Showing papers on "Indole alkaloid published in 1968"

Über das alkaloid Eripin aus Hunteria umbellata. 128. Mitteilung über Alkaloide [1]

Abstract: Eripine, a new indole alkaloid, was isolated from the leaves of Hunteria umbellata. The spectral data of the alkaloid, of eripinic acid and the O-acetyl and 19, 20-dihydro derivatives of the alkaloid led to the structure II. Heating of II gave a mixture (ratio 3,5:1) of the known alkaloid erinine (I) and its stereoisomer, isoerinine (VII), which is not found in nature. The same mixture was obtained on heating either erinine or isoerinine.

Chapter 1 The Distribution of Indole Alkaloids in Plants

Abstract: Publisher Summary Alkaloids are most widely distributed among flowering plants and rarely occur in animals, simple vascular plants, mosses, ferns, fungi, and algae. Indole alkaloids are no exception to this general observation. Tryptophan is recognized as a main constituent of plant proteins and as a common biogenetic precursor of the complex indole alkaloids; hence, the wide occurrence of tryptamine derivatives in the plant kingdom is not unexpected. The majority of the simple indole alkaloids are confined to the dicotyledon plants. It is reasonable then that the complex indole alkaloids also mainly inhabit the dicotyledones. The dimeric complex indole alkaloids are coded simply on the basis of the two monomeric types that are a part of their architecture. In this manner, no complete structural definition as to their exact interactions is possible, but at least their probable biogenetic origin may be readily recognized. The tryptamine unit is easily recognized in the ergot alkaloid. Experiments have shown tryptophan to be a precursor. The recent discoveries of ergot derivatives in Aspergillus and Rhizopus, as well as in several species of the Convolvulaceae family, indicate that they may be more widely distributed in flowering plants than originally envisaged. This indication together with the fact that tryptophan and mevalonic acid have been shown to be precursors in both Claviceps and Convolvulaceae species point to the future necessity of accepting the ergot group as representing yet another complex indole alkaloid type.

Simple Amino Acid Derivatives and Protoalkaloids

Abstract: A number of naturally occurring nitrogen compounds have basic properties in common with the alkaloids but are usually not classified as alkaloids because their structures are relatively simple. Their nitrogen atoms are not incorporated into heterocyclic skeletons; and they are seen to be derivable from amino acids by a few, simple reactions. Mere decarboxylation of amino acids produces simple amines which are never classed as alkaloids. Further modification of such simple amines by the introduction of methyl groups or hydroxyl groups or both gives rise to a group of ambiguously classified compounds that are sometimes called alkaloids. However, it seems useful to distinguish them by the name “protoalkaloids,” suggesting both their simple structures and their possible role as precursors of more typical alkaloids (cf. Chap. 1).

Chapter 4 The Iboga and Voacanga Alkaloids

Abstract: Publisher Summary Iboga alkaloids originate from tryptophan or its equivalent and two mevalonate residues. The latter are linked head-to-tail because geraniol can also function as a precursor of the hydroaromatic portion. These results along with the incorporation of the same precursors in other indole alkaloids confirm the earlier hypothesis that was based solely on the classic method of recognizing similar units within apparently dissimilar natural products. The true complexity of basic extracts and the distribution of individual alkaloids began to be recognized when alkaloid mixtures from apocynaceous plants were looked into. Of the three major indole alkaloid classes, the iboga system appears to have the narrowest distribution. Among the new alkaloids, kisantine was originally isolated in minute quantity from Tabernanthe iboga Baillon and it was not until its nuclear magnetic resonance (NMR) and mass spectrum were measured that it was found to be ibogaline oxindole. Gabonine, on the other hand, is a dimer according to the mass spectrum and on the basis of the other data, its structure has been used as a working hypothesis.