Benzylamine → (2S,3S,5R)-2-benzyl-3-benzylamino-5-ethyl-pyrrolidine-1-carboxylic acid isopropyl ester

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Reaction Steps

To a solution of a diastereomeric mixture of (2S)-2-benzyl-5-ethyl-3-oxo-pyrrolidine-1-carboxylic acid isopropyl ester (0.29 mmol; 84 mg) and benzylamine (0.58 mmol; 62.1 mg) in MeOH (1.5 mL) is added titanium(IV) isopropoxide (0.58 mmol; 165 mg) at room temperature under nitrogen. After stirring for 5 hours, NaBH4 (0.58 mmol; 22 mg) is added to the mixture at 0° C. The mixture is stirred for 2 hours at room temperature and then diluted with water and aqueous 0.1 M NaOH solution. The solution is filtered and concentrated under reduced pressure. To the residue is added water and dichloromethane. The product is extracted twice with dichloromethane. The combined organic layer is washed with brine, dried over Na2SO4, filtered, and concentrated under reduced pressure. The residue is purified by column chromatography on silica gel (n-hexane/EtOAc) to give (2S,3S,5R)-2-benzyl-3-benzylamino-5-ethyl-pyrrolidine-1-carboxylic acid isopropyl ester (61 mg, 55%); ESI-MS m/z: 381 [M++1], Retention time 1.77 min (condition A).

Provenance & Evidence