To a solution containing 2(R)-(3-chloro-4-methanesulfonyl-phenyl)-3-cyclopentyl-propionic acid (prepared as in PCT WO 2004/052869 A1, Example 1, 2.66 g, 8.04 mmol) in methylene chloride (20 mL), a 2.0 M solution of oxalylchloride in methylene chloride (4.42 mL, 8.84 mmol) was added and allowed to stir for 1 h at 0° C. then for 1 h at 25° C. 2,6-lutidine (1.12 g, 10.0 mmol) was then added dropwise at 0° C., turning the solution light brown and resulting in effervescence. To this solution was added (3-amino-pyrazol-1-yl)-propionic acid tert-butyl ester (1.87 g, 8.84 mmol) dissolved in methylene chloride (5 mL). The reaction was allowed to proceed at 0° C. for 1 h and then overnight at 25° C. The reaction was washed with 1.0 M aqueous hydrochloric acid solution (20 mL) and the organic layer was dried with anhydrous sodium sulfate. The solvent was then removed in vacuo and was purified by ISCO flash column chromatography (Teledyne Isco RediSep Flash Column 120 g; 10% ethyl acetate/methylene chloride) to afford 3-{3-[2(R)-(3-chloro-4-methanesulfonyl-phenyl)-3-cyclopentyl-propionylamino]-pyrazol-1-yl}-propionic acid tert-butyl ester (3.06 g, 73%) as a white solid: ESI-LRMS m/e calcd for C25H34ClN3O5S [M+] 523.2, found 524.4 [M+H+]; 1H NMR (400 MHz, CDCl3) δ ppm 1.03-1.20 (m, 2H, CH2), 1.40 (s, 9H, 3×CH3), 1.39-1.92 (m, 8H, 4×CH2), 2.10-2.31 (m, 1H, CH), 2.70 (t, J=6.6 Hz, 2H, COCH2), 3.25 (s, 3H, SO2CH3), 3.57 (t, J=7.6 Hz, 1H, CH), 4.21 (t, J=6.6 Hz, 2H, NCH2), 6.60 (d, J=2.3 Hz, 1H, Ar), 7.28 (d, J=2.3 Hz, 1H, Ar), 7.45 (dd, Jo=8.2, Jm=1.7 Hz. 1H, Ar), 7.58 (d, Jm=1.7 Hz, 1H, Ar), 8.06 (d, Jo=8.2 Hz, 1H, Ar), 8.17 (s, 1H, NH).
