Ethyl (2R,4S)-4-([1,1'-biphenyl]-4-ylmethyl)-2-methyl-4-(2,5-dioxopyrrolidin-1-yl)butanoate → Sacubitril Impurity 3

Participants

Reaction Conditions

Reaction Steps

To a mixture of (2S,4S)-4-amino-5-biphenyl-4-yl-2-methylpentanoic acid ethyl ester hydrochloride (3-b, R1=R2=H, R3=Et) [9:1 diastereoisomer mixture [(2S,4S):(2R,4S)]] (840 mg) in isopropyl acetate (10 ml) triethylamine (418 mg) is added. The mixture is then stirred at 55° C. for 1 h and then filtered. The filtrate is heated at reflux for 24 hours. To the mixture is added saturated ammonium chloride solution and the phases are separated. The organic layer is concentrated to dryness. The residue is purified by chromatography, eluting first with IPA/Heptane 2:1 then with a mixture 1:1 to afford (3S,5S)-5-biphenyl-4-ylmethyl-3-methylpyrrolidin-2-one (2-b, R1=H) and (3R,5S)-5-biphenyl-4-ylmethyl-3-methylpyrrolidin-2-one (2-a, R1=H). Ratio of diastereoisomers determined by 1H NMR to be 9:1 [(3S,5S):(3R,5S)]. 1H NMR (CDCl3) for (2-b, R1=H): 1.15 (3H), 1.38 (1H), 2.42 (2H), 2.63 (1H), 2.82 (1H), 3.75 (1H), 5.51 (1H), 7.17 (2H), 7.28 (1H), 7.37 (2H), 7.49 (4H). Spectroscopic data for (2-a, R1=H) as in Example 6.

Provenance & Evidence