1. For a recent summary seeR. Robinson,The Structural Relations of Natural Products (Oxford at the Clarendon Press, 1955), p. 100.
2. W. I. Taylor, J. Amer. chem. Soc.79, 3298 (1957).
3. It is already known that voacangic acid suffers decarboxylation in acidic media to furnish ibogaine [M.-M. Janot andR. Goutarel, C. R. Acad. Sci. Paris241, 986 (1955)]. Compare the analogous decarboxylation of 2-substituted 2-carboxy-β-carbolines [G. Hahn, L. Bärwald, O. Schales, andM. Werner, Ann.520, 107 (1935)].
4. R. Goutarel, F. Percheron, andM.-M. Janot, C. R. Acad. Sci. Paris243, 1670 (1956).
5. R. Goutarel andM.-M. Janot, C. R. Acad. Sci. Paris242, 2981 (1956).