Total synthesis of daphneticin, a coumarinolignoid.
作者:HITOSHI TANAKA、ICHIRO KATO、KAZUO ITO
DOI:10.1248/cpb.34.628
日期:——
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%。