11,16,18,19-tetraoxapentacyclo[12.2.2.1~6,9~.0~1,15~.0~10,12~]nonadeca-6,8-diene-7-carboxaldehyde, 12-methyl-4-(1-methylethenyl)-17-oxo-, (1S,4R,10S,12R,14S,15S)-