((3R,3aS,4S,6aS)-4-((2R,3R)-3-(ethanoyloxy)-4-hydroxy-2-methylbutyl)-3a-hydroxy-1,3-dimethyl-2,6-dioxohexahydro-1H-furo[3,4-b]pyrrol-6a-yl)methyl ethanoate

(3S,6S,7aR,E)-methyl 7-((3R,4R)-5-(benzyloxy)-4-(tert-butyldimethylsilyloxy)-3-methylpentylidene)-3-tert-butyl-6-methyl-5-oxohexahydropyrrolo[1,2-c]oxazole-7a-carboxylate

(3S,7aR)-methyl 7-((3R,4R)-5-(benzyloxy)-4-(tert-butyldimethylsilyloxy)-3-methylpentyl)-3-tert-butyl-6-methyl-5-oxo-1,3,5,7a-tetrahydropyrrolo[1,2-c]oxazole-7a-carboxylate

(3R,3aS,4S,6aS)-4-[(2R,3R)-4-(benzyloxy)-3-hydroxy-2-methylbutyl]-3a-hydroxy-6a-(hydroxymethyl)-3-methyldihydro-1H-furo[3,4-b]pyrrole-2,6(3H,4H)-dione

(3S,7aS)-methyl 3-tert-butyl-6-methyl-5-oxo-7-(trifluoromethylsulfonyloxy)-1,3,5,7a-tetrahydropyrrolo[1,2-c]oxazole-7a-carboxylate

(3S,7aR)-methyl 7-((3R,4R)-5-(benzyloxy)-4-hydroxy-3-methylpentyl)-3-tert-butyl-6-methyl-5-oxo-1,3,5,7a-tetrahydropyrrolo[1,2-c]oxazole-7a-carboxylate

(3S,6R,6aS,7S,9aS)-7-[(2R,3R)-4-(benzyloxy)-3-{[tert-butyl(dimethyl)silyl]oxy}-2-methylbutyl]-3-tert-butyl-6a-hydroxy-6-methyldihydrofuro[3',4':2,3]pyrrolo[1,2-c][1,3]oxazole-5,9(6H)-dione

((3R,3aS,4S,6aS)-4-((2R,3R)-4-(benzyloxy)-3-(ethanoyloxy)-2-methylbutyl)-3a-hydroxy-1,3-dimethyl-2,6-dioxohexahydro-1H-furo[3,4-b]pyrrol-6a-yl)methyl ethanoate

(3S,7aR)-methyl 7-((3R,4R,1E)-5-(benzyloxy)-4-hydroxy-3-methylpent-1-enyl)-3-tert-butyl-6-methyl-5-oxo-1,3,5,7a-tetrahydropyrrolo[1,2-c]oxazole-7a-carboxylate

(3S,6S,6aS,7S,9aS)-7-[(2R,3R)-4-(benzyloxy)-3-{[tert-butyl(dimethyl)silyl]oxy}-2-methylbutyl]-3-tert-butyl-6a-hydroxy-6-methyldihydrofuro[3',4':2,3]pyrrolo[1,2-c][1,3]oxazole-5,9(6H)-dione

(3R,3aS,4S,6aS)-4-{(2R,3R)-4-(benzyloxy)-2-methyl-3-[triethylsilyloxy]butyl}-3a-hydroxy-3-methyl-6a{triethylsilyloxymethyl}dihydro-1H-furo[3,4-b]pyrrole-2,6(3H,4H)-dione

(2R,3R)-1-(menzyloxy)-3-methyl-5-(tri-n-butylstannyl)-4-penten-2-ol

methyl (3S,7aS)-3-(tert-butyl)-7-hydroxy-6-methyl-5-oxo-1H,3H-pyrrolo[1,2-c]oxazole-7a(5H)-carboxylate