Alkaloids indole family

The main emphasis of research on alkaloid biosynthesis has shown a significant move away from recently fashionable problems. The terpenoid indole family of alkaloids no longer dominates the scene and the benzylisoquinoline and ergot alkaloids have also lost their prominent position. 

The Indole Family. Tryptophan is also the precursor of another large alkaloid family based on the indole system. Usually, indole is found fused to other rings, as in physostigmine (3.22). Here, a pyrrolidine ting is fused to the b-face of indole. This alkaloid occurs in calabar beans. It is a potent inhibitor of cholinesterase, and like other such chemicals, it causes contraction of the pupil of the eye. In harmine (3.23), a pyridine ring is fused to the b-face. 

The order Gentianales (Apocynaceae, Gentianaceae, Lo-ganiaceae, Rubiaceae, and Theligonaceae) contains normal iridoid monoterpenes and secoiridoids, as well as iridoid-derived alkaloids in families other than the Asclepiadaceae. Multiple types of alkaloids are found in the Apocynaceae (indole and steroidal types), the Loganiaceae, and Rubiaceae (emetine, quinine, and indole types). 

The family Myristicaceae has about 16 genera and 380 species of tropical lowland rainforest trees that are easily recognizable in field collection because of their bloodlike sap, conical crown, and nutmeg-like fruits. A very interesting feature of Myristi-caeae species are their ability to elaborate series of neuroactive indole alkaloids, because it produces neuroactive indole alkaloids, which might hold potential for the treatment of anxiety, mood disorders, and other psychological disturbances. 

The family Zygophyllaceae is made up of 30 genera and 250 species of shrubs known to have the tendency to elaborate a series of serotonin-like psychedelic indole alkaloids such as harmine, harmol, and harmaline, notably found in the seeds of a medicinal... 

A fourfold anionic domino process consistingofadominoMichael/aldol/Michael/ aldol process was used by Koo and coworkers for the synthesis of bicyclo[3.3.1]non-anes. They employed 2 equiv. of inexpensive ethyl acetoacetate and 1 equiv. of a simple a, 3-unsaturated aldehyde [290]. Differently substituted dihydroquinolines were assembled in a Michael/aldol/elimination/Friedel-Crafts-type alkylation protocol by the Wessel group [291]. An impressive approach in this field, namely the construction of the indole moiety 2-557, which represents the middle core of the man-zamines, has been published by Marko and coworkers [292]. Manzamine A (2-555) and B (2-556) are members of this unique family of indole alkaloids which were isolated from sponges of the genus Haliclona and Pelina (Scheme 2.126) [293]. 

Scheme 2.126. Manzamine A (2-555) and B (2-556) - Members of a unique family of indole alkaloids.

Most botanists divide the plant family Apocynaceae into three subfamilies Plumerioideae, Cerberoideae, and Echitoideae. Alkaloids have been isolated from species belonging to all of these subfamilies however, indole alkaloids have been found only in the Plumerioideae. This subfamily is further divided into seven tribes, and indole alkaloids are present only in four of these, namely, Carisseae, Tabemaemontaneae, Alstonieae (Plumerieae), and Rau-wolfieae. 

Following Zenk s demonstration that strictosidine (33) is the key precursor of the indole alkaloids in a variety of plants in the family Apocyna-ceae, as well as several plants in other families, Battersby et al. 193) repeated experiments with both the 3a and 3p isomers of the primordial glucoside. The earlier results were not confirmed, for it was the 3a isomer which was specifically incorporated. Thus, the cycle of experiments is now complete for the involvement of strictosidine as the key intermediate in both enzyme systems and intact plants. 

Iminium ion-vinylsilane cyclizations closely related to the one described here have been used to prepare indolizidine alkaloids of the pumiliotoxin A and elaeokanine families, indole alkaloids, amaryllidaceae alkaloids, and the antibiotic (+)-streptazolin. The ability of the silicon substituent to control the position, and in some cases stereochemistry, of the unsaturation in the product heterocycle was a key feature of each of these syntheses. 

The quinolizidine structure is sometimes found in molecules of complex alkaloids belonging to the indole, isoquinoline, or other families of alkaloids that... 

A new halogen-containing member of the penitrem family of indole-diterpe-noids, which have insecticidal activity (1397), is thomitrem A (1466) from Penicil-lium crustosum (1398). The novel dichlorinated calmodulin inhibitor, malbrancheamide (1467), was characterized from the fungus Malbranchea auran-tiaca (1399). The microbe Streptomyces rugosporus produces pyrroindomycin B (1468), which is active against both methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococci (1400). The Chinese shrub Acacia confusa has yielded the unusual chlorotryptamine alkaloid 1469, which does not appear to be an artifactual dichloromethane adduct (1401). 

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