Synthesis of 11b-Hydroxy Erythrina Alkaloid, Erythrartine, and Its O-Acetate (Erythrascine?)

Oxidation of an erythrinan akaloid erysotramidine (4) with CAN in AcOH-MeCN gave, in moderate yield, the 11β-acetoxy derivative (5b), which was transformed into erythrartine (8). Its O-acetate (O-acetylerythrartine) was not identical with erythrascine in the 1 H-nmr spectra, presenting an ambiguity on the reported structure of erythrascine