Key Laboratory of Forest Plant Ecology, Ministry of Education, Northeast Forestry University, Harbin 150040, China.
Molecules. 2013 Dec 13;18(12):15613-23. doi: 10.3390/molecules181215613.
In this article we describe a new methodology for the total synthesis of 3,4-unsubstituted coumarins from commercially available starting materials. Six examples were prepared, including five naturally occurring coumarins--7-hydroxy-6,8-dimethoxy-coumarin (isofraxidin), 7-hydroxy-6-methoxycoumarin (scopoletin), 6,7,8-trimethoxy-coumarin, 6,7-dimethoxycoumarin (scoparone), and 7,8-dihydroxycoumarin (daphnetin) and one synthetic coumarin, 7-hydroxy-6-ethoxycoumarin. Moreover, five important o-hydroxybenzaldehyde intermediates were also obtained, namely 2,4-dihydroxy-3,5-dimethoxybenzaldehyde, 2,4-dihydroxy-5-methoxybenzaldehyde, 5-ethoxy-2,4-dihydroxy-benzaldehyde, 2-hydroxy-3,4,5-trimethoxybenzaldehyde, and 2-hydroxy-4,5-dimethoxy-benzaldehyde. The method developed herein involves just three or four steps and allows for the rapid synthesis of these important molecules in excellent yields. This is the first synthesis of 6,7,8-trimethoxycoumarin and 7-hydroxy-6-ethoxycoumarin.
在本文中，我们描述了一种从商业可得的起始原料全合成 3,4-未取代香豆素的新方法。制备了六个实例，包括五个天然香豆素——7-羟基-6,8-二甲氧基香豆素（异弗罗定）、7-羟基-6-甲氧基香豆素（东莨菪内酯）、6,7,8-三甲氧基香豆素、6,7-二甲氧基香豆素（scoparone）和 7,8-二羟基香豆素（瑞香素）以及一个合成香豆素 7-羟基-6-乙氧基香豆素。此外，还获得了五个重要的邻-羟基苯甲醛中间体，分别为 2,4-二羟基-3,5-二甲氧基苯甲醛、2,4-二羟基-5-甲氧基苯甲醛、5-乙氧基-2,4-二羟基苯甲醛、2-羟基-3,4,5-三甲氧基苯甲醛和 2-羟基-4,5-二甲氧基苯甲醛。所开发的方法仅涉及三到四个步骤，并允许以优异的收率快速合成这些重要的分子。这是 6,7,8-三甲氧基香豆素和 7-羟基-6-乙氧基香豆素的首次合成。
