Reaction Steps
Methanesulfonyl chloride (0.038 mL, 0.495 mmol) was added in portions to a stirred solution of tert-butyl ethyl(-(3aR,5R,6S,7R,7aR)-5-(hydroxymethyl)-6,7-bis((4-methoxybenzyl)oxy)-5,6,7,7a-tetrahydro-3aH-pyrano[3,2-d]thiazol-2-yl)carbamate (0.190 g, 0.323 mmol) in dry pyridine (5 mL) at −20° C. After 3 h, the reaction mixture was diluted with DCM (20 mL) and the DCM extract was washed with satd. NaHCO3, brine, dried over Na2SO4 and concentrated. Residual pyridine was removed by co-evaporation with hexanes. The crude product was purified by silica gel column chromatography (3:7 EtOAc/hexanes) to give (-(3aR,5R,6S,7R,7aR)-2-((tert-butoxycarbonyl)(ethyl)amino)-6,7-bis((4-methoxybenzyl)oxy)-5,6,7,7a-tetrahydro-3aH-pyrano[3,2-d]thiazol-5-yl)methyl methanesulfonate (0.215 g, 99.6%) as a white solid. 1H NMR (400 MHz, CDCl3) δ 7.32 (d, J=8.5 Hz, 2H), 7.17 (d, J=8.5 Hz, 2H), 6.91-6.83 (m, 4H), 6.01 (d, J=6.88 Hz, 1H), 4.66 (d, J=11.6 Hz, 1H), 4.60 (d, J=11.6 Hz, 1H), 4.52 (d, J=11.1 Hz, 1H), 4.42-4.36 (m, 2H), 4.27-4.23 (m, 3H), 3.96-3.84 (m, 2H), 3.8 (s, 3H), 3.79 (s, 3H), 3.55 (m, 2H), 2.98 (s, 3H), 1.52 (s, 9H), 1.20 (t, J=6.9 Hz, 3H).
