A solution of 3-cyclopentyl-2-(3-nitro-phenyl)-propionic acid (432 mg, 1.64 mmol) in methylene chloride (16 mL) was cooled to 0° C. and then treated with a 2.0M solution of oxalyl chloride in methylene chloride (0.90 mL, 1.80 mmol) and a few drops of N,N-dimethylformamide. The reaction mixture was stirred at 0° C. for 15 min and at 25° C. for 1.2 h. The reaction mixture was then treated with a solution of 2-aminothiazole (361.4 mg, 3.61 mmol) and N,N-diisopropylethylamine (0.70 mL, 3.93 mmol) in tetrahydrofuran (16 mL). The reaction mixture was stirred at 25° C. for 6 h. At this time, the reaction was concentrated in vacuo. Flash chromatography (Merck Silica gel 60, 230-400 mesh 70/30 hexanes/ethyl acetate) afforded 3-cyclopentyl-2-(nitrophenyl)-N-thiazol-2-yl-propionamide (409.3 mg, 72.2%) as a tan solid; mp 171-174° C.; EI-HRMS m/e calcd for C17H19N3O3S (M+) 345.1147, found 345.1153.
