Reaction Steps
To a solution of Intermediate B (180 mg, 0.403 mmol) in dry THF (3 mL) was added a solution of 4-methoxybenzyl isothiocyanate (94%, 96 mg, 0.50 mmol) in dry THF (2 mL). The mixture was stirred at room temperature for 28 h. Solvents were evaporated under reduced pressure. The residue was dissolved in acetone (3 mL). MeI (114 mg, 0.805 mmol) was added. The mixture was stirred at room temperature for 2 h. Satd. aqueous NaHCO3 (2 mL) was added and stirred at room temperature for 10 min. The mixture was further diluted with satd. aqueous NaHCO3 (20 mL), extracted with EtOAc (2×15 mL). The combined extracts were washed with brine and dried over Na2SO4. Solvents were evaporated under reduced pressure. The crude product was purified by silica gel column chromatography, eluted with 96:3:1 EtOAc-MeOH—NH4OH (28% aqueous) to give rac-(3aS,4R,5R,6R,7aS)-4,5-bis(benzyloxy)-6-((benzyloxy)methyl)-N-(4-methoxybenzyl)-3a,4,5,6,7,7a-hexahydrobenzo[d]oxazol-2-amine (159 mg, 67%) as a syrup. 1H NMR (400 MHz, CDCl3) δ 7.37-7.25 (m, 15H), 7.21 (d, J=8.6 Hz, 2H), 6.81 (d, J=8.6 Hz, 2H), 4.80 (m, 1H), 4.79 (d, J=11.3 Hz, 1H), 4.77 (d, J=10.1 Hz, 1H), 4.66 (d, J=11.5 Hz, 1H), 4.45 (s, 2H), 4.44 (d, J=11.2 Hz, 1H), 4.35 (d, J=13.9 Hz, 1H), 4.25 (d, J=13.9 Hz, 1H), 4.07 (dd, J=7.9, 5.4 Hz, 1H), 3.76 (s, 3H), 3.64 (t, J=5.8 Hz, 1H), 3.56 (dd, J=10.2, 5.0 Hz, 1H), 3.51 (dd, J=8.2, 6.5 Hz, 1H), 3.47 (dd, J=9.1, 3.8 Hz, 1H), 2.17 (dt, J=14.7, 3.4 Hz, 1H), 2.06-1.97 (m, 1H), 1.88 (ddd, J=15.2, 12.1, 3.6 Hz, 1H).
