8a-methyl-2,8-dioxo-2,5,6,7,8,8a,9,9a-octahydronaphhto<2.3-b>furan

(1SR,3RS,6RS,7RS)-3-acetoxy-4-benzylidine-7-((tert-butyldimethylsilyl)oxy)-1,6-dimethylbicyclo<4.4.0>decan-4-one