Pteridines, quaternary salts

It is only recently that the first pteridine quaternary salt was prepared. Brown and Jacobson treated 4-dimethylaminopteridine (156) and its 6,7-dimethyl derivative with methyl iodide in boiling methanol and obtained the corresponding salts (cf, 157). The structure of these... 

Pteridines have been converted into nucleoside derivatives by attaching a sugar group to an annular nitrogen atom. The products are not quaternary salts.189 Compound 82 reacts with methyl tosylate at N-3 rather than at N-l because it is less hindered.190... 

The pyridinium ylide (24) is obtained from the reaction of 8-bromotheophylline with pyridine. Alkylsulphonate salts of caffeine have been synthesized. A new purine-into-pteridine ring transformation has been discovered. For example, the quaternary salt (25) was obtained by direct alkylation of an appropriate xanthine with ethyl bromoacetate. Base-catalysed hydrolysis of (25) gave the pyrimidine (26), which could be cyclized to give the isoxanthopterin derivative (27). 

Many jr-deficient azaarrmatic compounds (pyridines, pyrimidines, pyrazines, tri-azines, pteridines, and so on) and especially their quaternary salts have a tendency to add water to give the corresponding o -adducts [1,2,11,114—117,138]. A similar process of reversible pseudobase formation due to the addition of the hydroxide ion to A-aUcylazinium [11], 1,4-diazinium [114, 138], and 1,2,4-triazinium [115-117] cations has been well documented in the literature. For instance, 3-phenyl-5,6-dicyano-l-ethylpyrazinium tetrafluoroborate easily adds water under basic conditions to give the corresponding 2-hydroxy adduct (Scheme 37) [138]. 

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See also in sourсe #XX -- [ ]

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