Spiro[5,1b,4-(epoxyethanylylidene)-1bH-oxireno[4,5]cyclopent[1,2-b]oxepin-7(3H),2'-oxiran]-9-one,hexahydro-3,3,6a-trimethyl-, (1aS,1bR,2'R,4S,5S,6aR,7aR)- (9CI)