Aiding a Better Understanding of Molybdopterin: Syntheses, Structures, and pKa Value Determinations of Varied Pterin-Derived Organic Scaffolds Including Oxygen, Sulfur and Phosphorus Bearing Substituents

Chrysochos, Nicolas; Ahmadi, Mohsen; Trentin, Ivan; Lõkov, Märt; Tshepelevitsh, Sofja; Ullmann, G. Matthias; Leito, Ivo; Schulzke, Carola

doi:10.1016/j.molstruc.2020.129867

Cited by 4 publications

(5 citation statements)

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“…However, all attempts to achieve ring closure turned eventually out to be unsuccessful. The starting material, 7-chloropterin (compound 3) was synthesized as described in the literature [23,24]. The etherification reaction between 7-chlorpterin, 3, and propargyl alcohol in the presence of NaH was carried out at room temperature.…”

Section: Resultsmentioning

confidence: 99%

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Synthesis, Characterization and Chlorination of 4-(Pentyloxy)-7-(prop-2-yn-1-yloxy)pteridin-2-amine

Correia

Wilke

Schulzke

2023

Molbank

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A new alkyne functionalized pterin derivative was synthesized through a reaction of 7-chloropterin with propargyl alcohol in the presence of sodium hydride. The purity and chemical structure of the compound was validated by NMR (1H, 13C) spectroscopy, Mass (APCI source) spectrometry, elemental analysis, and X-ray crystallography. The title compound may be further functionalized by exploiting the yne moiety, for instance, using click chemistry. The novel pterin derivative, most notably, in contrast to typical pterin behavior, is now soluble or even well soluble in almost any solvent except water.

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Section: Resultsmentioning

confidence: 99%

“…The starting material 7-chloropterin was synthesized as described in the literature [23,24]. 1 H NMR (300 MHz) and 13 C NMR (100 MHz) spectra were recorded on a Bruker Avance II-300 spectrometer.…”

Section: Methodsmentioning

confidence: 99%

Synthesis, Characterization and Chlorination of 4-(Pentyloxy)-7-(prop-2-yn-1-yloxy)pteridin-2-amine

Correia

Wilke

Schulzke

2023

Molbank

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“…This observation was rationalized as being the result of resonance stabilization of quinoxalinium by conjugation with the metallo-1,2-enedithiolate, an explanation consistent with the observation that quinoxaline protonation causes co-planarity between the dithiolene and quinoxaline structures. The p K a in 1-H can also be compared with the p K a values obtained in acetonitrile for a family of pteridines substituted to resemble aspects of PDT . The objective in that study was to synthesize soluble PDT analogues to obtain the p K a values under non-aqueous conditions.…”

Section: Resultsmentioning

confidence: 99%

“…The pK a in 1-H can also be compared with the pK a values obtained in acetonitrile for a family of pteridines substituted to resemble aspects of PDT. 82 The objective in that study was to synthesize soluble PDT analogues to obtain the pK a values under non-aqueous conditions. These pteridine analogues in acetonitrile exhibit pK a values in the range of 11.09−11.82, and theoretical computations of various protonated structures indicate that protonation is slightly more favored at N1 than at N5 or N8.…”

Section: ■ Introductionmentioning

confidence: 99%

Protonation and Non-Innocent Ligand Behavior in Pyranopterin Dithiolene Molybdenum Complexes

