Next, to a solution of 1H-pyrazole-3-carboxylic acid (20.5 mg, 0.183 mmol) in DMF (1 mL) is added diisopropylethylamine (0.032 mL, 0.183 mmol). After 15 min a solution of the above (2R,4S)-5-biphenyl-4-yl-4-isocyanato-2-methyl-pentanoic acid benzyl ester in DMF (1 mL) is added dropwise and the mixture is stirred at room temperature for 18 hours. The mixture is purified by preparative HPLC using a gradient of 10% MeCN to 100% MeCN (0.1% TFA). Lyophilization of the appropriate fractions furnishes 1-((1S,3R)-3-benzyloxycarbonyl-1-biphenyl-4-ylmethyl-butylcarbamoyl)-1H-pyrazole-3-carboxylic acid. Next, a solution of 1-((1S,3R)-3-benzyloxycarbonyl-1-biphenyl-4-ylmethyl-butylcarbamoyl)-1H-pyrazole-3-carboxylic acid (60 mg, 0.117 mmol) in EtOAc (10 mL) is hydrogenated over 10% Pd/C (40 mg) at 1 atm for 5 hours. The catalyst is filtered through Celite and the filtrate evaporated under reduced pressure. The residue is purified by preparative HPLC using a gradient of 10% MeCN to 100% MeCN (0.1% TFA). Lyophilization of the appropriate fractions furnishes 1-((1S,3R)-1-biphenyl-4-ylmethyl-3-carboxy-butylcarbamoyl)-1H-pyrazole-3-carboxylic acid. HPLC Retention time 0.96 minutes (condition A); MS 422.0 (M+1); 1H NMR (400 MHz, DMSO-d6) δ ppm 1.09 (d, J=7.07Hz, 3H), 1.78 (m, 1H), 1.88 (m, 1H), 2.45 (m, 1H), 2.86 (m, 1H), 2.98 (m, 1H), 4.14 (m, 1H), 6.84 (d, J=2.65Hz, 1H), 7.28 (d, J=8.34Hz, 2H), 7.33 (t, 1H), 7.43 (t, 2H), 7.56 (d, J=8.34Hz, 2H), 7.63 (d, J=7.07Hz, 2H), 8.29 (d, J=2.78Hz, 1H), 8.58 (d, J=9.09Hz, 1H).
