(r)-5-Biphenyl-4-ylmethyl-3-[1-diisopropylamino-meth-(e)-ylidene]-2-oxo-pyrrolidine-1-carboxylic acid tert-butyl ester → (3R,5S)-5-biphenyl-4-ylmethyl-3-methyl-2-oxo-pyrrolidine-1-carboxylic acid tert-butyl ester

Participants

Reaction Steps

1.3 g (R)-5-Biphenyl-4-ylmethyl-3-[1-dimethylaminometh-(E/Z)-ylidene]-2-oxo-pyrrolidine-1-carboxylic acid tert-butyl ester (7-a, R1=Boc, R6=Me, R7=Me) is added to ethyl acetate (40 ml) at ambient temperature. 0.3 g of 10% Palladium on Carbon (Engelhard 4505) and one drop of aqueous sodium hydroxide solution are added to the mixture. The mixture is then pressurised under a hydrogen atmosphere to 4 bar. The mixture is stirred at ambient temperature and 4 bar hydrogen pressure for 4 days. The mixture is then filtered to remove the catalyst and concentrated under reduced pressure. The residue is then purified by column chromatography (ethyl acetate/hexane, 70:30) to afford (3R,5S)-5-biphenyl-4-ylmethyl-3-methyl-2-oxo-pyrrolidine-1-carboxylic acid tert-butyl ester (3-a, R1=Boc) and (3S,5S)-5-biphenyl-4-ylmethyl-3-methyl-2-oxo-pyrrolidine-1-carboxylic acid tert-butyl ester (3-b, R1=Boc). Diastereomer ratio 76:24 (3-a, R1=Boc:3-b, R1=Boc) as determined by hplc.

Provenance & Evidence