N1C=CC=CC=1.[C:7]([O:15][C@@H:16]1[CH2:24][C@@H:19]2[O:20][C:21](=[O:23])[CH2:22][C@@H:18]2[C@H:17]1[CH2:25][OH:26])(=[O:14])[C:8]1[CH:13]=[CH:12][CH:11]=[CH:10][CH:9]=1>C(Cl)Cl.C1(C)C=CC=CC=1.[O-2].[O-2].[O-2].[Cr+6]>[C:7]([O:15][C@@H:16]1[CH2:24][C@@H:19]2[O:20][C:21](=[O:23])[CH2:22][C@@H:18]2[C@H:17]1[CH:25]=[O:26])(=[O:14])[C:8]1[CH:9]=[CH:10][CH:11]=[CH:12][CH:13]=1A suspension of anhydrous chromium trioxide (20.8 g, 208 mmol) in methylene chloride (400 mL) was stirred and cooled in an ice bath as anhydrous pyridine (32.7 mL, 406 mmol) was added. After 15 min at 0° C., the mixture was allowed to warm to ambient temperature for 2 h. The reaction mixture was cooled to 0° C. and treated with a pre-cooled solution of (3aR,4S,5R,6aS)-5-(benzoyloxy)hexahydro-4-(hydroxymethyl)-2H-cyclopenta[b]furan-2-one (Corey lactone, 9.4 g, 34 mmol) in methylene chloride (400 mL) After 5 min, the reaction was diluted with toluene (240 mL) and filtered. The solid was washed with toluene. The combined filtrate was concentrated to give (3aR,4R,5R,6aS)-5-(benzoyloxy)hexahydro-2-oxo-2H-cyclopenta[b]furan-4-carboxaldehyde. Toluene was added to give about 300 mL of solution.
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