Triethylamine → N-(5-bromo-thiazol-2-yl)-3-cyclopentyl-2-(4-methanesulfonyl-phenyl)-propionamide

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A solution of 3-cyclopentyl-2-(4-methanesulfonyl-phenyl)-propionic acid (prepared in Example 130, 300 mg, 1.01 mmol) and dry N,N-dimethylformamide (2 drops) in methylene chloride (3 mL) was cooled to 0° C. and then treated dropwise with oxalyl chloride (115 μL, 1.32 mmol). The reaction mixture was stirred at 0° C. for 10 min and then stirred at 25° C. for 1 h. The reaction mixture was concentrated in vacuo. The resulting yellow oil was dissolved in a small amount of methylene chloride and then slowly added to a solution of 2-amino-5-bromothiazole monohydrobromide (395 mg, 1.52 mmol) and triethylamine (424 μL, 3.04 mmol) in N,N-dimethylformamide (3 mL). The resulting reaction mixture was then stirred at 25° C. for 15 h. The resulting reaction mixture was partitioned between water (50 mL) and ethyl acetate (50 mL), and the layers were separated. The aqueous layer was further extracted with ethyl acetate (50 mL). The combined organic layers were then dried over magnesium sulfate, filtered, and concentrated in vacuo. Flash chromatography (Merck Silica gel 60, 230–400 mesh, 1/1 hexanes/ethyl acetate) afforded the N-(5-bromo-thiazol-2-yl)-3-cyclopentyl-2-(4-methanesulfonyl-phenyl)-propionamide (160 mg, 35%) as a tan foam: mp 73–75° C. (foam to gel); EI-HRMS m/e calcd for C18H21BrN2O3S2 (M+) 456.0177, found 456.0176.

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