et al. 2022

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The complex [TEA][Tp*MoIV(O)(S2BMOPP)] (1) [TEA = tetraethylammonium, Tp* = tris(3,5-dimethylpyrazolyl)hydroborate, and BMOPP = 6-(3-butynyl-2-methyl-2-ol)-2-pivaloyl pterin] is a structural analogue of the molybdenum cofactor common to all pyranopterin molybdenum enzymes because it possesses a pyranopterin-ene-1,2-dithiolate ligand (S2BMOPP) that exists primarily in the ring-closed pyrano structure as a resonance hybrid of ene-dithiolate and thione-thiolate forms. Compound 1, the protonated [Tp*MoIV(O)(S2BMOPP-H)] (1-H) and one-electron-oxidized [Tp*MoV(O)(S2BMOPP)] [1-Mo(5+)] species have been studied using a combination of electrochemistry, electronic absorption, and electron paramagnetic resonance (EPR) spectroscopy. Additional insight into the nature of these molecules has been derived from electronic structure computations. Differences in dithiolene C–S bond lengths correlate with relative contributions from both ene-dithiolate and thione-thiolate resonance structures. Upon protonation of 1 to form 1-H, large spectroscopic changes are observed with transitions assigned as Mo(xy) → pyranopterin metal-to-ligand charge transfer and dithiolene → pyranopterin intraligand charge transfer, respectively, and this underscores a dramatic change in electronic structure between 1 and 1-H. The changes in electronic structure that occur upon protonation of 1 are also reflected in a large >300 mV increase in the Mo(V/IV) redox potential for 1-H, resulting from the greater thione-thiolate resonance contribution and decreased charge donation that stabilize the Mo(IV) state in 1-H with respect to one-electron oxidation. EPR spin Hamiltonian parameters for one-electron-oxidized 1-Mo(5+) and uncyclized [Tp*MoV(O)(S2BDMPP)] [3-Mo(5+)] [BDMPP = 6-(3-butynyl-2,2-dimethyl)-2-pivaloyl pterin] are very similar to each other and to those of [Tp*MoVO(bdt)] (bdt = 1,2-ene-dithiolate). This indicates that the dithiolate form of the ligand dominates at the Mo(V) level, consistent with the demand for greater S → Mo charge donation and a corresponding increase in Mo–S covalency as the oxidation state of the metal is increased. Protonation of 1 represents a simple reaction that models how the transfer of a proton from neighboring acidic amino acid residues to the Mo cofactor at a nitrogen atom within the pyranopterin dithiolene (PDT) ligand in pyranopterin molybdenum enzymes can impact the electronic structure of the Mo-PDT unit. This work also illustrates how pyran ring–chain tautomerization drives changes in resonance contributions to the dithiolene chelate and may adjust the reduction potential of the Mo ion.

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“…These are unusual metalloenzymes since they employ second-(Mo) and third-row (W) transition metal ions to perform a myriad of two-electron redox transformations [4]. Furthermore, Moco in these molybdoenzymes is unique in possessing a pyranopterin dithiolene ligand (PDT; also known as molybdopterin) [37,[51][52][53][54][55][56], and Moco is biosynthesized in a complex series of reactions by nine different gene products in bacteria and seven in plants and humans [37,39,[54][55][56][57][58][59][60]. The related pyranopterin W enzymes possess a closely analogous cofactor, the tungsten cofactor, or Tuco [3,61,62].…”

Section: Introductionmentioning

confidence: 99%

Advancing Our Understanding of Pyranopterin-Dithiolene Contributions to Moco Enzyme Catalysis

Burgmayer,

Kirk

2023

Molecules

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The pyranopterin dithiolene ligand is remarkable in terms of its geometric and electronic structure and is uniquely found in mononuclear molybdenum and tungsten enzymes. The pyranopterin dithiolene is found coordinated to the metal ion, deeply buried within the protein, and non-covalently attached to the protein via an extensive hydrogen bonding network that is enzyme-specific. However, the function of pyranopterin dithiolene in enzymatic catalysis has been difficult to determine. This focused account aims to provide an overview of what has been learned from the study of pyranopterin dithiolene model complexes of molybdenum and how these results relate to the enzyme systems. This work begins with a summary of what is known about the pyranopterin dithiolene ligand in the enzymes. We then introduce the development of inorganic small molecule complexes that model aspects of a coordinated pyranopterin dithiolene and discuss the results of detailed physical studies of the models by electronic absorption, resonance Raman, X-ray absorption and NMR spectroscopies, cyclic voltammetry, X-ray crystallography, and chemical reactivity.

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Aiding a Better Understanding of Molybdopterin: Syntheses, Structures, and pKa Value Determinations of Varied Pterin-Derived Organic Scaffolds Including Oxygen, Sulfur and Phosphorus Bearing Substituents

Cited by 4 publications

References 68 publications

Synthesis, Characterization and Chlorination of 4-(Pentyloxy)-7-(prop-2-yn-1-yloxy)pteridin-2-amine

Synthesis, Characterization and Chlorination of 4-(Pentyloxy)-7-(prop-2-yn-1-yloxy)pteridin-2-amine

Protonation and Non-Innocent Ligand Behavior in Pyranopterin Dithiolene Molybdenum Complexes

Advancing Our Understanding of Pyranopterin-Dithiolene Contributions to Moco Enzyme Catalysis

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