2,6-Lutidine → N-{1-[2-(tert-butyl-dimethyl-silanyloxy)-ethyl]-1H-pyrazol-3-yl}-3-cyclopentyl-2-(R)-(4-methanesulfonyl-phenyl)-propionamide

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The 3-cyclopentyl-2-(R)-(4-methanesulfonyl-phenyl)-propionic acid (prepared as in PCT WO 2004/052869 A1, Example 3, 184 mg, 0.62 mmol) was dissolved in methylene chloride (3 mL) and a 2.0 M solution of oxalyl chloride in methylene chloride (31 μL, 0.62 mmol) was added and the reaction stirred at 25° C. for 10 min. The solution was chilled to 0° C. and 2,6-lutidine (144 μL, 1.24 mmol) was added dropwise. A strong exotherm and bubbling were observed. The solution continued to stir at 0° C. for 10 min. The 1-[2-(tert-butyl-dimethyl-silanyloxy)-ethyl]-1H-pyrazol-3-ylamine (prepared in Example 67, 150 mg, 0.62 mmol) was added as a solution in methylene chloride (3 mL), the ice bath was removed and the solution continued to stir at 25° C. for 25 min. The solution was diluted with methylene chloride (100 mL), washed with water (2×30 mL), saturated aqueous brine solution (1×20 mL), dried over magnesium sulfate and concentrated in vacuo to a beige foam. Purification by flash column chromatography (Merck silica gel 60, 40-63 μm; 40% ethyl acetate/hexanes) afforded N-{1-[2-(tert-butyl-dimethyl-silanyloxy)-ethyl]-1H-pyrazol-3-yl}-3-cyclopentyl-2-(R)-(4-methanesulfonyl-phenyl)-propionamide (150 mg, 44%) as a white foam: ESI-LRMS m/e calcd for C26H41N3O4SSi [M+] 519.26, found 520.36 [M+H+].

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