反应详情

The 3α-iodo derivative of 4,4-nor-methyl glycyrrhetinic acid, methyl ester is prepared by a method similar to that used by Greenhouse and Muchowski [Greenhouse, R., Muchowski, J. M., Can. J. Chem. 59 (1981) 1025-1027] (see Example 1). To a solution of 12.69 g (0.05 mole) of iodine in anhydrous benzene (35 mL) is added a solution of triphenylphosphine (13.12 g, 0.05 mole) in dry benzene (50 mL). After the solution becomes pale, an abundant yellow precipitate of triphenylphosphine diiodide is produced. To this solution is added directly 4,4-nor-methylglycyrrhetinic acid, methyl ester (9a) (4.56 g, 0.01 mole) and this suspension is heated to reflux with stirring for 22 hours. After cooling, the reaction mixture is mixed with ice-water (60 mL) and extracted. The benzene layer is further extracted with water (2×100 mL), dried over anhydrous sodium sulfate, evaporated and dried in vacuo to an off white solid. This residue is triturated with n-pentane (200 ml) and the insoluble triphenylphosphine oxide filtered. After rotary evaporation of the pentane solvent, the product is recrystallized from toluene:acetone.