Some Nitrogen-Containing Natural Products

Besides the large group of alkaloids some nitrogen-containing natural products, do not fall under the definition of alkaloids, and are therefor discussed separately. 

Alkaloids are a group of nitrogen-containing natural products that occur primarily in higher plants, although they are also found in some fungi, such as mushrooms. The name alkaloid (meaning alkali-like ) is applied because they are amines and thus basic. Their basic character allows them to be readily isolated from their plant source. The plant material is extracted with aqueous acid. This converts the alkaloid to an ammonium cation, which is water soluble. Neutralization of the acidic extract with base causes the alkaloid to precipitate. 

In today s world, some plant-derived secraidary metabolites play a great role in pharmaceutical production, among them nitrogen-containing natural compounds called alkaloids. Some alkaloids are produced by synthesis or enzymatic methods and others are obtained from plants. Unfortunately, overexploitation of these plants has made them endangered species. Therefore, appropriate technologies for sustainable use and sufficient focus on the biosynthetic routes and methods of isolation of these secondary metabolites derived from the plants are required. 

The carbon-carbon unsaturated substrates have now expanded from aminoalkenes to aminoalkynes, aminoallenes, and aminodienes, and the hydroamination/cyclization reactions of these substrates have produced functionalized nitrogen-containing heterocycles. It is worth noting that the aminoallene hydroamination/cyclization reactions are highly diastereoselective, and can provide concise routes to the synthesis of some natural products (Figure 8.38) [126]. 

Heterocyclic amines contain nitrogen as a part of the ring, bound to two carbon atoms. Many of these amines are found in coal tar and a variety of natural products. Some aromatic and heterocyclic amines are called by their common names. 

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