Spiro[2H-furo[2,3-e]isoindole-2,1′(2′H)-naphthalene]-7(3H)-hexanoic acid, α-[(1′R,2′R,4′aS,6′R,8′aS)-3′,4′,4′a,5′,6,6′,7′,8,8′,8′a-decahydro-4,6′-dihydroxy-2′,5′,5′,8′a-tetramethyl-6-oxospiro[2H-furo[2,3-e]isoindole-2,1′(2′H)-naphthalen]-7(3H)-yl]-3′,4′,4′a,5′,6,6′,7′,8,8′,8′a-decahydro-4,6′,7′-trihydroxy-2′,5′,5′,8′a-tetramethyl-6-oxo-, (αS,1′R,2′R,4′aS,6′S,7′R,8′aS)-