Daphnetin (3) was transformed with excess benzyl chloride into 7, 8-dibenzyloxycoumarin (4), which on treatment with trifluoroacetic acid in benzene or aluminum chloride in benzene gave 8-benzyloxy-7-hydroxycoumarin (5) in good yield. Condensation of 5 and ethyl 2-bromo-3-(4-acetoxy-3, 5-dimethoxyphenyl)-3-oxopropionate (9), prepared from ethyl benzylsyringoylacetate (7) in two steps, in the presence of sodium hydride afforded 10 in good yield, and the condensation product (10) was then reduced with lithium borohydride to yield a mixture of the diols (11a, b). Treatment of the diols with 36% hydrochloric acid in acetic acid provided daphneticin (1) in 68% yield.
Daphnetin (3) 与过量的
氯化苄一起转化为 7,8-二苄氧基
香豆素 (4),用苯中的
三氟乙酸或苯中的
氯化铝处理后得到 8-苄氧基-7-羟基
香豆素 (5),收率很高。在氢化
钠存在下,将 5 与 2-
溴-3-(4-乙酰氧基-3, 5-二
甲氧基苯基)-
3-氧代丙酸乙酯 (9) (由苄基丁酰基
乙酸乙酯 (7) 分两步制备)缩合,得到 10,收率很好,然后用
硼氢化
锂还原缩合产物 (10),得到二元醇混合物 (11a, b)。然后用
硼氢化
锂还原缩合产物(10),得到二元醇混合物(11a、b)。用 36% 的
盐酸和
乙酸处理这些二元醇,得到
水飞蓟宾(1),收率为 68%。