Pteridine-2,4-dione, methylation

The molecular features of covalent hydration are also present in the dihydroxy series, i.e., in pteridine-2,6-dione (30) and in pteridine-4,6-dione. The latter compound is hydrated only at the C(7)—N(8) double bond, whereas (30) forms two hydrated species, 7-hydroxy-7,8-dihydro- (29) and 4-hydroxy-3,4-dihydro-pteridin-2,6-dione (31) (equation 8). Structure (29) is thermodynamically the more stable substance (31) is formed more rapidly in solution but disappears slowly with time (63JCS5151). Insertion of a 4-methyl group greatly reduces the extent of 3,4- in favour of 7,8-hydration by a blocking effect . 

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... 

Trihydroxypteridine exists predominantly in the dioxo-mono-hydroxy form 191(R = H), its ultraviolet spectrum closely resembling those of both the 1- and the 3-methyl derivatives and that of l,3-dimethyl-7-methoxypteridine-2,4-dione (191, R = Me). These spectra are quite different from those of 8-methyl- (192, R = H) and l,3,8-trimethyl-pteridine-2,4,7-trione (192, R = Me), which are similar to each other and to those of other 8-substituted pteridine-2,4,7-triones. However, the ultraviolet spectrum of 2,4,7-trihydroxypteri-dine does, indeed, show that a small proportion of the trioxo form is present at equilibrium. A somewhat larger proportion of the 6-methyl derivative exists in the trioxo form, although structure 193 predominates. The trioxo form (194) of 2,4,7 trihydroxy-l,3,6-trimethyl-pteridine is the most important tautomer, but the corresponding 6-carboxylic acid exists entirely in the monohydroxy-dioxo form 195. 

An acid-catalyzed substitution of a 6-oxo group on 2-aminopteridine-4,6-dione with hydrogen chloride in alcohols (65-100°, 3 hr, 80% yield) represents a convenient synthesis of the 6-alkoxy analogs. The reaction proceeds also with pteridine-2,4,6-trione and its 1-methyl and 1,3-dimethyl derivatives. While methoxylation of 2,4,7-trichloro-quinoline gives about equal amounts of 2- and 4-substitution, acid-catalyzed hydrolysis gives specific reaction at the 2-position only. ... 

Methyl 4-methyl-3-[(A -phenylcarbamoyl)imino]-3,4,5,6,7,8-hexahydro-2-quino-xalinecarboxylate (201) underwent cyclization to give lO-methyl-3-phenyl-6,7,8,9-tetrahydrobenzo[g]pteridme-2,4(3//, 10/7)-dione (202) (Et3N, MeOH, reflux, 20 min 80%) and subsequent catalytic aromatization to 10-methyl-3-phenylbenzo[g]pteridine-2,4(3//, 10//)-dione (203) (Pd/C, decahydronaphtha-lene, reflux, 1 h 85%) analogs likewise. ... 

The investigation of the New Caledonian lithistid sponge Corallistes fulvodesmus led to the isolation of two polynitrogen compounds, 1-methyl-pteridine-2,4-dione, previously known as a synthetic product... 

---