(3aR,5R,6S,7S,7aR)-7-(tert-Butyl-diphenyl-silanyloxy)-2,2-diethyl-5,6-dihydroxy-hexahydro-benzo[1,3]dioxole-5-carboxylic acid methyl ester

(3aR,4aR,7aR,8R,8aS)-8-(tert-Butyl-diphenyl-silanyloxy)-6,6-diethyl-2,2-dimethyl-tetrahydro-benzo[1,2-d;4,5-d']bis[1,3]dioxole-3a-carboxylic acid methyl ester