(1aS,7S,7aR,8S)-1a,1b,5,6,6a,7a-Hexahydro-1bα,6β-dihydroxy-6aα-methyl-8-(1-methyl-1-hydroxyethyl)spiro[2α,5α-methano-7H-oxireno[3,4]cyclopent[1,2-d]oxepine-7,2'-oxiran]-3(2H)-one