Pterins natural

Das erste dieser Pterine, ein gelbes Pigment, wurde von Forrest und Mitchell (14, 15) isoliert und naher untersucht. Den Beweis seiner Pterin-natur brachte die photochemische Zersetzung bei Bestrahlung mit Sonnenlicht in alkalischer Losung, wobei die Pterin-6-carbonsaure (XII)... 

All compounds of this heterocyclic ring system so far found in nature are derivatives of pterin (2) and lumazine (3) carrying different substituents in the 6- and/or 7-positions. The most common representatives of these series are listed in Tables 8 and 9. 

Pterins — These are pigments derived from pteridine skeletons. All natural pterins are 2-amino-4-hydroxypteridines bearing various substituents at Cg and C7 and having different oxidation states of N5 and Ng. 

The importance of the dihydro and tetrahydro oxidation states of pterins in biology has stimulated interest in the study of the chemical properties of these compounds, especially with respect to electron-transfer and radical reactions. It has become apparent, perhaps unsurprisingly, that the stability and reactivity of these oxidation states are very sensitive to substituent effects and the much greater stability of the fully conjugated pteridines is most evident. The oxidation of tetrahydropterins and the reduction of dihydropterins have become especially important in the chemistry of nitric oxide production in nature and in oxidative stress but the accumulation of relevant facts has not led so far to a detailed understanding of the chemical property relationships. Relevant information is summarized in the following section. 

The obvious similarity between the purine bases of DNA and pteridines, especially between guanosine and pterins, has encouraged extensive studies of the synthesis and properties of pteridine-containing nucleoside and nucleotides. Synthetic methods have naturally built upon established methods of nucleic acid synthesis. The primary property of use in applications of these compounds to DNA chemistry is fluorescence, which is very much greater for pteridines than for purines. 

The natural cofactor of the AAHs, BH4 (Scheme 2), is a heterocyclic compound chemically classified as a pteridine that includes a fused pyrimidine and pyrazine rings. As many other naturally occurring pteridines BH4 has a pterin structure, which includes an amino substituent in position 2 and an oxo group in position 4 of the pyrimidine ring. The term biopterin is reserved for pterins with a dihydroxypropyl group in position 6. 

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