- Synthesis and physicochemical characterization of (6: S)-5-formiminotetrahydrofolate; A reference standard for metabolomics
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The one-carbon carrier of the formate oxidation level derived from the interaction of tetrahydrofolate and formiminoglutamate, which has been tentatively identified as 5-formiminoltetrahydrofolate, has been prepared by chemical synthesis. Treatment of a solution of (6S)-tetrahydrofolate in aqueous base with excess ethyl formimidate in the presence of anti-oxidant under anaerobic conditions afforded a gummy solid which, based on mass spectral analysis, conformed to a monoformimino derivative of tetrahydrofolate. Further physicochemical characterization by validated methods strongly suggested that the product of chemical synthesis was identical to the enzymatically produced material and that it was, in fact, (6S)-5-formiminotetrahydrofolate. Conditions and handling methods toward maintaining the integrity of this highly sensitive compound were identified and are described, as is analytical methodology, useful for research studies using it.
- Lewin,Silinski,Zhong,Gilbert,Mascarella,Seltzman
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p. 5684 - 5690
(2018/08/17)
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- Enantioselective catalyses CXXXV [1]. Stereoselective hydrogenation of folic acid and 2-methylquinoxaline with optically active rhodium(I)-phosphane complexes
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In the hydrogenation of the C=N double bonds of the pyrazine ring of folic acid to 5,6,7,8-tetrahydrofolic acid a new asymmetric center is formed at C6 of the pteridine system. With rhodium(I) catalysts made from optically active phosphanes, which are immobilized on silical gel, the hydrogenation in aqueous solution can be controlled stereoselectively. The highest diastereomeric excess of ca. 40% is obtained with (-)-BPPM containing catalysts. The hydrogenation of the biomolecule folic acid in aqueous solution is also possible homogeneously with rhodium(I)-phosphane catalysts, the ligands of which contain sulfonic acid groups and polyether fragments. The homogeneous hydrogenations proceed slower and with somewhat reduced diastereoselectivities compared to the heterogeneous catalyses. The hydrogenation of 2-methylquinoxaline is a model system for the reduction of folic acid. The usual rhodium(I)-phosphane catalysts afford only small enantioselectivities.
- Brunner, Henri,Rosenboem, Sabine
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p. 1371 - 1382
(2007/10/03)
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- Synthesis of Tetrahydropteridine C6-Stereoisomers, Including N5-Formyl-(6S)-tetrahydrofolic Acid
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Chiral N1-protected vicinal diamines derived from amino acids were condensed with 2-amino-6-chloro-5-nitro-4(3H)-pyrimidinone, the nitro group reduced, and the amine deprotected.Oxidative cyclization of the resulting triaminopyrimidinone via quinoid pyrimidine intermediates gave a quinoid dihydropteridine, which was then reduced to a tetrahydropteridine C6-stereoisomer.Thus, 6(R)- and 6(S)-propyltetrahydropterin were stereospecifically synthesized (99 percent enantiomeric purity) in good yield from D- and L-norvaline, respectively.Reductive alkylation of (p-aminobenzoyl)-L-glutamate with a niropyrimidine aldehyde derived from D- or L-serine similarly afforded, after cyclization and reduction, (6R)- or (6S)-tetrahydrofolic acid.The latter was then converted to the natural isomer of leucovorin by regioselective N5-formylation with carbonyl diimidazole / formic acid without loss of enantiomeric purity.
- Bailey, Steven W.,Chandrasekaran, Rama Y.,Ayling, June E.
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p. 4470 - 4477
(2007/10/02)
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- Stereochemistry of Reduction of the Vitamin Folic acid by Dihydrofolate Reductase
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Reduction of the vitamin folic acid (6) to the coenzyme 5,6,7,8-tetrahydrofolic acid (1) by the enzyme dihydrofolate reductase is shown to involve transfer of the 4-pro R hydrogen of NADPH to the same face at both C-6 and C-7 of the pteridine system (the re face at C-6 and the si face at C-7).The orientations of the pteridine system of folic acid (6) and of dihydrofolic acid (5) when bound to the enzyme are different from the orientation of the pteridine ring of the anti-cancer drug methotrexate (11) when bound to this enzyme.
- Charlton, Peter A.,Young, Douglas W.,Birdsall, Berry,Feeney, James,Roberts, Gordon C. K.
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p. 1349 - 1354
(2007/10/02)
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