Purines Biologically important heterocyclic

Many biologically important heterocyclic compounds have fused (condensed) ring systems. In particular, the purines adenine and guanine are found in DNA (with cytosine, 5-methylcytosine, and thymine) and also in RNA (with cytosine and uracil). 

Section 28 1 Many biologically important compounds are related to the heterocyclic aromatic compounds pyrimidine and purine... 

This chapter discusses the transition metal catalyzed functionalization of such systems that fall outside the topic of Chapters 6 and 7, as well as certain other compound classes (e.g. purines, pyrones). In contrast to the abundant literature of the chemistry of five and six membered systems, the transition metal catalyzed transformations of other heterocycles have not been studied so far in the same depth, probably due to the limited availability of their halogen derivatives compared to haloazines and haloazoles. Purine compounds and their structural analogues constitute an exception, since their biological importance proved to be a strong drive for synthetic chemist worldwide.1... 

The fifth chapter, Tetrahydrobiopterin and Related Biologically Important Pterins by Shizuaki Murata, Hiroshi Ichinose and Fumi Urano, describes a modern aspect of pteridine chemistry and biochemistry. Pteridine derivatives play a very important role in the biosynthesis of amino acids, nucleic acids, neurotransmitters and nitrogenmonooxides, and metabolism of purine and aromatic amino acids. Some pteridines are used in chemotherapy and for the diagnosis of various diseases. From these points of view, this article will attract considerable attention from medicinal and pharmaceutical chemists, and also heterocyclic chemists and biochemists. 

The purines are another biologically important class of fused-ring heterocycles. They contain a pyrimidine ring fused to an imidazole ring. 

More than 50% of all known organic compounds are heterocyclic compounds. They play important roles in medicine and biological systems. A great majority of important drugs and natural products, e.g. caffeine, nicotine, morphine, penicillins and cephalosporins, are heterocyclic compounds. The purine and pyrimidine bases, two nitrogenous heterocyclic compounds, are structural units of RNA and DNA. Serotonin, a neurotransmitter found in our body, is responsible for various bodily functions. 

The biological activity of azoles and their derivatives (indoles, purines, etc.) and their abundance as structural motif in natural products made them a prime target and test ground in the development of catalytic transformations. This chapter is mainly dedicated to the reactions of monocyclic five membered heterocycles and indole. The chemistry of other condensed systems of importance, such as purines, is discussed in Chapter 8. 

Two derivatives of nicotinamide (pyridine-3-carboxylic amide), one of the B2 vitamins, nicotinamide adenine dinucleotide (NAD ) and nicotinamide adenine dinucleotide phosphate (NADP ), serve as redox coenzymes. Of the three heterocyclic ring systems found in these coenzymes, i.e. those of purine, ribose and pyridine, it is the pyridine portion that is reactive in redox reactions. Biologically, two oxidation states are important the oxidized form, NAD(P)+, and the 1,4-dihydro isomer of the two-electron reduced form, NAD(P)H (Scheme 1). Nicotinamide coenzymes interconvert between these two oxidation states in... 

Glycosides are compounds in which the substituent is bound to the anomeric carbon. This group comprises numerous natural products the primary metabolites. The most important are nucleosides, the basic structural units from which nucleotides and nucleic acids are formed. The monosaccharide component of the nucleoside is D-ribose or its partially reduced form D-deoxyribose. In biochemistry and molecular biology the most important are the nucleosides in which ribose is bonded to heterocyclic molecules called nucleic bases. The most common nucleic bases are pyrimidines and purines. 

Monocyclic and Bicyclic aromatic heterocycles such as imidazoles, thiazoles, thiadiazoles, oxazoles, oxadiazoles quinazolines, indoles, benzimidazoles, purines pyrido[43-d]pyri-midines, thiazolo[5,4-d]pyrimidines, thiazolo[4,5-d]pyrimidines, oxazolo[5,4-d]pyrimi-dines and thieno[2,3-d]pyrimidines are renowned pharmacophores in drug discovery. These special structures are well explained and exemplified in chemical compound libraries. In this chapter, several types of thiazole based heterocyclic scaffolds such as mono-cyclic or bicyclic systems synthesis and their biological activities studies are presented, which are not frequently present in books and reviews. We mention the first importance of synthetic route of various thiazole based compounds and their applications in medicinal chemistry in this chapter. 

Nature abounds with compounds having a heterocyclic aromatic ring fused to one or more other rings. Two such compounds especially important in the biological world are indole and purine ... 

The preparation of functionalized uracils and purines is of high interest due to the biological properties of these important classes of heterocycles [97]. Starting from various protected 5-iodouracils such as 168, the addition of iPrMgBr (—40 C, 45 min) leads to the formation of the corresponding magnesium compound 169 that can be trapped by various aldehydes, ketones and acid chlorides, leading for instance, after transmetallation to copper and reaction with benzoyl chloride to ketone 170 in 73% yield (Scheme 4.35) [98]. 

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