To a CH2Cl2 solution (0.2 M) of propyl ([7R]-7-amino-6,7,8,9-tetrahydro-pyrido[1,2-α]indo1-10-yl)acetate from Step 6 was added 4-fluorobenzenesulfonyl chloride (1.1 equiv.) followed by triethylamine (3 equiv.) and DMAP (1 equiv.). The reaction mixture was stirred for 12 h at rt. The mixture was concentrated under reduced pressure, diluted with EtOAc, and washed with aqueous NaHCO3, water and finally with brine. The organic layer was dried with Na2SO4, filtered and concentrated. The residue was purified by column chromatography on silica gel using a CombiFlashRF (Teledyne ISCO) eluting with EtOAc/Hex (10:90 to 50:50) to give the title compound (97%) as a colorless foam.
