Reaction Steps
(39 h) A mixture of 39 g-b (222 mg, 375 μmol) and 10% Pd/C (239 mg, 112 μmol) in MeOH (150 mL) was hydrogenated (50 psi) for 2 h. The mixture was filtered through diatomaceous earth (infusorial earth) and the filtrate was evaporated under vacuum to give (R*)-1-((1S*,2R*,4R*)-4-amino-2-(phenylsulfonylmethyl)cyclohexyl)-3-((2-(3-(trifluoromethyl)phenyl)-1,3-dioxolan-2-yl)methyl)pyrrolidin-2-one (39 h-b, 169 mg, 80%) as a white solid: 1H NMR (300 MHz, CDCl3) δ 7.87 (d, J=7.3 Hz, 2H), 7.68-7.35 (m, 7H), 4.22 (s, 1H), 4.02-3.60 (m, 5H), 3.50-3.14 (m, 4H), 2.80-2.63 (m, 1H), 2.60-1.60 (m, 12H); 19F NMR (282 MHz, CDCl3) δ −62.8; ESI MS m/z 567 [C28H33F3N2O5S+H]+. (39i) A mixture of 39 h-b (170 mg, 300 μmol), acetone (871 μL, 11.9 μmol), acetic acid (69.1 μL, 1.20 mmol), and sodium triacetoxyborohydride (255 mg, 1.20 mmol) in dichloroethane (17 mL) was stirred at room temperature for 2 h. The reaction was diluted with EtOAc (500 mL), washed with saturated NaHCO3 (3×150 mL), water (2×100 mL), and brine (150 mL), dried over Na2SO4, filtered, and evaporated. The residue was purified by CombiFlash chromatography (silica, 0-10% MeOH/CH2Cl2) to provide (R*)-1-((1S*,2R*,4R*)-4-(isopropylamino)-2-(phenylsulfonylmethyl)cyclohexyl)-3-((2-(3-(trifluoromethyl)phenyl)-1,3-dioxolan-2-yl)methyl)pyrrolidin-2-one (39i-b, 106 mg, 58%) as a white solid: 1H NMR (300 MHz, CDCl3) δ 7.89 (d, J=7.2 Hz, 2H), 7.68 (s, 1H), 7.64-7.39 (m, 6H), 4.20 (s, 1H), 4.05-3.90 (m, 2H), 3.81-3.60 (m, 3H), 3.48-3.11 (m, 4H), 3.10-2.88 (m, 1H), 2.60-2.10 (m, 5H), 2.09-1.60 (m, 8H), 1.43-1.00 (m, 6H); 19F NMR (282 MHz, CDCl3) δ −62.9; ESI MS m/z 609 [C31H39F3N2O5S+H]+. (39j) Compound 39i-b (103 mg, 168 pmol) and 37% formaldehyde (50 μL, 1.8 mmol) were dissolved in MeOH (2 mL) and stirred for 3 h at room temperature. Sodium cyanoborohydride (16 mg, 252 μmol) was added and the mixture was stirred for 2 h. The reaction was diluted with EtOAc (400 mL), washed with saturated NaHCO3 (3×150 mL) and brine (100 mL), dried over Na2SO4, filtered, and evaporated. The residue was purified by CombiFlash chromatography (silica, 0-10% CH2Cl2/MeOH) and then lyophilized from CH3CN/H2O to give title compound (77 mg, 74%) as a white solid: 1H NMR (300 MHz, CDCl3) δ 7.90-7.82 (m, 2H), 7.71 (s, 1H), 7.68-7.42 (m, 6H), 4.15-3.92 (m, 3H), 3.80-3.00 (m, 7H), 2.71-2.10 (m, 9H), 1.93-1.40 (m, 9H), 1.17-0.95 (m, 6H); 19F NMR (282 MHz, CDCl3) δ −62.9; ESI MS m/z 623 [C32H41F3N2O5S+H]+.
