To a solution of methyl 14-cyclohexyl-3-fluoro-7-oxo-5,6,7,8-tetrahydroindolo[2,1-a][2,5]benzodiazocine-11-carboxylate (from Step 4) in THF (0.02 M), BH3.THF (5 eq, 1 M solution in THF) was added and the solution stirred at RT for 2 h. MeOH (0.02 M) and a 1.25 M solution HCl in MeOH (0.24 M) were added carefully and left overnight to stir at RT before reducing the volume of the volatiles in vacuo and diluting with EtOAc. The organic phase was washed with aqueous NaHCO3 solution and brine, before being dried over Na2SO4, filtered and the solvent evaporated in vacuo to afford the title compound. The crude was used in the next step without further purification (quant); MS (ES+) m/z 407 (M+H)+.
