A Chiral Synthesis of the Strychnos and Ophiorrhiza Alkaloid Normalindine

A full account of the first chiral synthesis of (−)-normalindine [(−)-4], an indolopyridonaphthyridine alkaloid isolated from Strychnos johnsonii and Ophiorrhiza filistipula, is presented. Central features of the synthetic strategy include the conversion of l-alanine methyl ester (13) into the oxazole derivative 12 and the intramolecular Diels–Alder reaction of the oxazole–olefin derivatives 27a and 30a. The correctness of the absolute configuration proposed for normalindine has been unambiguously confirmed by the present synthesis.