Reaction Steps
To a solution of tert-butyl ((3aR,5R,6S,7R,7aR)-6-(benzyloxy)-7-fluoro-5-((R)-1-hydroxyethyl)-5,6,7,7a-tetrahydro-3aH-pyrano[3,2-d]thiazol-2-yl)(methyl)carbamate (0.116 g, 0.264 mmol) and PMB (0.20 g, 1.3 mmol) in anhydrous DCM (6 mL) at −78° C. under N2, was added BCl3 (1.0 M in DCM, 1.2 mL, 1.2 mmol). The mixture was stirred for ˜3 h while the temperature of the cooling bath slowly warmed to room temperature. The reaction mixture was cooled at −78° C., quenched with mixed MeOH/DCM and then concentrated to dryness. The residue was purified on silica gel by flash column chromatography (1.0 M NH3 in MeOH/DCM, 1:10), affording (3aR,5R,6S,7R,7aR)-7-fluoro-5-((R)-1-hydroxyethyl)-2-(methylamino)-5,6,7,7a-tetrahydro-3aH-pyrano[3,2-d]thiazol-6-ol as a white solid (0.064 g, 97%). 1H NMR (400 MHz, CDCl3) δ 6.43 (dd, J=1.4, 6.5 Hz, 1H), 4.51 (ddd, J=3.2, 8.2, 48.2 Hz, 1H), 4.35-4.32 (m, 1H), 4.30-4.22 (m, 1H), 4.03-3.96 (m, 1H), 3.57 (d, J=8.2 Hz, 1H), 2.86 (s, 3H), 1.20 (d, J=6.3 Hz, 3H); 13C NMR (100 MHz, CD3OD) δ 164.40, 95.50 (d, J=183.3 Hz), 92.85 (d, J=8.6 Hz), 78.33 (d, J=6.2 Hz), 69.39 (d, J=20.8 Hz), 66.14 (d, J=16.5 Hz), 65.95 (d, J=8.4 Hz), 30.23, 20.71; MS, (ES, m/z) [M+H]+ 251.1.
