(3a'S,4S,5'R,8'S,9'S,9a'S,10'R)-10'-allyl-2,2,2',2'-tetramethyl-7'-oxotetrahydro-5'H,7'H-spiro[[1,3]dioxolane-4,4'-[5,9]methano[1,3]dioxolo[4,5-d]oxocin]-8'-yl pivalate

(6R,7S,7aS)-7-((tert-butyldimethylsilyl)oxy)-2',2'-dimethyl-2,4-dioxo-4,5,7,7a-tetrahydro-2H-spiro[benzofuran-6,4'-[1,3]dioxolan]-3-yl pivalate

2,2-Dimethyl-propionic acid (S)-5-[(S)-(tert-butyl-dimethyl-silanyloxy)-((R)-2,2-dimethyl-[1,3]dioxolan-4-yl)-methyl]-4-(2-diazo-acetyl)-2-oxo-2,5-dihydro-furan-3-yl ester

(4S,6R,7S,7aS)-7-((tert-butyldimethylsilyl)oxy)-4-hydroxy-2',2'-dimethyl-2-oxo-4,5,7,7a-tetrahydro-2H-spiro[benzofuran-6,4'-[1,3]dioxolan]-3-yl pivalate

(S)-1-((3aS,4S,5R,6R,7S,7aS)-6-allyl-5-hydroxy-2,2,2',2'-tetramethyltetrahydro-5H-spiro[benzo[d][1,3]dioxole-4,4'-[1,3]dioxolan]-7-yl)-2-(dimethylamino)-2-oxoethyl pivalate