Acid-Catalysed Epimerization of Reserpine and Other Indolo(2,3-a)QuinolizidineDerivatives

摘要

Information about the mechanisms involved in the acid-catalyzed epimerizationreaction of indole alkaloid analogues was sought by subjecting reserpine and other indolo(2,3-alpha)quinolizidines to strongly acidic conditions (trifluoroacetic acid). The essential role of the N(sub alpha) lone pair in the epimerization reaction was demonstrated by the failure of N(sub alpha) lactams to epimerize under acidic conditions. In fact, the necessity of the whole aromatic pi system was demonstrated through the introduction of deactivating substituents to the aromatic A ring.