[Synthesis]
General procedure for the synthesis of 3-methoxy-4-(((2S,3R,4S,5S,6R)-3,4,5-trihydroxy-6-(hydroxymethyl)tetrahydro-2H-pyran-2-yl)oxy)benzaldehyde from 4-O-(2',3',4',6'-tetraoxo-acetyl-Β-D-glucopyranoside) vanillin: 2,3,4,6-tetra-O- vanillin 2,3,4,6-tetra-O- acetyl-β-D-glucopyranoside (1.36 g, 3.0 mmol) was dissolved in a solvent mixture of THF/CH3OH/H2O (33 mL, 5:5:1, v/v), followed by the addition of K2CO3 (0.83 g, 6.0 mmol). The reaction mixture was stirred at 40 °C for 20 min before the reaction was quenched with 1 M HCl solution and subsequently concentrated. The residue was purified by silica gel column chromatography (eluent CH2Cl2/CH3OH, 15:1, v/v) to afford the target product 4 as a white solid (0.88 g, 94% yield). The specific optical rotation of the product was [a]D20 -11.4 (c 1.0, H2O).1H NMR (DMSO-d6, 400 MHz) δ: 9.86 (s, 1H, CHO), 7.52 (dd, J = 8.3, 1.5 Hz, 1H, Ph-H), 7.43 (d, J = 1.4 Hz, 1H, Ph-H), 7.28 (d, J = 8.4 Hz, 1H, Ph-H), 5.39 (d, J = 4.4 Hz, 1H, -OH), 5.16 (d, J = 3.7 Hz, 1H, -OH), 5.09 (d, J = 5.2 Hz, 2H, -OH, H-1), 4.59 (t, J = 5.6 Hz, 1H, -OH), 3.84 (s, 3H, -OMe). 3.66 (dd, J = 11.2, 4.7 Hz, 1H, H-3), 3.48-3.45 (m, 1H, H-2), 3.40-3.37 (m, 1H, H-4), 3.30-3.25 (m, 2H, H-6), 3.20-3.14 (m, 1H, H-5).13C NMR (DMSO-d6, 150 MHz ) δ: 191.66 (CHO), 151.78, 149.34, 130.56, 125.43, 114.58, 110.52, 99.41 (C-1), 77.17, 76.84, 73.11, 69.58, 60.62, 55.70. ESI-HRMS m/z [M+Na]+ calculated value C14H18NaO8 was 337.0894 and the measured value was 337.0901. |