Butyric acid (1aR)-1aα,2β,5,5a,6,9,10,10aα-octahydro-5β,5aβ-dihydroxy-4-hydroxymethyl-1,1,7,9α-tetramethyl-11-oxo-1H-2α,8aα-methanocyclopenta[a]cyclopropa[e]cyclodecen-6β-yl ester