The hydroxyketoesters[3] were easily lactonized to the corresponding lactones[4] in excellent yields by the hydrolysis with aqueous alkali, followed by acidification. The present method was successfully applied to the syntheses of dihydrokawain[7c] and kawain[7d].
δ-羟基-β-
酮酯[3] 和 6-烷基-5, 6-二
氢-
4-羟基-2-
吡喃酮[4] 通过 TiCl4 促进的
双烯酮 [1] 与各种醛的加成获得 [4]。 2],然后用
酒精处理。通过用碱
水溶液
水解,然后酸化,羟基
酮酯 [3] 很容易内
酯化为相应的内
酯 [4],收率极好。该方法已成功应用于二
氢卡哇因[7c]和卡哇因[7d]的合成。