Quinolizidines. XX. Racetnic and Chiral Syntheses of the Alangium Alkaloids 9-Demethylprotoemetinol and 10-Demethylprotoemetinol(Organic,Chemical)

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The synthesis of (±)-9-demethylprotoemetinol [(±)-3d] was accomplished by LiAlH_4 reduction of the tricyclic ester (±)-5 and subsequent debenzylation of the resulting tricyclic-alcohol (±)-10. Acetylation of (±)-3d with acetic anhydride and pyridine gave the diacetate (±)-11. The same sequence of reactions starting with (-)-5 afforded (-)-9-demethylprotoemetinol [(-)-3d] and the diacetate (-)-11 through (-)-10. Parallel synthetic routes starting with the isomeric tricyclic esters (±)-9 and (-)-9 produced (±)- and (-)-10-demethylprotoemetinols [(±)-4d and (-)-4d] and the corresponding diacetates [(±)-13 and (-)-13] through (±)-12 and (-)-12, respectively. The correctness of the structure and absolute stereochemistry of an Alangiutn alkaloid inferred to be 10-demethylprotoemetinol was confirmed by a direct comparison of its diacetate with synthetic (-)-13.
公益社団法人日本薬学会の論文
1987-07-25