Alkaloids compounds

Synthesis of Alkaloidal Compounds Using an Electrochemical Reaction as a Key Step... 

The first example of this type of alkaloid, compound 535, known hitherto merely as 205B, has recently been isolated from the skin of the Panamanian frog Dendrobates pumilio. The absolute stereochemistry of the natural (—)-alkaloid was first established by the total synthesis of its (+)-enantiomer by a multistage route from the fused piperidine 536... 

The catalytic hydrogenation of enamide 34 in the presence of 0.5-1 mol% of (/ )-BINAP complex in a 5 1 mixture of ethanol and dichloromethane under 1-4 atm of hydrogen affords 35 with quantitative yield and higher than 99.5% ee. The (fi)-isomer is not reduced under similar reduction conditions. This approach provides a route to a number of alkaloid compounds (Scheme 6-19).47... 

Quinolizidine alkaloids are non-toxic to the legumes which produce them. On the other hand, the quinolizidine alkaloids can be toxic and in some cases very toxic to other organisms. The biotoxicity of alkaloids has for some time been considered to be connected with their bitter taste" ° ". The quinolizidine alkaloids are certainly bitter in taste to humans. However, not all alkaloids are. Literature states that some pyrrolizidine and indolizidine alkaloids are not bitter in their pure forms" Furthermore, there are many non-alkaloid compounds, such as flavonoids, that are bitter in taste but non-toxic. Therefore, although quinolizidine alkaloids are bitter, the connection between biotoxicity and bitter taste is not absolute. 

Codeine is one of 40 individual chemical compounds (specifically, alkaloid compounds) found in opium. Only a few of the opiate alkaloids are used medically the analgesics (painkillers) morphine... 

Opioid refers to any compound that acts like morphine, the most abundant alkaloid compound in opium. The term opioid includes substances that are derived from plants (such as morphine and codeine), those that occur naturally in the body (such as endorphins and enkephalins), and synthesized compounds (such as heroin and fentanyl). [Endorphins and enkephalins are discussed in Chapters 2 and 3. Fen-tanyi is discussed in Chapter 3.]... 

Most of the marine metabolites bearing a sulfide group correspond to well-defined families of alkaloid compounds and they have mainly been obtained from tunicates and sponges. To a lesser extent they have also been found in bryozoans, molluscs, and algae. 

Members of the group of natural, semisynthetic, or synthetic alkaloid compounds prepared from opium are referred to as opioids. This group includes natural compounds usually denoted opiates, such as morphine and codeine, and the synthetic and semi synthetic compounds such as oxycodone, buprenorphine, fentanyl, methadone, and tramadol. The pharmacological effects and pharmacokinetic parameters of these drugs share many common characteristics and are illustrated with the prototypic drug in this class, morphine. 

Therefore, this review is mainly devoted to the application of electroorganic reactions to the synthesis of some key skeletons which are commonly found in natural alkaloids and some key intermediates which are useful materials for the formation of alkaloidal structures. The synthesis of some other nitrogen heterocycles which are usually not found in alkaloidal compounds will not be part of this review even though the structures are highly interesting as targets in organic synthesis. 

Although the anodic generation of a cation in a-position to nigrogen in aliphatic amines is not difficult, this type of reaction is not always useful to the synthesis of alkaloidal compounds, since the cation is not stable and a simple dealkylation is the usual follow-up reaction. N-monomethyl and N,N-dimethylanilines are, however, useful starting materials for the synthesis of the skeleton of tetrahydroquinoline. The anodic methoxylation of N,N-dimethylaniline 20 takes place at the methyl group, and an iminium ion intermediate 22 is easily generated by treatment of the methoxylat-ed product 21 with Lewis add. This intermediate can be trapped in situ with a variety of nucleophiles such as electron-rich olefins yielding tetrahydroquinolines 23 16). 

Quinine is an alkaloid compound used to treat malaria and other feverish ailments. It is a product of the bark of the Cinchona tree, a large evergreen originally found in South America. The bark alone is called Peruvian bark, and is used in powdered form to treat fevers. 

The last alkaloid, compound L, named knightolamine (12), is closely related to (11) except for the lack of a carbonyl group in an acetyl ester and the presence of a benzoyloxy-group (1740 cm ) the parent ion (M+ 367 C HzsNOJ is cleaved to an ion of m/z 246 and a benzoyloxyl radical. The fragment of m/z 94 usually appears in the mass spectrum of those tropanes8 that have a hydroxy-group in the pyrrolidine moiety. 

Structural analogy with alkaloid compounds. One of these compounds, named quinizolate (13), exhibits an intense bitter taste at an extraordinarily low detection threshold of0.00025 mmol/kg of water. This novel taste compound was found to have 2000- and 28-fold lower threshold concentrations than the standard bitter compounds caffeine and quinine hydrochloride, respectively, and, therefore, it is claimed to be one of the most intensely bitter compounds reported so far [46]. It is important to note that in sensory evaluation there is a difference between detection threshold and recognition threshold the first determines the concentration of a substance that makes one able to say this is not pure water the second means that the panelist is able to state this is bitter. Therefore these reported data on the taste of new compounds must to be taken carefully especially in comparison with others. 

Ding, L. et al. Simultaneous determination of flavonoid and alkaloid compounds in citrus herbs by high-performance liquid chromatography-photodiode array detection-electrospray mass spectrometry. J. Chromatogr. B. 2007, 857, 202-209. 

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