Alkaloid lignan

A broad range of biaryl structures, as is often encountered in various classes of naturally occurring compounds, such as alkaloids, lignans, and tannins, can be prepared by oxidative arylic coupling. Oxidative couplings have also been used to build non-natural skeletons, such as the binaphthol derivatives that play an important role in asymmetric synthesis. 

Of phenolic oxidations using vanadium compounds, intramolecular oxidative phenolcoupling reactions are quite attractive from the viewpoint of natural products synthesis. A number of benzylisoquinoline alkaloids, lignans and neolignans are well known to be produced, in a key step, by oxidative radical coupling of open phenolic precursors. 

A lot of anticancerous agents have been isolated from natural sources especially from microorganisms and plants. However, there is no one special type of compound for cancer therapy various types of substances are effective for various types of cancers and tumors, for instance, alkaloids, lignans, terpenes and steroids [1]. In this report, concentrates on those antitumor compounds isolated from higher plants. 

Biaryl structures are wide-spread in many of naturally occuring products including alkaloids, lignans, terpenes, flavonoids, tannins, as well as polyketides, coumarins, peptides, glycopeptides, etc. For example, vancomycin (1) is a basic structure of several related glycopeptide antibiotics [1] balhimycin, actinoidin A, ristocetin A, teicoplanin A2-2, complestatin, etc which are important in medicinal chemistry or as a HPLC chiral stationary phases (vancomycin) [2]. 

Khalid S A, Waterman P G 1981 Alkaloid, lignan and flavonoid constituents of Haplophyllum tuberculatum from Sudan. Planta Med 148-152... 

Nawwar MAM, Barakat H H, Buddrus J, Linscheid M 1985 Alkaloidal, lignan and phenolic constituents of Ephedra alata. Phytochemistry 24 878-879... 

Examples of inhibitors of chromatin function derived from flowering plants (Fig. 80) are etoposide (lignan) and alkaloids camptothecin, Vinca alkaloids, and 7 epitaxol. The rhizome of Podophyllum peltatum L. (May apple, Berberidaceae) has been used to remove warts and to relieve the bowels from costiveness since very early times. It contains podophyllo-toxin, a cytotoxic lignan from which etoposide (Vepesid ), which is used to treat lung cancer, lymphomas, and leukemias on account of its ability to inhibit the activity of... 

Podophyllotoxin (Fig. 4), a non-alkaloid toxin lignan, is a laxative, anti-tumor and antirheumatic agent. Cell cultures of Linum flavum were shown to be able to convert deoxypodophyllotoxin, a lignan isolated from Anthriscus sylvestris, into podophyllotoxin. ... 

The chiral lactone (178) has been used for the synthesis of a variety of natural products, such as sugars, lignans, terpenes, alkaloids, and P-lactams as a chiral building block 182c,184). The use of (178) as a powerful inductor of asymmetry was mainly established by Takano et al. 181, 84> one can expect more highly interesting reports from this group. 

N.A. Galactoside-specific lectin, lignans, viscotoxin, choline, alkaloids, resin, acetylcholine, protein, flavonoids, caffeic acid, viscin, carotenoids.99100 181 Lower blood pressure, stimulate heart action, and treat arteriosclerosis. 

The fully aromatic A,B-diheteropentalenes do not occur in nature. However, the reduced furofurans and pyrrolopyrroles are present in a variety of natural products such as lignans, fungal metabolites and alkaloids. It is beyond the scope of this chapter to present an exhaustive survey of these compounds. However, a few selected examples are presented in formulae (376)-(380). 

Many species of phyllanthus have been used in Ayurvedic medicine for more than 2000 years. It is a traditional remedy for ailments such as jaundice, dysentery, diabetes, skin ulcers, and urinary tract infections. Phyllanthus s principal constituents — lignans, alkaloids, and bioflavonoids — have been found to act primarily on the liver, which confirms its traditional use in the treatment of jaundice. Phyllanthus amarus attracted the attention of Nobel prize winner Baruch Blumberg. He and others studied its uses in preventing hepatitis B and devised a vaccine. 

The American tree T. brevifolia is famous for its well-known taxane diter-pene alkaloid taxol, and its derivatives have been isolated [5,7,9]. In fact, brevitaxin, the first known terpenolignan, was also isolated from the twigs of the Himalayan yew T. brevifolia [19]. Its was identified using spectral methods, particularly 1-D and 2-D NMR techniques such HMBC and SINEPT experiments, which were used to establish regiochemistry of the terpene-lignan linkage. 

There are abundant and diverse flavonoids with carbohydrates and lipids, alkaloids (betalain alkaloids and other alkaloids), phenols (chromones, cou-marins, lignans, quinines, and other phenolics), terpenoids (monoterpenoids, sesquiterpene lactones, triperpenoid saponins, carotenoids, and other terpenoids), and minerals as micronutritional phytochemicals in fruits and vegetables of our daily diets. Among these phytochemicals, the flavonoids have specific functionality in relation to age-related diseases such as hypertension, diabetes, cardiac infarction, cataracts, and cancer. The authors of each chapter in the first section have presented their evidence in relation to the mechanism of the preventative and therapeutic ability of the compounds. 

From Taxus baccata (Taxaceae) the alkaloid taxol has been isolated. Taxol also affects the architecture of microtubules in inhibiting their disassembly (312). Nonalkaloidal compounds to be mentioned in this context include the lignan podophyllotoxin (312). In conclusion, any alkaloid which impairs the function of microtubules is likely to be toxic, because of their importance for a cell, and, from the point of view of defense, a well-working and well-shaped molecule. 

More recent applications in target-oriented synthesis took advantage of the BVMO platform for the generation of enanhocomplementary lactones. In this context, butyrolactones represent appealing intermediates due to the facile availability of prochiral ketone substrates for enzyme-mediated desymmetrizations Scheme 21.7 indicates the potenhal in lignan total synthesis based on products obtained in a previous study [46]. The collechon of BVMOs exploited by our groups also allowed efficient access to various indole alkaloids via enanhocomplementary lactones obtained in the desymmetrizahon of fused bicycloketones [35]. 

Isoquinoline alkaloids Phenylpropanoids Flavonoids, stibenes, catechins Lignin, lignans Coumarins, furanocoumarins Cyanogenic glycosides Glucosinolates Quinones,... 

---