Reaction Steps
4-Methoxyphenyl 3-O-benzyl-2-O-levulinoyl-α-D-fucopyranoside (6) (971 mg, 2.12 mmol) was azeotroped 2 times with toluene and dissolved in 20 mL of dichloromethane. Pyridine (1.84 g, 1.87 mL, 23.3 mmol) was added and the mixture cooled to 0° C. Triflic anhydride (1.19 g, 0.71 mL, 4.24 mmol) was added and the mixture stirred for 90 min at 0° C. The mixture was quenched by addition of diluted NaHCO3 solution, the phases were separated and the organic layer extracted 3 times with 3% hydrochloric acid, once with water, dried over Na2SO4 and was concentrated. The resulting crude product was azeotroped 3 times with toluene to remove all traces of pyridine and dried for 1 h in vacuo. The yellow product was dissolved in 25 mL of DMF and sodium azide (3.58 g, 55.1 mmol) was added, and the reaction mixture stirred overnight. The mixture was diluted with water and EtOAc, the phases were separated. The organic phase was washed 3 times with brine, dried over Na2SO4 and concentrated. Column chromatography (3:1 hexane/EtOAc) afforded 816 mg (80%, 2 steps) of 7 as a slightly yellow oil: [α]D: +192.6 (c=1.25, CHCl3). IR (thin film, CHCl3): 3015, 2103, 1739, 1713, 1503, 1400, 1359, 1159, 1034 cm−1. 1H NMR (CDCl3, 300 MHz) δ 1.31 (d, J=6.3 Hz, 3H), 2.14 (s, 3H), 2.58 (m, 2H), 2.69 (m, 2H), 3.26 (t, J=9.9 Hz, 1H), 3.77 (s, 3H), 3.83 (m, 1H), 4.08 (m, 1H), 4.84 (d, J=10.8 Hz, 1H), 4.90 (d, J=10.8 Hz, 1H), 4.96 (dd, J=9.9 Hz, J=3.6 Hz, 1H), 5.48 (d, J=3.3 Hz, 1H), 6.83 (d, J=9.0 Hz, 2H), 6.99 (d, J=9.0 Hz, 2H), 7.31-7.42 (m, 5H). 13C NMR (CDCl3, 75 MHz). 18.4, 28.0, 29.8, 37.8, 55.7, 66.8, 67.9, 73.6, 75.4, 76.6, 78.1, 95.7, 114.6, 118.2, 127.8, 127.8, 128.3, 137.8, 150.4, 155.2, 171.9, 205.7. MALDI-HRMS: m/z [M+Na]+ calcd 506.1898, obsd 506.1889.
