Succinic anhydride → (R)-4-biphenyl-4-yl-3-(3-carboxy-propionylamino)-butyric acid ethyl ester

Participants

Reaction Steps

To (R)-ethyl-4-(biphenyl-4-yl)-3-(tert-butoxycarbonylamino)butanoate (230.1 mg, 0.600 mmol) is added a solution of HCl in 1,4-dioxane (3.00 mL, 12.00 mmol) at room temperature. After stirring for 1 hour, the reaction mixture is concentrated under reduced pressure to give (R)-3-amino-4-biphenyl-4-yl-butyric acid ethyl ester hydrochloride. A solution of (R)-3-amino-4-biphenyl-4-yl-butyric acid ethyl ester hydrochloride, succinic anhydride (72.1 mg, 0.720 mmol) and DIPEA (0.126 mL, 0.720 mmol) in dichloromethane (4 mL) is allowed to stir for 1 hour. The reaction is quenched with 10% aqueous citric acid and extracted with dichloromethane. The organic layer is separated and concentrated under reduced pressure. The obtained residue is purified by flash column chromatography on CN-modified silica gel (eluent: heptane/EtOAc=100:0 to 0:100) and by RP-HPLC (SunFire C18, H2O (0.1% TFA)/CH3CN) to give (R)-4-(1-(biphenyl-4-yl)-4-ethoxy-4-oxobutan-2-ylamino)-4-oxobutanoic acid (148.2 mg). HPLC retention time=1.64 minutes (condition A); MS (m+1)=384.1; 1H NMR (400 MHz, ACETONITRILE-d3) δ ppm 1.21 (t, J=7.07 Hz, 3 H) 2.31-2.39 (m, 2 H) 2.40-2.56 (m, 4 H) 2.77-2.92 (m, 2 H) 4.08 (q, J=7.24 Hz, 2 H) 4.33-4.48 (m, 1 H) 6.62 (d, J=8.34 Hz, 1 H) 7.30 (d, J=8.08 Hz, 2 H) 7.32-7.39 (m, 1 H) 7.41-7.49 (m, 2 H) 7.54-7.60 (m, 2H) 7.60-7.67 (m, 2 H) 10.02 (br. s., 1 H).

Provenance & Evidence