Benzo pteridines

Benzo[g]pteridine, 2,4-diaminotetrahydro-synthesis, 3, 317 Benzopurines, 5, 567 Benzopyranones... 

Just as 2- or 4-substituted pteridines are usually degraded to pyrazines, similarly substituted benzo[g]pteridines have also been observed to afford quinox-alines under vigorous hydrolytic or aminolytic conditions. The following examples illustrate some such degradations. 

Figure 16-8. Structure and labeling of the isoalloxazine ring and related flavins. Isoalloxazine (benzo[g]pteridine-2,4(3H,10H)-dione) R = R = H. FMN (Flavin mononucleotide) R = CH3 R = CH2- (CH0H)3-CH20-P0f-...

Pyrimidines fused to other six-membered rings, most frequently in the form of bicyclic structures, can be degraded to corresponding substituted monocyclic pyrimidines. Fused pyrimidine structures described are benzo- (quinazolines), pyrano[2,3-tf]-, pyrazino[2,3-i/j- (pteridines), pyrimido[l,2-u]-, pyrimido[4,5-i/]pyrimidines, and pyrimido[5,4-e]-a -triazines, pyrimido[5,4- f]-v-triazine, pyrim-ido[4,5-i/][l,3]oxazines, pyrimido[5,4-i/][l,3]oxazine, pyrimido[4,5- ][l,4]thiazines, pyrimido[5,4- ][l,4]thiazines, and pyrimido[4,5-e][l,2,4]thiadiazines. References to these reactions can be found in . 

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