To a stirred mixture of 2-((5aR,6R)-1-(4-fluorophenyl)-5a-methyl-5,5a,6,7,8,9-hexahydroimidazo[1,5-b]isoquinolin-6-yl)-1-methoxyethanol (Example 5a, 36 mg, 0.1 mmol), tert-butyl carbamate (35 mg, 0.3 mmol), triethylsilane (0.1 mL), and acetonitrile (0.5 mL) was added trifluoroacetic acid (0.03 mL). The mixture was stirred at RT for 40 hr. Concentration and purification using reverse phase HPLC (YMC S5 20×100 mm, 10 min. run, solvent A: 10% MeOH: 90% H2O: 0.1% TFA, solvent B: 90% MeOH, 10% H2O, 0.1% TFA) gave tert-butyl 2-((5aR,6R)-1-(4-fluorophenyl)-5a-methyl-5,5a,6,7,8,9-hexahydroimidazo[1,5-b]isoquinolin-6-yl)ethylcarbamate as a trifluoroacetic acid salt (23 mg, 0.043 mmol, 43% yield). MS found: (M+H)+=426.3.
