Reaction Steps
(2S,3R,4R,5S,6R)-6-(acetoxymethyl)-3-(3-methylthioureido)-tetrahydro-2H-pyran-2,4,5-triyl triacetate (0.457 g, 1.09 mmol) was added to dry DCM, and SnCl4 (1.13 g, 4.33 mmol) was added dropwise. The reaction was stirred at room temperature overnight (16 h). The reaction was quenched with saturated aqueous NaHCO3 until the solution was basic and no more gas was evolved. The aqueous layer was extracted three times with DCM and the combined organic layers were dried with MgSO4, filtered and concentrated. The crude material was purified by flash chromatography (silica gel, EtOAc), providing (5R,6S,7R)-5-(acetoxymethyl)-2-(methylamino)-5,6,7,7a-tetrahydro-3aH-pyrano[3,2-d]thiazole-6,7-diyl diacetate (22) as an oil (0.30 g, 77% yield). 1H NMR (500 MHz, CDCl3) δ 2.05 (s, 3H), 2.06 (s, 3H), 2.08 (s, 3H), 2.90 (s, 3H), 3.84 (m, 1H), 4.12 (m, 2H), 4.34 (dd, 1H, J=4.3, 6.2 Hz), 4.90 (ddd, 1H, J=0.8, 2.8, 9.6 Hz), 5.39 (dd, 1H, J=2.9, 4.1 Hz), 6.21 (d, 1H, J=6.5 Hz). 13C NMR (125 MHz, CDCl3) δ 21.00, 21.10, 21.23, 31.19, 63.40, 68.67, 69.40, 72.24, 73.01, 90.03, 161.21, 169.72, 169.90, 170.89.
