2-Amino-4-hydroxypteridines, pterin

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. 

Because of the prevalence of its derivatives, 2-amino-4-hydroxypteridine has been given the trivial name pterin. Its structure resembles closely that of guanine, the 5-membered ring of the latter having been expanded to a 6-membered ring. In fact, pterins are derived... 

Pterins belong to a family of nitrogen heterocyclic compounds and consist of 2-amino-4-hydroxypteridine. Due to keto-enol tautomerism (Eq. 1), pterin exists generally as the 4-keto, i.e. amido, form that is illustrated as 2-aminopteridin-4(3H)one (4) rather than the enol form (3). Various pterin derivatives have been unexceptionally isolated from almost all kinds of living organisms and almost all such pterin derivatives have carbon substituents on the C(6) position. 

See also molecularity order of reaction. pterin 2-Amino-4-hydroxypteridine. 

Pterin (2-amino-4-hydroxypteridine, which occurs in the lactam form 8) and lumazin (2,4-dihy-droxypteridine, which exists as the l,2,3,4-tetrahydropteridine-2,4-dione structure 9) are the basic structures of the naturally occurring pteridine derivatives ... 

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