To a solution of 1-{10-[(4-bromophenyl)sulfonyl]-10,11-dihydro-5H-pyrrolo[2,1-c][1,4]benzodiazepin-3-yl}-2,2,2-trichloroethanone of Step B (1.80 g, 3.297 mmol) and dimethyl sulfoxide (1.17 mL, 16.487 mmol) in dry acetonitrile (30 mL) at room temperature under nitrogen was added 3-(aminomethyl)pyridine (0.67 mL, 6.595 mmol) and the reaction mixture heated to reflux for 20 hours. The cooled reaction mixture was concentrated in vacuo, the oily residue dissolved in ethyl acetate (100 mL), washed with 1M sodium hydroxide (2×100 mL), water (100 mL) and brine (100 mL), dried over anhydrous magnesium sulfate, filtered and concentrated in vacuo to give a yellow foam. Purification by flash chromatography using a solvent gradient of 0 to 3% methanol in dichloromethane gave the title compound (1.61 g, 91%) as a yellow foam.
