A solution of 2(R)-(3-chloro-4-methanesulfonyl-phenyl)-3-(4-oxo-cyclohexyl)-propionic acid (prepared as in Example 60, 263 mg, 0.73 mmol) and triphenylphosphine (250 mg, 0.95 mmol) in methylene chloride (5.0 mL) cooled to 0° C. was treated with N-bromosuccinimide (167 mg, 0.95 mmol) in small portions. After the complete addition of N-bromosuccinimide, the reaction mixture was allowed to warm to 25° C. over 30 min. The bright orange reaction mixture was then treated with 2-amino-5-methylpyrazine (160 mg, 1.46 mmol) and 2,6-lutidine (0.36 mL, 2.92 mmol). The resulting reaction mixture was stirred at 25° C. for 4 h. The reaction mixture was then diluted with methylene chloride (25 mL) and was successively washed with a 10% aqueous hydrochloric acid solution 1×20 mL), a saturated aqueous sodium bicarbonate solution 1×20 mL) and water 1×20 mL), dried over sodium sulfate, filtered, and concentrated in vacuo. Biotage chromatography (FLASH 40S, Silica, 65/35 hexanes/ethyl acetate to 3/7 hexanes/ethyl acetate) afforded 2(R)-(3-chloro-4-methanesulfonyl-phenyl)-N-(5-methyl-pyrazin-2-yl)-3-(4-oxo-cyclohexyl)-propionamide (158 mg, 48%) as a white foam: [α]23589=−41.52° (c=0.33, chloroform); EI-HRMS m/e calcd for C20H21Cl2N3O4S (M+H)+ 450.1249. found 450.1253.
