Pyridine → {3-[2(R)-(3-chloro-4-methanesulfonyl-phenyl)-3-cyclopentyl-propionylamino]-pyrazol-1-yl}-acetic acid tert-butyl ester

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Triphenylphosphine (1.66 g, 6.33 mmol) was dissolved in methylene chloride (40 mL) and cooled to 0° C. To this solution was added N-bromosuccinimide (1.27 g, 7.17 mmol) and was stirred at 0° C. until it was completely dissolved and became light purple in color. The 2(R)-(3-chloro-4-methanesulfonyl-phenyl)-3-cyclopentyl-propionic acid (prepared as in PCT WO 2004/052869 A1, Example 1, 1.40 g, 4.22 mmol) was then added and it was stirred at 0° C. for 20 min and then warmed to 25° C. and stirred for 30 min. After such time, (3-amino-pyrazol-1-yl)-acetic acid tert-butyl ester (833 mg, 4.22 mmol) and pyridine (1.03 mL, 6.33 mmol) were added and it was stirred at 25° C. for 16 h. The reaction was then diluted with water (30 mL) and then extracted with methylene chloride (3×15 mL). The organic layers were then combined and dried over magnesium sulfate, filtered and concentrated in vacuo. Flash column chromatography (Merck silica gel 60, 40-63 μm; 50% ethyl acetate/hexanes) followed by reverse phase preparative HPLC purification (Column: Thomson C18 ODSA, 5 micron, 50×21.2 mm ID; 30% acetonitrile/water to 100% acetonitrile/water; 30 mL/min flow rate for 15 min run) afforded {3-[2(R)-(3-chloro-4-methanesulfonyl-phenyl)-3-cyclopentyl-propionylamino]-pyrazol-1-yl}-acetic acid tert-butyl ester (1.20 g, 56%) as a white solid: ESI-LRMS m/e calcd for C24H32ClN3O5S [M+] 509.2, found 510.1 [M+H+].

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