Reaction Steps
To a solution of 4B (57 mg, 0.158 mmol) in 5 mL of acetonitrile at rt was added DCC (33 mg, 0.158 mmol) followed by p-nitrophenol (44 mg, 0.317 mmol). The suspension was refluxed for 1 h, cooled to rt and filtered. The filtrate was concentrated under reduced pressure and the residue dissolved in EtOAc, washed with water and brine, dried (MgSO4), filtered and concentrated under reduced pressure. The residue was purified by flash chromatography (silica gel, EtOAc/Hexanes, 50:50 and 75:25) to afford the title compound (28 mg) as a beige solid. 1H NMR (DMSO-d6) δ 2.25, 2.28 (s, 3H), 2.31-2.38 (m, 2H), 3.46-3.50 (m, 1H), 3.86 (d, J=12.1, 1H), 4.24 (s, 1H), 4.93, 5.07 (d, J=7.2, 1H), 5.42, 5.51 (s, 1H), 7.27, 7.50 (d, J=8.2, 1H), 7.98, 8.03 (d, J=8.3, 1H); 13C NMR (DMSO-d6) δ 15.06, 15.74, 37.57, 60.55, 60.72, 64.84, 65.37, 68.30, 114.37, 115.61, 128.85, 129.59, 132.65, 132.79, 134.96, 136.96, 138.35, 139.36, 169.16; HPLC column: Phenominex LUNA C18 4.6×50 mm, 4 min gradient, 10% MeOH/90% H2O/0.1% TFA to 90% MeOH/10% H2O/0.1% TFA; 1 min hold, 4 mL/min UV detection at 220 nm, 2.62 min retention time; HPLC b) column: Shimadzu Shim-Pack VP-ODS C18 4.6×50 mm, 4 min gradient, 10% MeOH/90% H2O/0.1% TFA to 90% MeOH/10% H2O/0.1% TFA, 1 min hold; 4 mL/rein, UV detection at 254 nm, 2.45 min retention time (100%); HPLC c) column: Daicel Chiralcel OD 4.6×250 mm, Isocratic 25% Isopropanol/Hexanes, 30 min, 1 mL/min, UV detection at 220 nm, 12.65 min retention time (99%); MS (ES) m/z 340 [M−H]−.
