Structural and Synthetic Studies on Some B-Carboline Bases

Abstract

As a result of researches carried out on the roots of Rauwolfia seroentina in the 1930s, Siddiqui and Siddiqui reported the isolation of a series of new alkaloids, subsequent structural studies in which established them as β-carboline bases. One of these alkaloids which was later obtained in a pure form by the CIBA group of workers, namely reserpine, has found worldwide use as a hypotensive agent, and also in the treatment of mental aliments. The main alkaloid of R.serpentina roots which was named as Ajmaline is, on the other hand, finding extensive use in the treatment of cardiac arrhythmias of various origins and is being produced on a large scale by one of the German chemical firms. Ajmalicine, is also being used in combination along with reserpine for the treatment of high blood pressure (modinal). Again, mention must also be made here of the two main alkaloids of Peganum harmala, namely Harmine and Harmaline/Harmidine, both of which carry a β-carboline nucleus. Peganum harmala grows in great abundance in West Pakistan and contains about 5 to 7% total alkaloids in its seeds, but they have not so far found any significant commercial utilization. With the cheap availability of the β-carboline bases from plant sources it was consider worthwhile to carry out synthetic and structural studies on this interesting class of compounds with the aim of obtaining pharmacologically interesting substances for better utilization of the natural resources of the country. With this aim in view, the following work was completed in the last three years under the present project: a) Nitration studies on the β-carboline bases. b) Synthesis of new β-carbolines using Vilsmeier complexes. c) Conversion of harmine and harmaline into new derivatives. d) Isolation of new compunds from Rauwolfia vomitoria. e) Studies on the oil of Peganum harmala.