To a mixture of (2R,4S)-4-amino-5-biphenyl-4-yl-2-methyl-pentanoic acid ethyl ester hydrochloride (70 mg, 0.201 mmol) and 3-chlorocarbonylbenzoic acid methyl ester (0.302 mmol) in methylene chloride (0.5 mL) is added pyridine (0.5 mL) and the mixture is stirred at room temperature for 24 hours. The solvents are removed under reduced pressure and ethyl acetate is added. The solution is washed with aqueous 1M HCl and brine and the organic phase is dried over sodium sulfate. The solvent is removed under reduced pressure and the residue is purified by column chromatography using methylene chloride to furnish N-((1S,3R)-1-biphenyl-4-ylmethyl-3-ethoxycarbonyl-butyl)-isophthalamic acid. Next, to a solution of N-((1S,3R)-1-biphenyl-4-ylmethyl-3-ethoxycarbonyl-butyl)-isophthalamic acid (0.287 mmol) in ethanol (10 mL) is added aqueous 1M NaOH (1.2 mL, 1.12 mmol) and the mixture is stirred at 50-60° C. for 5 hours. The ethanol is removed under reduced pressure and water is added. The solution is acidified with 1M HCl and the mixture is extracted with ethyl acetate. The organic phase is dried over sodium sulfate and the solvent is removed under reduced pressure. The residue is purified by preparative HPLC using a gradient of MeCN/water (0.1% TFA). The proper fractions are lyophilized to furnish N-((1S,3R)-1-biphenyl-4-ylmethyl-3-carboxy-butyl)-isophthalamic acid. HPLC Retention time 1.05 minutes (condition A); MS 432.3 (M+1); 1H NMR (400 MHz, DMSO-d6) δ ppm 1.09 (d, J=7.07 Hz, 3H), 1.60 (m, 1H), 1.89 (m, 1H), 2.47 (m, 1H), 2.86 (m, 2H), 4.27 (m, 1H), 7.27-7.35 (m, 3H), 7.34 (t, 1H), 7.43 (t, 2H), 7.55-7.66 (m, 5H), 8.01-8.07 (m, 2H), 8.39 (s, 1H), 8.47 (d, J=8.46 Hz, 1H).
