A New Synthesis of Pongachalcone I, Glabrachromene, Mixtecacin, Candidin, Atalantoflavone Dimethylether, Racemoflavone Dimethylether, and Dihydropyranoaurones, and Their Analogues

Treatment of substituted o-hydroxychalcones 1-3 with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone [DDQ] afforded a mixture of chromenochalcones 4-6 (pongachalcone I [5a], glabrachromene [5d]), aurones 7-9 and flavones 10-12. A new and convenient synthesis of candidin [17a], atalantoflavone dimethylether [17b], racemoflavone dimethylether [17d], mixtecacin [20a], and their derivatives via the corresponding unknown dihydropyranoflavanones 13-15 has also been described