A solution of 5-bromo-3-[4-(2-hydroxy-ethyl)-phenylamino]-1-methyl-1H-pyrazin-2-one (2) (1.2 g; 2.35 mmol) in CH2Cl2 (30 mL) was cooled to 0° C. and 1.5 mL of diisopropylethyl amine was added. A second solution containing 0.75 mL mesyl chloride in 3 mL CH2Cl2 was added dropwise to the stirring reaction solution under N2 and the reaction allowed to warm to rt for 1 hr. 0.1N Sodium hydroxide was then added carefully to the reaction, and the layers separated. The CH2Cl2 layer was washed with brine and dried over solid sodium sulfate, then filtered and evaporated to a light red-brown oil (1.5 g). The crude methanesulfonic acid 2-(4-{6-[3-(4-tert-butyl-benzoylamino)-2-methyl-phenyl]-4-methyl-3-oxo-3,4-dihydro-pyrazin-2-ylamino}-phenyl)-ethyl ester (3) was used directly in subsequent reactions.
