反应详情

Dihydropyrane (20.28 g; 241 mmoles) was dropped in 16 hrs into an ursodeoxycholic acid solution (30.0 g; 76.72 mmoles) and p-toluenesulphonic acid (1.55 g; 8.15 mmoles) in dioxane (160 ml), kept under magnetic stirring at room temperature. At the end of the addition the reaction mixture was concentrated under vacuum, taken up into ethyl ether (100 ml) then washed with water (3×50 ml) and saturated water (1×50 ml). After drying over sodium sulfate and evaporation of the solvents, the residue (45.00 g) was subjected to flash chromatography on SiO2 (φ=5 cm, h=20 cm): eluting with 95/5 chloroform/methanol, 34.4 g of compound (2) were obtained, (80%); νmax (CHCl3) 1710 cm-1 (C=O); 1H-NMR (CDCl3)δ 0,7 (s, 3H, 18-CH3); 0,9-1,0 (m, 6H, 19-CH3); 3,3-4,05 (m, 6H, 3-CH-, 7-CH-, 2x-OCH2); 4,4-4,7 (m, 2H, 2x-O-CH-O-).

1. additionAt the end of the addition the reaction mixture
2. concentrationwas concentrated under vacuum
3. washthen washed with water (3×50 ml) and saturated water (1×50 ml)
4. dry with materialAfter drying over sodium sulfate and evaporation of the solvents
5. washeluting with 95/5 chloroform/methanol