InChI=1/C22H24O7/c1-13-7-9-21(19(24)27-3)15(18(23)26-2)5-4-6-17(21)22(13)11-16(29-20(22)25)14-8-10-28-12-14/h4-6,8,10,12-13,16-17H,7,9,11H2,1-3H3/t13?,16?,17?,21?,22-/m1/s dimethyl 5-(3-furyl)-2'-methyl-2-oxo-3',4,4',5-tetrahydro-2'H-spiro[furan-3,1'-naphthalene]-4a',5'(8a'H)-dicarboxylate spiro[furan-3(2H),1'(2'H)-naphthalene]-4'a,5'(8a'H)-dicarboxylic acid, 5-(3-furanyl)-3',4,4',5-tetrahydro-2'-methyl-2-oxo-, dimethyl ester, (3R)-