(3R,3aS,6S,9aS,9bS)-2,3,3a,9,9a,9b-Hexahydro-3-hydroxy-3-(hydroxymethyl)-6-(3-chloro-2-buten-1-yl)-3a,6-dimethyl-1H-benz(e)indene-5,7-(4H,8H)-dione 3,1'-O-Isopropylidene Acetal