Ein Übergang aus der Strychnin‐ in die Heteroyohimban‐Reihe der Indolalkaloide durch oxidative Umlagerung von Isostrychninsäure

A Transformation from the strychnine into the Heteroyohimbane Series of the Indole Alkaloids by Oxidative Rearrangement of Isostrychnic Acid By peroxyacid oxidation of isostrychnic acid there are formed, together with the amine oxide of base 2, three isomeric lactone bases, C21H20N2O4, which are formulated as 3–5. Reduction of the isatogen 5 leads to ring opening on both sides of the indole nitrogen (6, 7), and hydrochloric acid introduces a chloro atom in p‐position to the nitrogen (9). – Both tautomeric forms of 2 can be fixed by reduction to 8 and 10, respectively. – The lactone ring of 2 is hydrolyzed by hot dilute hydrochloric acid, followed by rearrangement to the heteroyohimbane type indoloquinolizidine 12. Compound 12, featuring as keto‐enol and amino acid, can be reduced and cyclised with mineral acid to the lactone 14 (two diasteroisomers) serving for X‐ray structural analysis. Treatment of 12 with acetic anhydride afforded the lactone 20 by rearrangement of the double bonds. Further hydrogenation products of 12 are described (15, 16, 18) and their spectra, including mass and CD spectra, are discussed. Biochemical implications are referred, too.