Reaction Steps
To a solution of phenyl 3-azido-4-O-benzoyl-3,6di-deoxy-1-thio-β-L-galactopyranoside (β-18) (118 mg, 0.307 mmol) in 5 mL of CH2C2 is added TEA (256 μL, 1.87 mmol), pivaloyl chloride (114 μL, 0.921 mmol) and DMAP (19 mg, 0.154 mmol). The reaction mixture is stirred at room temperature for 12 h, diluted with 15 mL of CH2Cl2, washed with 1M HCl (2×10 mL), dried over Na2SO4, filtered and concentrated. The crude product is purified by flash chromatography (20% EtOAc/petroleum ether) to give 114 mg (80%) of phenyl 3-azido-4-O-benzoyl-3,6-di-deoxy-2-O-pivaloyl-1-thio-β-L-galactopyranoside (β-19): Rf 0.54 (20% EtOAc/petroleum ether); 1H NMR (CDCl3, 270 MHz) δ 7.93 (d, 2H, ArH), 7.59-7.56 (m, 3H, ArH), 7.46-7.26 (m, 5H, ArH), 5.53 (d, J=2.6 Hz, 1H, H-4), 5.25 (t, J=9.9 Hz, 1H, H-2) 4.73 (d, J=9.9 Hz, 1H, H-1), 3.92 (q, J=6.3 Hz, 1H, H-5), 3.79 (dd, J=2.6, 9.9 Hz, 1H, H-3), 1.42-1.21 (m, 12H, H-6, CH3); 13C NMR (CDCl3, 68 MHz) δ 176.8, 165.9, 133.8, 133.7, 131.8, 130.2, 129.0, 128.9, 128.6, 128.4, 86.1, 74.4, 71.6, 68.3, 63.9, 39.1, 27.3, 16.9; FAMS C24H27O5N3 (MNa+) calcd 492.1569, found 492.1579.
