Pteridin-4 -ones

The action of sulfur nucleophiles like sodium bisulfite and thiophenols causes even pteridines that are unreactive towards water or alcohols to undergo covalent addition reactions. Thus, pteridin-7-one smoothly adds the named S-nucleophiles in a 1 1 ratio to C-6 (65JCS6930). Similarly, pteridin-4-one (73) yields adducts (74) in a 2 1 ratio at C-6 and C-7 exclusively (equation 14), as do 4-aminopteridine and lumazine with sodium bisulfite. Xanthopterin forms a 7,8-adduct and 7,8-dihydropterin can easily be converted to sodium 5,6,7,8-tetrahydropterin-6-sulfonate (66JCS(C)285), which leads to pterin-6-sulfonic acid on oxidation (59HCA1854). 

Aminopteridine is the most sensitive to acid hydrolysis, and 6-amino- and 6-dimethyl-amino-pteridine are also hydrolyzed, even by cold 0.0IN hydrochloric acid, too rapidly for accurate determination of the cation form (52JCS1620). 2-Amino- and 4-amino-pteridine are not readily attacked by IN HCl at 20 °C but at 100 °C the former compound is destroyed and the latter converted into pteridin-4-one (5UCS474). 2,4-Diaminopteridine can be hydrolyzed by refluxing in 6N HCl for 30 minutes to 2-aminopteridin-4-one (pterin 2) and after... 

There is also the possibility of removing the 2-oxo group by ring cleavage and subsequent recyclization. Lumazine can be hydrolyzed by strong alkali to 2-aminopyrazine-3-carboxylic acid (153) which is converted first into the amide (154) and then cyclized by ethyl orthoformate into pteridine-4-one (155 equation 47) (51JCS474). 

Pteridin-4-one, 3-amino-synthesis, 3, 318 Pteridin-4-one, 6-chloro-reactions, 3, 292... 

Pteridin-4-one, 7-chloro-2-methylthio-synthesis, 3, 296 Pteridin-4-one, 5,6-dihydro-structure, 3, 279 Pteridin-4-one, 7,8-dihydro-structure, 3, 279 Pteridin-4-one, 3-hydroxy-structure, 3, 282 synthesis, 3, 318... 

Pteridin-4-one, 7-(p-substituted phenyl)-hydroxylation, 3, 287 Pteridin-6-one, 7-amino-synthesis, 3, 314... 

Michael addition reactions, 3, 288 structure, 3, 271 Pteridin-4-ones... 

Ultraviolet spectral comparisons also indicate that structure 174 represents the predominant form of pteridin-4-one (a similar conclusion was reached for 2-amino-6,7-dimethylpteridin-4-one ), and a value of 1.72 has been calculated for log K p between forms 174 and 175 from pKa data. " It is possible, however, that the hydroxy... 

Brown and Jacobsen demonstrated by ultraviolet spectral comparisons that 2-amino-(3H)-pteridin-4-one was the predominant tautomeric form. The evidence in favor of 4-amino-(lH)-pteridin-2-one is less conclusive, but, nevertheless, convincing. 

Arylpyrazino[2,3-rf][l,3]oxazin-4-ones are precursors for several pteridinones such as 2-aryl-(3//)-pteridin-4-ones and 2-arylpteridin-4-ones <78JAP(K)53002499>. This is a new synthetic approach for these interesting bicycles and proceeds in good yield. 

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