Über Pterinchemie. 69 Mitteilung [1]. Konformationsanalyse von 5,6,7,8‐Tetrahydropteroinsäure und 5,6,7,8‐Tetrahydro‐<scp>L</scp>‐folsäure

Furrer, H; Bieri, Jost H.; Viscontini, M.

doi:10.1002/hlca.19780610743

Cited by 24 publications

(6 citation statements)

References 16 publications

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“…The chemical shifts and spin-spin coupling constants observed in the spectrum replotted for Figure 2 for the major species of 5-CHO-H4folate are given in Table I. The assignments given in Table I are the same as those of tetrahydrofolate for the C(2/,6')-2H, C(3',5')-2H, -CH, t-CH2, /3-CHa, and /3-CHB resonances (Poe & Hoogsteen, 1978;Furrer et al, 1978).…”

Section: Resultsmentioning

confidence: 99%

5-Formyl- and 10-formyl-5,6,7,8-tetrahydrofolate. Conformation of the tetrahydropyrazine ring and formyl group in solution

Poe¹,

Benkovic²

1980

Biochemistry

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The chemical shifts and spin-spin coupling constants for the 300-MHz 1H NMR spectra of (6RS)-10-formyl-and (6RS)-5-formyl-5,6,7,8-tetrahydro-L-folate at 25 degrees C in 0.1 M NaOD and at neutral pH are reported and analyzed. Assignments of most resonances are based on comparison to closely related compounds; the resonances of C(6)-H, C-(7)-2H, and C(9)-2H are assigned by preparation of specifically deuterated formyltetrahydrofolates. From analysis of the C(7)-2H spin-spin coupling constants, it is proposed that the tetrahydropyrazine rings of both 10-formyl- and 5-formyl-H4folate are in a half-chair conformation with C(6)-H equatorial. It is further proposed from model building that the 5-formyl group and C(9) of 5-formyl-H4folate are trans. In the 1H NMR spectrum of 5-CHO-H4folate, there was a minor species which was present at a concentration roughly one-sixth that of the major species; this species did not correspond to oxidized 5-CHO-H4folate and could not be separated from the major species by gel permeation or ion-exchange chromatography. It is proposed that this minor species corresponds to a conformer of 5-CHO-H4folate in slow exchange with the major conformer; this slow exchange is attributed to slow rotation due to a partial double bond character of the N(5) to 5-formyl-carbon bond. During the preparation of 10-formyl-H4folate from 5,10-methenyl-H4folate in D2O, approximately 60% of the formyl hydrogen was exchanged for deuterium. The equilibrium constant for the interconversion of 5,10-methenyl-H4folate and 10-formyl-H4folate, K' = [5,10-methenyl-H4folate]/([D+][10-formyl-H4folate]), was measured to be (1.4 +/- 0.6) X 10(6) M-1 in D2O at 25 degrees C.

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Section: Resultsmentioning

confidence: 99%

5-Formyl- and 10-formyl-5,6,7,8-tetrahydrofolate. Conformation of the tetrahydropyrazine ring and formyl group in solution

Poe¹,

Benkovic²

1980

Biochemistry

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“…NMR studies of CH2-H4folate by have shown that the resonances of the p-aminobenzoyl-L-glutamate moiety of CH2-H4folate exhibit about the same chemical shifts as corresponding protons of tetrahydrofolate (Poe & Hoogsteen, 1978;Furrer et al, 1978). Importantly, T atum et al (1977) demonstrated that the protons of the methylene bridge Cn were nonequivalent with a chemical shift difference of 1.21 ppm and geminal spin-spin coupling of 4 Hz.…”

Section: Results and Discussion Previousmentioning

confidence: 99%

5,10-Methylene-5,6,7,8-tetrahydrofolate. Conformation of the tetrahydropyrazine and imidazolidine rings

