In a 10 L four-necks round-bottom flask with mechanical stirring, add N-[(1S)-1-[4-[(4-tert-Butylpiperidin-1-yl)methyl]phenyl]-2,2,2-trifluoroethyl]methanesulfonamide (110.17 g, 0.27 mol) to isopropyl alcohol (3100 mL) at 16° C. with stirring. Add crystalline seeds of the phosphate (1.76 g) and the seeds persist in solution. Add a solution of phosphoric acid (2.1 eq, 31.33 mL) in isopropanol (2800 mL) to this solution over two hours. Off white precipitate forms. Then heat the mixture to 80° C. and stir for one hour. During this period a thick white slurry forms. Add more crystalline seeds (1.54 g) and stop the heating. Allow the mixture to reach 12° C. After 14 hours, filter the white slurry off and dry the wet white solid in vacuum oven at 60° C. for 16 hours to provide the title compound as a white solid (122 g, 89.2%). MS (m/z): 407 (M+1-HCl). [α]D20+12.6° (c=2.0, H2O).
