(3a'S,4S,5'R,8'S,9'S,9a'S,10'R)-10'-(2-chloroethyl)-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 carbamate

(3a'S,4S,6'R,7a'S,10a'S,10b'R,11'R)-11'-(2-chloroethyl)-2,2,9',9'-tetramethyldihydro-6'H-spiro[[1,3]dioxolane-4,7'-[6,10b]methano[1,3]dioxolo[4',5':5,6]oxocino[4,3-d]oxazole]-2',4'(1'H,3a'H)-dione

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

(3a'S,4S,5'R,8'S,9'S,9a'S,10'R)-9'-amino-8'-hydroxy-2,2,2',2'-tetramethyl-10'-vinyltetrahydro-5'H,7'H-spiro[[1,3]dioxolane-4,4'-[5,9]methano[1,3]dioxolo[4,5-d]oxocin]-7'-one

(S)-2-(dimethylamino)-2-oxo-1-((3aS,4R,7S,7aS)-2,2,2',2'-tetramethyl-6-oxotetrahydro-5H-spiro[benzo[d][1,3]dioxole-4,4'-[1,3]dioxolan]-7-yl)ethyl pivalate

(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

(3a'S,4S,5'R,8'S,9'R,9a'S,10'R)-10'-allyl-8'-hydroxy-2,2,2',2'-tetramethyltetrahydro-5'H,7'H-spiro[[1,3]dioxolane-4,4'-[5,9]methano[1,3]dioxolo[4,5-d]oxocin]-7'-one

(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

(3a'S,4S,5'R,8'S,9'S,9a'S,10'R)-10'-(2-hydroxyethyl)-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 carbamate

(S)-2-(dimethylamino)-2-oxo-1-((3aS,4R,7S,7aS)-2,2,2',2'-tetramethyl-6-methylenetetrahydro-5H-spiro[benzo[d][1,3]dioxole-4,4'-[1,3]dioxolan]-7-yl)ethyl pivalate

N,N'-bis-Boc-S-methyl-isothiourea

(S)-2-(dimethylamino)-2-oxo-1-((3aS,4R,7S,7aS)-2,2,2',2'-tetramethyl-6-methylene-5-oxotetrahydro-5H-spiro[benzo[d][1,3]dioxole-4,4'-[1,3]dioxolan]-7-yl)ethyl 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