Pterins synthesis, structure

Pterin, 4-amino — see Folic acid, 4-amino-4-deoxy-Pterin, 6-amino-structure, 3, 276 Pterin, 7-amino-structure, 3, 276 Pterin, 6-arylthio-reactivity, 3, 299 Pterin, 6-(l-carboxyethoxy)-synthesis, 3, 309 Pterin, 6-carboxy-7-hydroxy-properties, 3, 277 Pterin, 7-carboxy-6-hydroxy-properties, 3, 277 Pterin, 6-chloro-nucleophilic substitution, 3, 292 synthesis, 3, 290... 

Pterin, 5-formyl-6,7-dimethyl-5,6,7,8-tetrahydro-structure, 3, 281 Pterin, 6-hydroxymethyl-reactions, 3, 304 structure, 3, 273 Pterin, 7-hydroxymethyl-synthesis, 3, 311... 

Pterin, 8-methyl-synthesis, 3, 305 Pterin, 6-methyl-7,8-dihydro-hydrochloride structure, 3, 279... 

Aromatic compounds arise in several ways. The major mute utilized by autotrophic organisms for synthesis of the aromatic amino acids, quinones, and tocopherols is the shikimate pathway. As outlined here, it starts with the glycolysis intermediate phosphoenolpyruvate (PEP) and erythrose 4-phosphate, a metabolite from the pentose phosphate pathway. Phenylalanine, tyrosine, and tryptophan are not only used for protein synthesis but are converted into a broad range of hormones, chromophores, alkaloids, and structural materials. In plants phenylalanine is deaminated to cinnamate which yields hundreds of secondary products. In another pathway ribose 5-phosphate is converted to pyrimidine and purine nucleotides and also to flavins, folates, molybdopterin, and many other pterin derivatives. 

The evidence for a pterin-substituted 1,2-enedithiolate was first reported by Raja-gopalan, Johnson, and coworkers, who isolated pterins from the oxidative decomposition of molybdenum-bound MPT, Figure 4 [7,49,55,56], In complementary work, Taylor and coworkers confirmed the structure of several of the pterin decomposition products by direct synthesis (see Section V. A) [30,57-59], Urothi-one, first isolated in 1940 from human urine [60], was shown to be a metabolic degradation product of MPT [37], Other isolated pterin-containing decomposition and/or derivatized products from molybdenum enzymes include Form A, Form B (a urothione-like product), and camMPT (Figure 4) [7], Two other pterins, Form Z and the MPT precursor, can be obtained from molybdenum deprived organisms, N. crassa Nit-1, and oxidase-deficient children, neither of which pro-... 

The Taylor route is also very useful in the synthesis of more complex structures as demonstrated in the total synthesis of deoxyurothione (381), ( )-urothion (382) <89JA285>, and analogous 6,7-dihydrothieno[3,2- ]pterins (384) which are model substances of the oxidative breakdown product (383), termed form B of the molybdenum cofactor (399) <88JOC5839>. 

For a long time before the ring structure of pterins was known, compounds containing the pteridine ring were being prepared. In 1895, 2,4-dihydroxy-pteridine was prepared by oxidation of tolualloxazine and decarboxylation of the resulting 2,4-dihydroxypteridine-6,7-dicarboxylic acid, and the same compound was prepared in 1907 by the action of hypobromite on pyrazine-2,3-dicarboxamide. The condensation of 4,5-diaminopyrimidine and benziF to form 6,7-diphenylpteridine reported in 1906 was the first example of the most versatile general method of pteridine synthesis. 

Another wing pterin was found to be an isomer of xanthopterin and given the name isoxanthopterini. The synthesis of this colorless pterin was accomplished by condensation of ethyl mesoxalate with 2,4,5-triamino-6-hy-droxypyrimidine followed by decarboxylation of the intermediate as indicated in the above equations . A small amount of xanthopterin-7-carboxylic acid was also formed in the initial step, but in the presence of sulfuric acid, the products consist of 42% xanthopterin-7-carboxylic acid and 29% iso-xanthopterin-6-carboxyhc acid. Xanthopterincarboxylic add could not be decarboxylated but conversion to a dihydro derivative, decarboxylation of the dihydro derivative, and catalytic oxidation gave xanthopterin. Leuco-pterin can be reduced to a dihydroxanthopterin and reoxidized to xanthopterin. On the basis of absorption spectra of related derivatives, leucopterin and isoxanthopterin appear to have structures in which all of the hydroxyl groups indicated are in the lactam configuration . 

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