Two new diphenyl ethers,
4-(2-carboxy-3-heptyl-5-methoxyphenoxy)-2-heptyl-6-hydroxybenzoic acid (micareic acid) (13),
4-(2-carboxy-3-heptyl-5-methoxyphenoxy)-2-heptyl-6-hydroxy-3-methoxybenzoic
acid (methoxymicareic acid) (27) and a new depside,
4-(2-heptyl-6-hydroxy-4-methoxybenzoyloxy)- 2-heptyl-6-hydroxybenzoic acid (prasinic acid) (34) have been detected in chemical races of
the lichen Micarea prasina
Fr. and isolated and characterized as the corresponding methyl esters. The
structure of the latter compounds has been confirmed by total synthesis. The
key steps in the synthesis of the diphenyl ethers (14), (26) involved Ullmann-like condensation between the 3-chloro 2-enone (17)
and the phenols (11), (31), and subsequent aromatization of the enol ethers (23) and (32). A biomimetic-type synthesis of
methyl micareate (48) has also been achieved by
treatment of the depside (33) with sodium hydride in dimethylformamide.
两种新的二苯醚、
4-(2-羧基-3-庚基-5-甲氧基苯氧基)-2-庚基-6-羟基苯甲酸(米卡里酸)(13)、
4-(2-羧基-3-庚基-5-甲氧基苯氧基)-2-庚基-6-羟基-3-甲氧基苯甲酸(甲氧基甲基苯甲酸) (13)
酸(甲氧基月桂酸)(27)和一种新的副产品、
4-(2-heptyl-6-hydroxy-4-methoxybenzoyloxy)- 2-heptyl-6-hydroxybenzoic acid(prasinic acid)(34)。
地衣中检测到了
并分离和鉴定出相应的甲基酯。后一种化合物的
后一种化合物的结构已通过全合成得到证实。合成
二苯醚 (14)、(26) 合成的关键步骤涉及 3-Cloro 2-enone (17) 与苯酚 (11)、(31) 之间的乌尔曼缩合反应。
和苯酚(11)、(31)之间的类似乌尔曼缩合,以及随后烯醇醚(23)和(32)的芳香化。仿生型合成
还通过
用氢化钠在二甲基甲酰胺中处理去氢化物 (33),也可以实现生物模拟型的缩甲醛甲酯 (48) 合成。