Pteridin-4 -ones 4,5-diamino

No simple pteridine 1- or 3-oxides are yet known. If the AT-atom of an amide function is formally oxidized, tautomerism favours the cyclic hydroxamic acid structure, as found for 3-hydroxypteridin-4-one (55JA3927), 1-hydroxylumazine (64JOC408) and 2,4-diamino-8-hydroxypteridin-7-ones (75JOC2332). 

Of the classical Hofmann, Curtius, Lossen and Schmidt degradations, only a rare example of the first is known, hypobromite converting 4,7-diamino-2-phenyl-6-pteridinecar-boxamide (208) into 8-amino-2,3-dihydro-6-phenyl-l//-imidazo[4,5-g]pteridin-2-one (209 equation 64) (63JOC1203). 

Pteridin-7-one, 4-alkoxy-2-amino-sulfurization, 3, 297 Pteridin-7-one, 4-alkoxy-2,4-diamino-sulfurization, 3, 297 Pteridin-7-one, 8-alkyl-3,4-dihydro-UV spectrum, 3, 279... 

Pteridin-7-one, 2,4-diamino-8-hydroxy-structure, 3, 282 Pteridin-7-one, 5,6-dihydro-oxidation, 3, 307 structure, 3, 279 Pteridin-7-one, 8-hydroxy-synthesis, 3, 319 Pteridin-7-one, 8-methyl-synthesis, 3, 297... 

Diamino-, 4-amino-2-methylthio-, and 2-amino-4-alkoxy-pteridines react similarly <86MI 718-05, 88HCA531). Deoxysepiapterin (120), one of the two yellow Drosophila eye-pigments, could be... 

An interesting pyrazine ring formation was detected between 5,6-diamino-1,3-dimethyluracil (309) and 6-hydroxy-6-(2,3,5-tri-0-benzoyl-/ -D-ribofuranosyl)-2//-pyran-3(6//)-one (310) leading to a mixture of l,3-dimethyl-7-(2,3,5-tri-0-benzoyl-/ -D-ribofuranosyl)lumazine (311), 1,3-dimethyl-6-[3-(2,3,5-tri-0-benzoyl-/ -D-ribofuranosyl)-3-oxopropyl]-lumazine (312), and 6,8-dimethyl-l-(2,3,5-tri-0-behzoyl-/ -D-ribofuranosyl)pyrrolo[l,2-/]pteridine-7,9-dione (313) (Equation (14)) <89JOC3927>. 

The synthesis of the pteridine ring system has been approached by two obvious routes one is the fusion of the pyrazine ring onto a pre-formed 4,5-diamino-pyrimidine, and the second, the elaboration of the pyrimidine ring on a pre-formed pyrazine. The first of these, the Isay synthesis, suffers from the disadvantage that condensation of the heterocyclic 1,2-diamine with an unsymmetrical 1,2-dicarbonyl compound... 

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