75 触媒を利用するイソキノリン系アルカロイドの合成

概要

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In a course of isolation of diterpene alkaloids in Aconitum sp., we sometimes observe minor isoquinoline-type alkaloids which are a characteristic component of the primitive Angiosperms (e.g., magnoflorine (I), higenamine (II) etc.). This paper describes a simple two-step sequence involving the catalytic reaction of benzoins to benzylisoquinolines via benzyliden-4-oxo-isoquinoline skeletons. The method is a simple, convenient and economical method for the inversion of symmetrical or non-symmetrical benzoins to the known isoquinoline alkaloids by the use of few catalytic reactions. For example, 3,4,3',4'-Tetramethoxybenzoin obtaining by the benzoin condensation of veratraldehyde (E) gave 3', 4'-dimethoxybenzyliden-6,7-dimethoxy-4-oxo-isoquinoline (VI) by reaction with glycine in polyphosphoric acid (PPA). Then, VI was converted to tetrahydropapaverine (VII) by catalytic hydrogenation over Pd-C catalyst. Papaverine was obtained by the treatment of Pd-C in triglyme. We examined syntheses of (±)-laudanosine (VIII), takatonine (XIV), and (±)-reticuline (XVII) etc. These alkaloids can derive into several other alkaloids (e.g. aporphines, berbibes, pavines, and isopavines etc.). Especially, benzyl-4-hydroxy-tetrahydroisoquinolines(XX) are an important key compound of biogenetic-type synthesis and probably helpful in future chemotaxonomy in the primitive Angiosperms.
天然有機化合物討論会の論文
1979-09-20