23 エナミド光閉環反応による麦角アルカロイドの合成研究

概要

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Reductive photocyclization of enamides, which is carried out by the irradiation on an enamide in the presence of a large excess of sodium borohydride at low temperature, has been successfully applied to the synthesis of ergot alkaloids including lysergic acid, based on the preliminary study on the synthesis of some benzo(f)quinoline derivatives. A general synthetic route with a great potentiality of application toward a group of ergot alkaloids was established through the synthesis of some benzo(f)quinoline derivatives (16, 29, 33, and 35) which are regarded as the despyrrole analogs of ergot alkaloids. Reductive photocyclization of enamides (2, 10, and 22), prepared by acylation of 2-tetraloneimine (1) with methacryloyl, 3-methoxy-2-methylacryloyl, and 3-furoyl chlorides, afforded the skeletal structures of alkaloids in one step respectively, which were then structurally modified in order to introduce a double bond and/or functional groups in the ring C. Based on the synthetic route thus established, total synthetic works of ergot alkaloids were carried out using the tricyclic imine (5) as the common starting compound. As a result at the moment, total synthesis of 6,8-dimethylergolines and lysergic acid along with 2,3-dihydroagroclavine (21) and 2,3-dihydroisofumigaclavine (45) was achieved.
天然有機化合物討論会の論文
1982-09-10