Indole continued structure

Centuries before the structure of indole was known, many of its derivatives were important commercial products. Ancient textile dyes and perfumes are but two of the markets described above in which indole has had a rich history. Indoles continue to impact both of these markets today. The use of indoles has expanded into facets of agriculture, animal health and the relatively new areas of dietary supplements and nutraceuticals. These are all commodity markets, distinct from the explosion of medicinal uses that have been discovered for indole-containing substances. 

Many names in common use for heteropolycycles provide little or no information about structure. Most such names were introduced long before any serious attempts were made to systematize nomenclature, and although more systematic equivalents can now be coined in many cases (for example, indole can be named benz[f)]azole or 1-azacyclopentabenzene), it is likely that the use of a substantial residue of trivial names will continue. However, one would not expect many new trivial names to be introduced in the future, except in the natural product area (see Section 1.02.4). 

The potential for transition metal complexes to provide new reactivity patterns continues to be explored by the preparation of complexes and the study of their reactivity patterns. The aminoalkyl substituents of gramine, tryptamine and methyl tryptophanate promoted metalation at C2 of the indole ring by Pt(DMSO)2Cl2. The crystal structure of the gramine product was determined. 

The extension of the use of lactams to include indolin-2-ones provides a Vilsmeier-type methodology for the construction of biindolyl systems, which are of considerable current interest.37,39-43 In this situation, the initially formed imines are indolenines, which readily isomerize to the related 2-indolyl derivatives.43 In view of our general interest in activated indoles, as well as a specific interest in continuing to synthesize structures containing indoles directly linked to each other, we investigated not only reactions with indolinone itself but also with substituted derivatives. These were variously methoxy-substituted at C-4 and C-6, and in some cases substituted also at C-3 with methyl, phenyl, or dithiolan groups. 

Interest in the mycotoxins of Aspergillus species continues, and the structures of several metabolites have been elucidated. Fumitremorgins A and B (FTA and FTB) are accompanied in A. fumigatus by six related indole-containing metabolites (FTC to FTH) which, however, appear to have no detectable tremorgenic properties. The first of these, FTC, exhibits very similar functionality and spectroscopic properties to tryptoquivaline, although the two compounds are not identical. However, FTC acetate and tryptoquivaline acetate (33) are identical hence FTC (34) differs from tryptoquivaline (35) solely in the position of the acetate group.31... 

Intermediate samarium enolates derived from ketones 1522 or 1525 could stereoselectively be trapped with allyl halides, leading to tricycles 1524 and 1526. The intramolecular alkylation by the chloroalkyl terminus of compound 1527 led to tetracyclic compound 1528 with satisfactory efficiency. These cascade reactions selectively generate three continuous stereogenic centers, including a quaternary carbon atom at the 3-position of the dihydroindole moiety, a structural motif of many indole alkaloids. 

On the basis of the examples reviewed above, it can be concluded that heterogeneous catalysis of the Fischer Indole Synthesis provides a practical and environmentally friendly alternative to the acids traditionally employed. Although it has not yet been possible to demonstrate unambiguously the use of a zeolite to effect the shape-selective formation of a single indole isomer, new structural types of zeolite and related materials continue to be synthesized, so that catalysts offering pore access and thus enhanced activity combined with shape selectivity remain a realistic research goal. 

Continuation of the French work on the alkaloids of F. difformis has led to the isolation of vellosimine ([aJu -f-56° in MeOH) which was identified by direct comparison and conversion to 10-deoxysarpagine (42). A second base, a 2-acyI indole, vincadiffine, obtained in a very small quantity (42), was assigned the structure, 3-oxo-4-methyl-3,4-secoaku-ammidine (IV), a deduction based on its NMR- and mass spectra (see Chart IV, and Chapter 2 of this volume). The configuration of C-16 substituents followed directly from the chemical shift of the ester-methyl 2.57 ppm (methyl-shielded by the aromatic group). 

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