Reaction Steps
Compound 1 (47 g) in dry acetone (500 ml), K2CO3 (100 g) and dimethylsulphate (70 ml) were refluxed overnight. The white solid was filtered off, the filtrate concentrated, diluted with water and extracted with EtOAc. The EtOAc layer was washed with NaHCO3 solution and water, dried over anhydrous MgSO4. Removal of solvent afforded a straw coloured liquid, one spot by TLC, IR νmaxliq.film cm-1 : 1624; UV νmaxMeOH nm (ε): 296 (2875), 236 (2937), 217 (3027): 1H-NMR δ (CDCl3): 3.74 (3H, s, OCH3), 5.91 (2H, s, OCH2O), 6.31 (1H, dd, J=2.5, 8.5 Hz, H-5), 6.49 (1H, d, J=2.5, Hz, H-1), 6.70 (1H, d, J=8.5 Hz, H-4); HRMS m/z: 152.0473 (M+, 100, C8H8O3), 137.0238 (M+ --CH3, 88.42, C7H5O3). This methyl ether (40 g) in absolute THF (300 ml) at -10 C under argon gas was stirred with butyl lithium in hexane (100 ml, 1.1 mole) for 21/2 hrs. After the addition of BuLi the temperature of the reaction mixture was slowly raised to room temperature. Formation of the anion was confirmed by quenching an aliquot of the reaction mixture with D2O and observing the 1H=NMR (disappearance of the doublet signal at 6.49 ppm). The anion thus formed was stirred with dry DMF (20 ml) in THF (100 ml), at 0° C. (10 min) followed by refluxing (2 hrs). The reaction mixture was then acidified with HCL (6N) and extracted with ether (11/2 L). Drying over anhydrous MgSO4 and evaporation of the solvent afforded a pale yellow crystalline compound mp 124° C., IR νmaxKBr cm-1 : 1620, 1695, UV νmaxMeOH nm (ε): 211 (7811), 217.9 (7788), 268 (4536), 294.6 (2177): 1H-NMR δ (CDCl3): 3.81 (3H, s, OCH3), 6.07 (2H, s, OCH2O), 6.33 (1H, d, J=7 Hz, H-5), 6.88 (1H, d, J=Hz, H-4), 10.31 (1H, s, aldehyde); HRMS m/z: 180.0401 (M+, 100, C9H8O4), 165.0189 (M+ --CH3, 35, C8H5O4), 137.0238 (M+ --CH3CO, 45, C7H5O3).
