A solution of 3-(3-hydroxy-cyclopentyl)-2-(4-methanesulfonyl-phenyl)-N-thiazol-2-yl-propionamide (prepared as in Example 37, 155 mg, 0.393 mmol) in methylene chloride (3 mL) was treated with pyridinium chlorochromate (20 wt. % on basic alumina, 508 mg, 0.471 mmol). The resulting reaction mixture was stirred at 25° C. for 3 h, at which time, thin layer chromatography indicated a small amount of the 3-(3-hydroxy-cyclopentyl)-2-(4-methanesulfonyl-phenyl)-N-thiazol-2-yl-propionamide. The reaction mixture was then treated with an additional amount of pyridinium chlorochromate (20 wt. % on basic alumina, 127 mg, 0.118 mmol). The reaction mixture was allowed to stir at 25° C. for 1 h and then filtered through a pad of celite. The pad of celite was washed well with ethyl acetate until the washings indicated the absence of product by thin layer chromatography. The filtrate was then concentrated in vacuo. Flash chromatography (Merck Silica gel 60, 230–400 mesh, 1/3 hexanes/ethyl acetate to 100% ethyl acetate) afforded 2-(4-methanesulfonyl-phenyl)-3-(3-oxo-cyclopentyl)-N-thiazol-2-yl-propionamide (46 mg, 30%) as a white foam: mp 94–97° C.; FAB-HRMS m/e calcd for C18H20N2O4S2 (M+H)+ 393.0943, found 393.0948.
