Reaction Steps
To N-((3aS,4R,6aR)-2-((R)-2-amino-4-methylpentanoyl)octahydrocyclopenta[c]pyrrol-4-yl)-2,2-dicyclohexylacetamide (0.133 g, 0.298 mmol) from Step B was added formaldehyde (0.228 mL, 2.98 mmol) in dichloromethane (0.5 mL). Acetic acid (0.5 mL) was added. The reaction was stirred at room temperature for 30 minutes, PS-cyanoborohydride (0.255 g, 0.597 mmol) was then added, and the reaction mixture was stirred at room temperature overnight. The reaction was filtered, and the solvent was removed in vacuo. The crude material was purified on silica gel chromatography on a silica gel cartridge (Analogix®, Burlington, Wis., RS-12) eluting with 1-10% methanol (2 N ammonia)/dichloromethane to give the title compound: 1H NMR (500 MHz, pyridine-d5) δ ppm 8.29 (dd, J=7.1, 15.9, 1H), 4.46-4.35 (m, 1H), 4.09-3.99 (m, 1H), 3.92-3.80 (m, 1H), 3.70 (dd, J=8.6, 12.4, 1H), 3.66-3.58 (m, 2H), 3.45 (dd, J=4.8, 9.1, 0.5H), 2.78-2.64 (m, 1H), 2.63-2.53 (m, 1H), 2.42 (s, 3H), 2.38 (s, 3H), 2.23-2.14 (m, 0.5H), 2.13-1.99 (m, 2H), 1.99-1.82 (m, 5H), 1.82-1.63 (m, 8H), 1.60 (d, J=14.0, 1H), 1.57-1.51 (m, 1H), 1.45 (ddd, J=8.6, 18.8, 29.3, 3H), 1.36-1.05 (m, 9H), 1.01 (d, J=6.6, 3H), 0.91 (dd, J=6.6, 19.9, 3H); MS (ESI+) m/z 474 (M+H)+.
