6 7 (67%) and heated to reflux for 1 h to effect the intramolecular cyclization. The resulting ketals were purified by chromatography on activity I11 neutral alumina and hydrolyzed with 5% aqueous acetic acid to give 5 (65% overall) and 7 (67% overall) after recrystallization. This chemistry demonstrated that both the B and C rings of the Erythrina skeleton could be formed via intramolecular cyclization. However, all attempts to hydrolyze the amide ...
