Alkaloids, isoquinoline

Tropane alkaloids, isoquinoline alkaloids, indole alkaloids... 

B/sbenzylisoquinolins alkaloids isoquinoline alkaloids containing 2 fused benzylisoquinoline nuclei joined by one, two or three diaryl ether linkages. The ether linkages arise by phenol oxidation. B. a. occur in plants of the Menispermaceae and related families, which include the genera Berberis, Magnolia, Daph-nandra and Strychnos. 

Erythrina alkaloids isoquinoline alkaloids, usually tetracyclic, found exclusively in the legume genus Erythrina. 

M. is an - alkaloid and was first isolated in 1803 by F.W. Serturner by extraction from - poppy. M. is slightly soluble in hot water and chloroform but highly soluble in ethanol. It is the most important of the morphine alkaloids (isoquinoline alkaloids). A good grade of - opium contains between 9-14% of anhydrous morphine. 

Carbonylation of halides in the presence of primary and secondary amines at I atm affords amides[351j. The intramolecular carbonylation of an aryl bromide which has amino group affords a lactam and has been used for the synthesis of the isoquinoline alkaloid 498(352], The naturally occurring seven-membered lactam 499 (tomaymycin, neothramycin) is prepared by this method(353]. The a-methylene-d-lactam 500 is formed by the intramolecular carbonylation of 2-bromo-3-alkylamino-l-propene(354]. 

Replacing one carbon atom of naphthalene with an a2omethene linkage creates the isomeric heterocycles 1- and 2-a2anaphthalene. Better known by their trivial names quinoline [91-22-5] (1) and isoquinoline [119-65-3] (2), these compounds have been the subject of extensive investigation since their extraction from coal tar in the nineteenth century. The variety of studies cover fields as diverse as molecular orbital theory and corrosion prevention. There is also a vast patent Hterature. The best assurance of continuing interest is the frequency with which quinoline and isoquinoline stmctures occur in alkaloids (qv) and pharmaceuticals (qv), for example, quinine [130-95-0] and morphine [57-27-2] (see Alkaloids). 

Isoquinolines are used in catalytic (191), photographic (192), and dye appHcations (193). A great many alkaloids and synthetic medicinal compounds are isoquinoline derivatives. The principal dmgs containing this stmcture marketed in the United States are Hsted in Table 4. 

Noscapine [128-62-1] (45) is the second most abundant alkaloid found in opium. Unlike most opium alkaloids, however, it has an isoquinoline rather than a phenanthrene ting system. Noscapine was first isolated in 1817 but its antitussive activity was not demonstrated pharmacologically until 1952 (63). Clinical studies have confirmed its effectiveness. It is not a narcotic and has a wide margin of safety when given orally. Death could be produced in rats only with doses > 800 mg/kg (64). Noscapine is isolated from the water-insoluble residue remaining after processing opium for the manufacture of morphine. 

As exemplified in the present procedure, the reaction has been optimized and extended in scope it affords functionalized benzocyclobutenes as well as substituted isoquinolines in high yields. Benzocyclobutenes have been used as intermediates in the synthesis of many naturally occurring alkaloids, - steroids,polycyclic terpenoids,and anthracycline antibiotics. The traditional routes leading to the preparation of benzocyclobutenes have been... 

Isoquinoline Alkaloids" Academic Press New York, 1972 (e) Kametani, T. In "The Total Synthesis of Natural Products" ApSimon, J., Ed. Wiley-... 

Although, in most cases, iodine is a fairly inert halogen (in contrast to bromine) and does not normally react with the substances that have been chromatographed there are, nevertheless, examples where chemical changes have been observed. Oxidations can evidently take place (e.g. aromatic hydrocarbons and isoquinoline alkaloids [252,253]) and additions and substitutions have also been observed. Pale zones then appear on a brown background. 

Pyridine, pyrrole, quinoline, isoquinoline and indole alkaloids Apply sample solution and place the TLC plate in an iodine vapor chamber for 18 h, remove the excess iodine in a stream of warm air. Characterization on the basis of the iodination pattern. [53]... 

Quinoline, alkylquinolines, occurrence in Cusparia bark, 416 Quinoline group alkaloids, 413 isoQuinoline group alkaloids, 154 Quinolylphenetoledicarboxylic acid ex cinchonine, 441... 

Formally analogous to the foregoing Grignard additions are the intramolecular condensations of amides with aromatic systems, found in the Bischler-Napieralski reaction 101), which is of particular interest in isoquinoline and indole alkaloid syntheses (102). Condensations of amidines with reactive methylene compounds also led to enamines (103-106). 

The Bischler-Napieralski reaction involves the cyclization of phenethyl amides 1 in the presence of dehydrating agents such as P2O5 or POCI3 to afford 3,4-dihydroisoquinoline products 2. This reaction is one of the most commonly employed and versatile methods for the synthesis of the isoquinoline ring system, which is found in a large number of alkaloid natural products. The Bischler-Napieralski reaction is also frequently used for the conversion of N-acyl tryptamine derivatives 3 into p-carbolines 4 (eq 2). 

The Pictet-Spengler condensation has been of vital importance in the synthesis of numerous P-carboline and isoquinoline compounds in addition to its use in the formation of alkaloid natural products of complex structure. A tandem retro-aldol and Pictet-Spengler sequence was utilized in a concise and enantioselective synthesis of 18-pseudoyohimbone. Amine 49 cyclized under acidic conditions to give the condensation product 50 in good yield. Deprotection of the ketone produced the indole alkaloid 51. 

Carboline and isoquinoline alkaloids from marine organisms 96MI5. 

Dehydrodiscretamine (72), Thalifedine (73), Thalidastine (74), Fissisaine (75), Stepharanine (76), and Dehydrocorydahnine (77) are additional examples of alkaloids, which possess the 7-hydroxy-isoquinoline moiety which on deprotonation yields conjugated mesomeric betaines (Scheme 27). In either case, the rr-electron system is extended by substitution... 

Leptopinine 82 possesses the 3,4-dihydro-isoquinolin-7-ol moiety without further conjugation and was isolated as yellow powder from Hypecoum leptocarpum after several extractions with hydrochloric acid so that this alkaloid was finally isolated as a chloride (Scheme 29). The formation of a mesomeric betaine from this dihydroisoquinoline derivative is unlikely because on addition of base no significant changes of the UV spectra were observed (99P339). A similar structure is Pycnarrhine Pycnarrhena longifolia), which was isolated as a hydroxide (81P323). 

The aporphinoid alkaloid PO-3 (129) was also prepared by intermolecular benzyne cycloaddition between 1-methylene isoquinolines 148 and arynes derived from 147 (Scheme 53). The alkaloid was finally isolated by means of preparative thin layer chromatography (91JOC2984). 

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