Triphenylphosphine → 2-(3-bromo-4-methanesulfonyl-phenyl)-3-cyclopentyl-N-pyrazin-2-yl-propionamide

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A solution of 2-(3-bromo-4-methanesulfonyl-phenyl)-3-cyclopentyl-propionic acid (prepared as in Example 148A, 375 mg, 1.0 mmol) and triphenylphosphine (446 mg, 1.7 mmol) in methylene chloride (5 mL) was cooled to 0° C. and then treated with N-bromosuccinimide (303 mg, 1.7 mmol) in small portions. The reaction mixture color changed from light yellow to a darker yellow then to brown. After the complete addition of the N-bromosuccinimide, the reaction mixture was allowed to warm to 25° C. over 30 min. The brown reaction mixture was then treated with 2-aminopyrazine (238 mg, 2.5 mmol). The resulting reaction mixture was stirred at 25° C. for 19 h. The reaction mixture was then concentrated in vacuo to remove methylene chloride. Biotage chromatography (FLASH 40S, Silica, 2/3 hexanes/ethyl acetate) afforded 2-(3-bromo-4-methanesulfonyl-phenyl)-3-cyclopentyl-N-pyrazin-2-yl-propionamide (72 mg, 16%) as pink foam: EI-HRMS m/e calcd for C19H22BrN3O3S (M+) 451.0565, found 451.0547.

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