Pteridines, structure

Thiazino[2,3-6]pteridine structure, 3, 284 Thiaziridines dioxides synthesis, 7, 197 Thiaziridinimines existence, 7, 197 Thiazirines synthesis, 7, 196 Thiazirines, 3-phenyl-synthesis, S, 45 Thiazole, 2-acetoxy-4-methyl-synthesis, 6, 254... 

Thiazolo[2,3-6]oxazolium salts, 2,3-dihydro-synthesis, 6, 992 Thiazolo[2,3-6]pteridines structure, 3, 284 Thiazolo[3,2-a]pteridines structure, 3, 284 Thiazolopurines, 5, 566... 

Thieno[3,4-d]oxazole-3a(4H)-carboxylic acid, dihydro-2-methyl-synthesis, 6, 1020 Thieno[2,3-d Joxazoles synthesis, 6, 990 Thieno[3,2-g]pteridine structure, 3, 284 lH-Thieno[3,4-c]pyran-2-ones synthesis, 4, 1032 Thienopyrazines synthesis, 4, 1022-1024 Thieno[2,3-6]pyrazines, 4, 1023 electrophilic substitution, 4, 1024 Thieno[3,4-6]pyrazines, 4, 1024 Thieno[3,4-c]pyrazole, 4,6-dihydro-3-hydroxy-carbamates... 

Pyrimido[l,2-a][l,8]naphthyridines synthesis, 2, 599 Pyrimido[5,4-c]oxadiazine purine synthesis from, 5, 591 Pyrimido[4,5-6][ l,4]oxazine synthesis, 3, 312 Pyrimido[2,1 -6]pteridine structure, 3, 284 Pyrimido[5,4-g]pteridine structure, 3, 284 Pyrimidopurines, 5, 566 Pyrimido[4,5-c]pyridazine, aryl- H NMR, 3, 335... 

Thiazino[2,3-6]pteridine structure, 3, 284 Thiaziridines dioxides synthesis, 7, 197 Thiaziridinimines existence, 7, 197 Thiazirines... 

The flavin or isoalloxazine moiety is a polycyclic structure comprised of a benzene, a pyrazine, and a pyrimidine ring. It is of interest to note that the latter two rings are found in the pteridin portion of folic acid and that this pteridin structure was first found in certain pigments isolated from butterfly wings. 

These differences when viewed isolated from other facts seem to suggest that the natural cofactor is not a pteridine. An alternate view is that they (especially items 3, 4, and 5) point to a lowered reactivity of the cofactor as compared to the synthetic tetrahydropteridines which have been used. Such a lowered reactivity could be the result of a substitution on the pteridine ring. Until more is known about the structure of the cofactor, the significance of these differences cannot be fully evaluated. They do not, however, necessarily constitute evidence against a pteridine structure for the cofactor. 

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