Reactivity of isocoumarins. I. Effect of a neighboring hydroxyl group on the reduction of the lactone carbonyl group.
作者:MASATOSHI YAMATO、TADATAKA ISHIKAWA、TOMOHISA NAGAMATSU、SHIN YOSHIKAWA、TAKAJI KOYAMA
DOI:10.1248/cpb.28.723
日期:——
The reduction of 3, 4-dihydroisocoumarins (1, 3, 6, 11a, 11b, and 12b) having a hydroxyl group or acetoxyl group at the C(8)-position adjacent to the lactone carbonyl group with lithium aluminum hydride gave novel products, 1, 8-dihydroxyisochromans (10a, 13, and 16a), in addition to 8-hydroxyisochromans (2, 8, and 14) and 2-(3-hydroxy-2-hydroxymethylphenyl)-ethanols (4, 9, and 15). The isochromans and 2-(2-hydroxymethylphenyl)-ethanols are known reduction products of 3, 4-dihydroisocoumarins lacking a C(8)-hydroxyl group. In addition, 13 was obtained selectively in 50% yield by reduction of the magnesium chelate of 11a with lithium aluminum hydride. Similarly, 8-hydroxy-3-phenylisocoumarin (23a) and 8-acetoxy-3-phenylisocoumarin (23b) both gave 2-formyl-3-hydroxybenzyl phenyl ketone (24). Based on these results, a mechanism for the reduction of 8-hydroxy-3, 4-dihydroisocoumarins is proposed, as shown in Chart 3.
3, 4-二氢异香豆素(1, 3, 6, 11a, 11b 和 12b)中在C(8)位相邻乳糖羰基位置具有羟基或乙酰氧基的化合物,使用氢化铝锂进行还原,除了得到8-羟基异香豆素(2, 8, 和14)和2-(3-羟基-2-羟甲基苯基)乙醇(4, 9 和15)外,还获得了新颖的产品1, 8-二羟基异香烃(10a, 13 和16a)。已知的异香烃和2-(2-羟甲基苯基)乙醇是缺少C(8)-羟基的3, 4-二氢异香豆素的还原产物。此外,化合物13是通过使用氢化铝锂还原11a的镁螯合物而选择性获得,得率为50%。类似地,8-羟基-3-苯基异香豆素(23a)和8-乙酰氧基-3-苯基异香豆素(23b)均给出2-轭法尔-3-羟基苄基苯酮(24)。基于这些结果,提出了8-羟基-3, 4-二氢异香豆素还原的机制,如图表3所示。