2-Amino- pteridin-4,7-dione

Xanthopterin monohydrate (2-amino-4,6-dihydroxypteridine, 2-amino-pteridin-4,6(lff,5ff)-dione) [5979-01-1 (H2O), 119-48-8 (anhydr)] M 197.2, m <300", pK, 1.6 (basic), pKj 6.59 (acidic), PK3 9.31 (acidic)(anhydrous species), and pKj 1.6 (basic), pK2 8.65 (acidic), PK3 9.99 (acidic)(7,8-hydrated species). Purification as for isoxanthopterin. Crystd by acidifying an ammoniacal soln, and collecting by centrifugation followed by washing with EtOH, ether and drying at 100° in vacuo. Paper chromatography Rp 0.15 ( -PrOH, 1% aq NH3, 2 1), 0.36 ( -BuOH,AcOH, H2O, 4 1 1) and 0.47 (3% aq NH3). [Inoue and Perrin J Chem Soc 260 7962 Inoue Tetrahedron 20 243 I964 see also Blakley Biochemistry of Folic Acid and Related Pteridines North Holland Publ Co, Amsterdam 1969.]... 

Another approach uses the reaction of 6-chloro-5-nitropyrimidines with a-phenyl-substituted amidines followed by base-catalyzed cyclization to pteridine 5-oxides, which can be reduced further by sodium dithionite to the heteroaromatic analogues (equation 97) (79JOC1700). Acylation of 6-amino-5-nitropyrimidines with cyanoacetyl chloride yields 6-(2-cyanoacetamino)-5-nitropyrimidines (276), which can be cyclized by base to 5-hydroxypteridine-6,7-diones (27S) or 6-cyano-7-oxo-7,8-dihydropteridine 5-oxides (277), precursors of pteridine-6,7-diones (278 equation 98) (75CC819). 

Pteridine-2,7-dione, 4-amino-8-benzyl-6-methyl-hydrolysis, 3, 294... 

Pteridine-4,7-dione, 8-methyl-2-methylthio-oxidation, 3, 299 Pteridine-4,7-dione, 2-methylthio-reactions, 3, 296 Pteridine-6,7-dione, 2-amino-synthesis, 3, 293... 

Pteridine-6,7-dione, 4-amino-2-chloro-chlorination, 3, 296 Pteridine-6,7-dione, 2,4-dichloro-synthesis, 3, 291 Pteridine-6,7-dione, 5-hydroxy-synthesis, 3, 316 Pteridine-6,7-dione, 8-methyl-reduction, 3, 298 Pteridine-2,6-diones structure, 3, 272 Pteridine-4,6-diones structure, 3, 272 synthesis, 3, 310 Pteridine-6,7-diones reduction, 3, 298 synthesis, 3, 316... 

New derivatives of 4-amino and 2,4-diaminopteridines have been synthesized and their capability to inhibit neuronal nitric oxide synthase evaluated <99JMC4108>. The synthesis of folic acid multiply labeled with stable isotopes, for bioavailability studies in human nutrition, has been reported <99JCS(P1)1311>, Synthesis and antiviral evaluation of several 6-(methylenecarbomethoxy)pteridine-4,7-diones have been described <99JHC435>. Synthesis and biochemical evaluation of bis(6,7-dimethyl-8-D-ribityllumazines) as potential bisubstrate analog inhibitors of riboflavin synthase have been reported <99JOC4635>. Synthesis and cyclization of novel lumazine-enediyne chimeras have been reported <99H13>. 

Dihydro-6-(D-arahino-tetritol-l-yl)pteridine-2,4-dione 668 was unequivocally prepared by condensation of l-amino-l-deoxy-o-fructose (42) with 6-chloro-5-nitrouracil followed by concomitant reduction and cycliza-tion of 667 (62JCS44) (Scheme 172). 

Pteridines may also be constructed from pyrimidines which are 4-(substituted)amino-5-unsub-stituted, from pyrimidine-4,5-diones (e g., alloxane), and front 5-halo-4-oxo-, 5-halo-4-amino-, or from 4,5-dihalopyrimidines. 

---