Synthesis of Highly Dehydrogenated Oxoerythrinan Alkaloids, Erytharbine and Crystamidine_1,2)

2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) oxidation of 3,8-dioxoerythrinan-l(6)-enes in dioxane gave the ring B dehydrogenated products, the 1,6-dienones, while oxidation in benzene gave the fully dehydrogenated products, the 1,6,10-trienones. The same trienones were obtained by DDQ oxidation of the 1,6-dienones in bezene. On the contrary, oxidation of the isomeric enone, 3,8-dioxoerythrinan-1-ene, in either dioxane or benzene gave the ring C dehydrogenated product, the 1,10-dienone. The 1,6,10-trienones were transformed to the highly dehydrogenated 8-oxoerythrinan alkaloids, erytharbine and crystamidine, in racemic forms.