Exotine A, which comprises an unusual coumarin–cyclohepta[b]indole ring system, has been synthesized for the first time in a one-pot process from known starting materials. The key step features a biomimetically inspired combination of three components to deliver exotine A and 11′-epi-exotine A in 43% yield and 17:1 diastereomeric ratio. Some mechanistic aspects of this reaction are discussed.
包含不寻常香豆素-环庚[ b ]吲哚环系统的外泌素A,是通过已知原料从锅中首次合成的。关键步骤是仿生启发性地将三种成分组合在一起,以43%的收率和17:1的非对映异构体比例释放出exotine A和11'- epi- exotineA。讨论了该反应的一些机理方面。
Synthesis of the natural coumarins, murraol (CM-c2), trans-dehydroosthol and swietenocoumarin G
作者:Robert D.H. Murray、Saad Zeghdi
DOI:10.1016/0031-9422(89)85043-5
日期:——
Abstract The coumarin CM-c 2 , from Cnidium monnieri , 7-methoxy-8-(3-hydroxy-3-methylbut-1-enyl) coumarin, has been synthesized by palladium acetate-catalysed condensation of 7-methoxy-8-iodocoumarin with 2-methylbut-3-en-2-ol. Its stereochemistry follows from its conversion to trans-dehydroosthol. The identity of CM-c 2 and murraol has been established. Swietenocoumarin G has been prepared similarly
Pummeloquinone (1), the third example of a coumarin-naphthoquinone dimer from a natural source, was isolated form the roots of several hybrid seedlings resulting from a cross of May pummelo x Marsh grapefruit (Rutaceae) grown in an orchard at Okitsu, Shizuoka, and its structure was elucidated by chamical and spectrometric methods. Synthesis of 1 was also achieved by Diels-Alder reaction between trans-dehydroosthol (3) and 2-methoxy-1, 4-benzoquinone followed by 2, 3-dichloro-5, 6-dicyano-1, 4-benzoquinone (DDQ) oxidation.