Reaction Steps
To a solution of (3aS,4R,5R,6R,7aS)-4,5-bis(benzyloxy)-6-((benzyloxy)methyl)-hexahydrobenzo[d]oxazol-2(3H)-one (237 mg, 0.500 mmol) in dry DCM (3.5 mL) was added 4 molecule sieves (200 mg) followed by trimethyloxonium tetrafluoroborate (370 mg, 2.50 mmol). The mixture was stirred under nitrogen at room temperature for 24 h. Pyrrolidine (355 mg, 5.00 mmol) was added followed by THF (2 mL). The mixture was stirred at room temperature for another 24 h. The mixture was 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 5% MeOH in DCM and then with 94:5:1 DCM-MeOH—NH4OH (28% aqueous) to give (3aS,4R,5R,6R,7aS)-4,5-bis(benzyloxy)-6-((benzyloxy)methyl)-2-(pyrrolidin-1-yl)-3a,4,5,6,7,7a-hexahydrobenzo[d]oxazole (54.5 mg, 21%) as a syrup. 1H NMR (400 MHz, CDCl3) δ 7.41-7.25 (m, 15H), 4.90 (d, J=11.7 Hz, 1H), 4.79 (d, J=11.2 Hz, 1H), 4.73 (d, J=11.7 Hz, 1H), 4.72 (m, 1H), 4.47 (s, 2H), 4.46 (d, J=11.2 Hz, 1H), 4.06 (dd, J=7.9, 5.4 Hz, 1H), 3.65 (t, J=5.9 Hz, 1H), 3.59 (dd, J=9.0, 5.2 Hz, 1H), 3.53-3.48 (m, 2H), 3.35 (t, J=6.6 Hz, 4H), 2.19 (dt, J=14.8, 3.3 Hz, 1H), 2.08-2.00 (m, 1H), 1.90-1.82 (m, 5H).
