Quinolizidines. XVII. A New Access to 9, 10-Dimethoxy- and 8-Hydroxy-9, 10-dimethoxybenzo [a] quinolizidine-Type Alangium Alkaloids from 3-Acetylpyridine

抄録

New syntheses of the ipecac and Alangium alkaloids possessing the 9, 10-dimethoxy- and 8-hydroxy-9, 10-dimethoxybenzo [a] quinolizidine skeletons (types 1 and 2) have now become possible through generally applicable routes starting from 3-acetylpyridine (5). The routes involve the mercuric acetate-edetic acid oxidation of the 3-acetylpiperidine derivatives 9a, b or the alkaline ferricyanide oxidation of the quaternary salts (26a, b and 27a, b) of 3-acetylpyridine equivalents, Wolff-Kishner reduction of the acetyl group or reductive desulfurization of the thioketal group, sulfenylation-dehydrosulfenylation of the lactams 12a, b, Michael reaction of the α, β-unsaturated lactams 15a, b, and de-ethoxycarbonylation of the Michael adducts 16a, b as the main operations.