Reaction Steps
The thiourea from above (200 mg, 0.32 mmol) was dissolved in CH2Cl2 (4 mL) and SnCl4 (0.5 mL, 4.0 mmol) was added. Then the resulting mixture was stirred at room temperature for 16 h. The solution was diluted saturated aqueous NaHCO3 (20 mL), then the resulting mixture was extracted with CH2Cl2 (3×10 mL) and the combined organic extracts were dried (Na2SO4) and concentrated. Flash chromatography of the residue (EtOAc:hexanes 2:3) gave (3aR,5R,6S,7R,7aR)-5-(acetoxymethyl)-2-(((9H-fluoren-9-yl)methoxy)carbonylamino)-5,6,7,7a-tetrahydro-3aH-pyrano[3,2-d]thiazole-6,7-diyl diacetate as a pale colourless foam (125 mg, 69% yield). 1H NMR 500 MHz, CDCl3) δ 1.88 (s, 3H), 2.04 (s, 3H), 2.12 (s, 3H), 3.69 (m, 1H), 3.81 (ddd, 1H, J=2.5, 5.5, 6.5 Hz), 4.12 (dd, 1H, J=2.5, 12.5 Hz), 4.21-4.26 (m, 2H), 4.55 (dd, 1H, J=6.0, 12.5 Hz), 4.72-4.75 (dd, 1H, J=6.5, 6.5 Hz), 4.95 (dd, 1H J=5.5, 9.5 Hz), 5.24 (dd, 1H J=6.5, 9.5 Hz), 6.01 (d, 1H, J=6.5 Hz), 7.35 (dd, 2H, J=7.1, 7.8 Hz), 7.44 (dd, 2H, J=7.0, 7.8 Hz), 7.59 (d, 2H, J=7.1 Hz), 7.81 (d, 2H, J=7.0 Hz). 13C NMR (125 MHz, CDCl3) δ 20.62, 20.71, 21.35, 46.78, 57.91, 63.70, 67.92, 69.46, 71.88, 72.52, 90.23, 120.71, 120.89, 123.83, 124.04, 125.15, 127.76, 127.97, 129.61, 129.72, 130.08, 141.31, 142.86, 152.11, 161.43, 169.11, 169.63, 170.23.
