Pyridine-3-sulfonyl chloride hydrochloride (20 mg, 0.093 mmol) was dissolved in a mixture of dichloromethane and aqueous saturated NaHCO3 and the organic layer was dried (MgSO4) and evaporated to give pyridine-3-sulfonyl chloride. tert-Butyl 10-chloro-1,3,4,8-tetrahydro-2H-[1,4]oxazepino[6,7-e]indole-2-carboxylate (Intermediate 20, 10 mg, 0.031 mmol) was dissolved in DMF (1 mL) and sodium hydride (60% in mineral oil, 2.5 mg, 0.062 mmol) was added. The mixture was stirred for 10 minutes before pyridine-3-sulfonyl chloride (0.093 mmol) in DMF (1 mL) was added. The reaction mixture was stirred at room temperature for 10 minutes before TFA (2 mL) was added and the mixture was heated at 50° C. overnight. The reaction mixture was evaporated and the crude material was purified by preparative HPLC (ACE C8, 0.1% TFA-CH3CN) to give the title compound as a white solid (2.6 mg) in the form of the trifluoroacetate salt. MS m/z 364 [M+H]+.
