(3a′S,4′R,5′S,5a′S,8a′R,8b′R)-5′-{[Dimethyl(2-methyl-2-propanyl)silyl]oxy}-7′-oxohexahydrospiro[cyclohexane-1,2′-[1,3]dioxolo[4,5-e][1,3]benzodioxol]-4′-yl (1S,4R)-4,7,7-trimethyl-3-oxo-2-oxabicyclo[2 .2.1]heptane-1-carboxylate

(3a′S,4′R,5′S,5a′S,8a′R,8b′R)-5′-{[Dimethyl(2-methyl-2-propanyl)silyl]oxy}-7′-oxohexahydrospiro[cyclohexane-1,2′-[1,3]dioxolo[4,5-e][1,3]benzodioxol]-4′-yl (1S,4R)-4,7,7-trimethyl-3-oxo-2-oxabicyclo[2 .2.1]heptane-1-carboxylate

2-Oxabicyclo[2.2.1]heptane-1-carboxylic acid, 4,7,7-trimethyl-3-oxo-, (3a′S,4′R,5′S,5a′S,8a′R,8b′R)-5′-[[(1,1-dimethylethyl)dimethylsilyl]oxy]hexahydro-7′-oxospiro[cyclohexane-1,2′-[1,3]dioxolo[4,5-e] [1,3]benzodioxol]-4′-yl ester, (1S,4R)-