Abstract
A concise synthetic route leading to highly functional erythrina alkaloid skeletons has been developed. The key process is an oxidative carbon-carbon coupling followed by a conjugated addition. Based on this new strategy, a formal synthesis of demethoxyerythratidinone was completed in only 6 steps from 4-aminophenol.
Highlights
The genus Erythrina is widely distributed in tropical and subtropical regions and has been used in indigenous medicine.[1]
We reported the results towards the synthesis of analogues of erythrina alkaloids
E-mail: zhanghb@ynu.edu.cn; xdyang@ynu.edu.cn we speculated that a highly functional erythrina skeleton could be reached by a sequential oxidative dearomatization and a Michael addition
Summary
The genus Erythrina is widely distributed in tropical and subtropical regions and has been used in indigenous medicine.[1]. We tried the oxidation with (bis(trifluoroacetoxy)iodo) benzene (PIFA) in trifluoroethanol at 40 C.9 To our delight, this oxidation provided the desire azaspiro cyclohexyldienone (13), after treatment with DBU in dichloromethane, the desire intermediate (14) with a highly functional erythrina skeleton was obtained in 72% yield. This two steps procedure was soon optimized to be an efficient “one-pot” reaction: after the oxidative coupling, potassium carbonate was directly introduced to the reaction mixture at room temperature, and compound 14 was obtained in 83% isolated yield.
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