Methyl (2R,2aS,5aR,5a1R,51'R,8a'R,9a'S,9a1'S,10'S,11'S,12bR,15a'R)-9a'-ethyl-51',10',11'-trihydroxy-4,5,51',6,8,8a',9a',9a1',11',12',13,14,14',15'-tetradecahydro-1H,2aH,5a1H,6'H,8'H,9'H,10'H-spiro[furo[2',3':7,8]indolizino[8,1-cd]carbazole-2,7'-indolizino