To a solution of N1-[(2R,3S)-3-amino-2-hydroxy-4-phenylbutyl]-N1-(cyclopentyloxy)-4-methoxy-1-benzenesulfonamide×trifluoracetic acid (Step 1, Example 48), (50 mg, 0.091 mmol) in approximately 1.5 mL of dichloromethane under Argon was added benzylchloroformate (15.6 μL, 0.109 mmol) followed by N,N-diisopropylethylamine (47.9 μL, 0.273 mmol). After stirring 18 hours, the reaction mixture was evaporated in vacuo to a residue and purified on a preparative silica gel TLC plate (20×20 cm, 1000 μM) eluting with 95:5 methylene chloride:methanol. The product band was removed, eluted with 4:1 methylene chloride:methanol, filtered, and evaporated in vacuo. The residue was partitioned between dichloromethane and water. The organic layer was separated, dried over anhydrous magnesium sulfate, filtered, and evaporated in vacuo. The residue was lyophilized from acetonitrile and water to provide phenylmethyl N-((1S,2R)-1-benzyl-3-(cyclopentyloxy)[(4-methoxyphenyl)sulfonyl]amino-2-hydroxypropyl)carbamate (37 mg, 71%). H1-NMR (methanol-D4) 1.71 (m, 8H), 2.59 (m, 1H), 2.93 (m, 2H), 3.10 (m, 1H), 3.81 (m, 2H), 3.83 (s, 3H), 4.86 (m, 3H), 7.06 (m, 2H), 7.21 (m, 10H), 7.73 (m, 2H). MS(ESI): 591 (M+Na).
