Methanesulfonyl chloride → 1-(2,4-Dimethoxypyrimidin-5-yl)-N,N-diethyl-1,2,3,4-tetrahydropyrimido[1,2-a]benzimidazol-6-amine

To a solution of 3-{7-(diethylamino)-2-[(2,4-dimethoxypyrimidin-5-yl)amino]-1H-benzimidazol-1-yl}propan-1-ol (Reference Example 97; 90 mg, 0.224 mmol) in pyridine (2.0 mL) was added methanesulfonyl chloride (0.035 mL, 0.449 mmol) at 0° C. The mixture was warmed to room temperature and stirred for 3 hr. Aqueous sodium bicarbonate was added and the mixture was extracted with ethyl acetate. Organic layer was washed with brine, dried over anhydrous sodium sulfate and concentrated in vacuo to give a solid, which was recrystallized from n-hexane/ethyl acetate to give the title compound (50 mg, 0.131 mmol, 58%) as a pale brown solid.