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 dry DMF (1 mL) and sodium hydride (60% in mineral oil, 2.5 mg, 0.062 mmol) was added all in one portion. The mixture was stirred for 10 minutes at room temperature before 4-fluorobenzenesulfonyl chloride (12 mg, 0.062 mmol) was added. The reaction mixture was stirred for 10 minutes, and TFA (1 mL) was added dropwise. The reaction mixture was heated at 50° C. overnight and evaporated. The crude material was purified by preparative HPLC (ACE C8, 0.1% TFA-CH3CN) to give the title compound as a white solid (9.8 mg) in the form of the trifluoroacetate salt. MS m/z 381 [M+H]+.