Poe¹,

Jackman²,

Benkovic³

1979

Biochemistry

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“…A 13C NMR investigation (Armarego & Waring, 1980) and several 'H NMR studies (Storm & Chung, 1976;Weber & Viscontini, 1977; Armarego & Schou, 1977;Ganguly et al, 1981) of H4pterins and the closely related tetrahydrofolates (Poe & Benkovic, 1980;Poe et al, 1979a,b;Poe & Hoogsteen, 1978;Furrer et al, 1978) have concluded that the tetrahydropyrazine ring assumes one of two essentially equivalent cyclohexene-like half-chair conformations which differ only in the preferred orientations of their C6 and C7 substituents. Abbreviations: NMR, nuclear magnetic resonance; H4biopterin, 5,6,7,2-H4pterin, rranv-6,7-dimethyltetrahydropterin; cis-6,7-(CH3)2-H4pterin, m-6,7-dimethyltetrahydropterin; PAH, phenylalanine hydroxylase; TSP, 2,2,3,3tetradeuterio-3-(trimethyisilyl)propionate (sodium salt); D20, deuterium oxide; NADH, nicotinamide adenine dinucleotide (reduced form); d, deuterium (as used in naming the specifically deuterated analogues); DDQ, dichlorodicyanobenzoquinone; pH*, pH uncorrected for the deuterium isotope effect; FID, free induction decay; TCA, trichloroacetic acid; Hz, hertz; NOE, nuclear Overhauser effect.…”

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confidence: 99%

Tetrahydrobiopterin analogs: the solution conformations of 6-methyltetrahydropterin, 7-methyltetrahydropterin, and cis- and trans-6,7-dimethyltetrahydropterins as determined by proton nuclear magnetic resonance

Williams¹,

Storm²

1985

Biochemistry

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The conformation of tetrahydrobiopterin analogues in aqueous solution at 23 degrees C has been determined by analyzing the 200-MHz 1H NMR spectral parameters of the enzymatically active 6-methyltetrahydropterin, 7-methyltetrahydropterin, and cis- and trans-6,7-dimethyl-5,6,7,8-tetrahydropterins. Each of these cofactors, with the exception of the cis-6,7-dimethyl isomer, exhibited an unusually small trans 6H-7H spin-spin coupling (8.5-9.1 Hz). An empirical equation that accounts for the effects of substituent electronegativity and orientation on vicinal couplings [Haasnoot, C. A. G., deLeeuw, F. A. A. M., & Altona, C. (1980) Tetrahedron 36, 2783-2792] predicted this coupling to be 11.3-11.6 Hz. We attribute the discrepancy between the calculated and experimentally observed values of this coupling to hyperconjugation of the axially oriented C7-H bond with the pi orbital of the vinylogous amide protein of the pterin ring (N8-C8a = C4a-C4 = O) rather than conformational averaging. The trans 6H-7H interproton distance in the 6-methyl analogue is calculated to be 3.0 A from the measured decrease in the spin-lattice relaxation rate of the axially oriented C7 proton after specific deuteration at C6. This is consistent with the single-conformer interpretation. Chemical shift comparisons of the methyl resonances of these analogues, NOE measurements from selectively deuterated analogues, and the differential sensitivities of axially vs. equatorially disposed ring protons to protonation at N5 all indicate that (i) the methyl substituents at both the C6 and C7 positions markedly prefer equatorial-like orientations and (ii) the tetrahydropterin ring is, with the exception of a pronounced pucker at C6, nearly planar.(ABSTRACT TRUNCATED AT 250 WORDS)

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Über Pterinchemie. 69 Mitteilung [1]. Konformationsanalyse von 5,6,7,8‐Tetrahydropteroinsäure und 5,6,7,8‐Tetrahydro‐L‐folsäure

Cited by 24 publications

References 16 publications

5-Formyl- and 10-formyl-5,6,7,8-tetrahydrofolate. Conformation of the tetrahydropyrazine ring and formyl group in solution

5-Formyl- and 10-formyl-5,6,7,8-tetrahydrofolate. Conformation of the tetrahydropyrazine ring and formyl group in solution

5,10-Methylene-5,6,7,8-tetrahydrofolate. Conformation of the tetrahydropyrazine and imidazolidine rings

Tetrahydrobiopterin analogs: the solution conformations of 6-methyltetrahydropterin, 7-methyltetrahydropterin, and cis- and trans-6,7-dimethyltetrahydropterins as determined by proton nuclear magnetic resonance

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