O.[OH:2][CH2:3][C@H:4]1[CH2:8][CH2:7][CH2:6][N:5]1[C:9]([O:11][C:12]([CH3:15])([CH3:14])[CH3:13])=[O:10]>C(Cl)Cl.[Cr](Cl)([O-])(=O)=O.[NH+]1C=CC=CC=1>[CH:3]([C@H:4]1[CH2:8][CH2:7][CH2:6][N:5]1[C:9]([O:11][C:12]([CH3:15])([CH3:14])[CH3:13])=[O:10])=[O:2]To a water cooled (25° C.) solution of 10.0 g of (R)-2-(hydroxymethyl)-1-pyrrolidinecarboxylic acid, 1,1-dimethylethyl ester in 250 ml of dry methylene chloride is added in one portion 16.0 g of pyridinium chlorochromate, 36.0 g of dried, crushed 4Å molecular sieves and 4.5 ml of glacial acetic acid. The resulting mixture is stirred at 25° C. for one hour. Twenty-five grams of diatomaceous earth and 500 ml of diethyl ether is added, the suspension is filtered through a pad of diatomaceous earth and the filtrate concentrated in vacuo. The residue is dissolved in diethyl ether and is passed through a short column of silica gel using diethyl ether as the eluant. The first two 500 ml fractions contain the desired aldehyde. The solvent is concentrated in vacuo to give 10.1 g of desired product.
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