(-)-Podorhizol (1) was stereoselectively synthesized by erythro preferential aldol condensation of 3,4,5-trimethoxy- benzaldehyde with potassium enolate from (+)-(R)-3- (3,4-methylenedioxybenzyl)-4-butanolide (2) (erythro:threo=85:15). Erythro selectivity was observed in the aldol condensation of many alkoxybenzaldehydes with potassium enolate from (+)-γ-butyrolactone 2. However, benzaldehydes having methoxy groups at both the 2 and 6 positions gave threo selectivity in the aldol condensation with potassium enolate from (+)-γ-butyrolactone 2.
(-)-Podorhizol (1) 是通过
3,4,5-三甲氧基苯甲醛与来自 (+)-(R)-3-(3,4-二氧基苯甲基)-4
-丁内酯 (2) 的
钾烯醇进行红脆优先的醇缩合反应立体选择性合成的(红脆:反式=85:15)。在许多烷氧基
苯甲醛与来自 (+)-
γ-丁内酯 2 的
钾烯醇的醇缩合反应中观察到了红脆选择性。然而,具有在 2 和 6 位均为甲氧基取代基的
苯甲醛在与来自 (+)-
γ-丁内酯 2 的
钾烯醇的醇缩合反应中则表现出反式选择性。