Methyl bromoacetate → 6-Chloro-4'-(3-chlorophenyl)-2,3-dihydro-1'-[(methoxycarbonyl)-methyl]-2'-(2-methylphenyl)-2,6'-dioxo spiro[indole-3,3'-piperidine]-1-carboxylic acid tert-butyl ester

In a manner similar to the method described in example 24c, racemic (2′R,3R,4′S)-6-chloro-4′-(3-chlorophenyl)-2,3-dihydro-2′-(2-methylphenyl)-2,6′-dioxospiro[indole-3,3′-piperidine]-1-carboxylic acid tert-butyl ester (1.02 g, 1.86 mmol) prepared in example 24b was reacted with LiH (86 mg, 10.9 mmol) (Aldrich) and methyl bromoacetate (0.57 g, 3.72 mmol) (Aldrich) to give racemic 2′R,3R,4′S)-6-chloro-4′-(3-chlorophenyl)-2,3-dihydro-1′-[(methoxycarbonyl)-methyl]-2′-(2-methylphenyl)-2,6′-dioxospiro[indole-3,3′-piperidine]-1-carboxylic acid tert-butyl ester as a white solid (Yield: 0.37 g, 32%).