Structures of four related 4,5,6,7-tetrahydro-1,2,5-oxadiazolo[3,4-b]pyrazines

Lowe-Ma, Charlotte K.; Fischer, J.; Willer, Rodney L.

doi:10.1107/s0108270189013739

Cited by 13 publications

(17 citation statements)

References 2 publications

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“…Substitution of each CH 2 -CH 2 moiety of the piperazine ring by a furazan ring also leads to lengthening of the N-N bond by 0.02 Å on the average for nitroso derivatives and by 0.04-0.06 Å for nitro derivatives. The data obtained and the trends found are consistent with the results of experimental investigations (1d [28], 1f*, 2d [29], 2f [30], 3a [31]). Comparison of the quantum-chemical calculations for the geometric parameters of the molecules in the gas phase with the X-ray diffraction results for the crystals indicates lengthening (by 1.3-3.6%) of the N-N bonds in the gas phase compared with the solid phase.…”

Section: Calculation Of Geometric Parameters Of the Moleculessupporting

confidence: 94%

“…2). The X-ray diffraction results for compounds 2d [29] and 2f [30] also indicate that in the crystalline state, the piperazine ring has a half-chair form in these compounds.…”

Section: Calculation Of Geometric Parameters Of the Moleculesmentioning

confidence: 81%

“…Thus in the nitroso compounds 1b,d,e, the bond length is 1.34 Å, increasing up to 1.36 Å in compounds 2b,d,e and up to 1.38 Å in the corresponding derivatives of series 3 and 4. Analogous changes were detected by X-ray diffraction; thus the N-N bond length in N,N'-dinitropiperazine (1d) [28] is equal to 1.34 Å, while in N,N'-dinitrosofurazano [3,4-b]piperazine (2d) [29] the bond length increases up to 1.36 Å. In nitro derivatives 1, according to the calculations, the N-NO 2 bond is equal to 1.40 Å (1c), 1.42 Å (1e), and 1.41-1.42 Å (1f), increasing in the corresponding monofurazanoannelated and then the difurazanoannelated derivatives up to 1.44 Å (2c), 1.43 Å (2e), and 1.44 Å (2f).…”

Section: Calculation Of Geometric Parameters Of the Moleculesmentioning

confidence: 99%

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Quantum-chemical study of the structure and thermochemical properties of nitropiperazines and nitrosopiperazines

Korolev

Petukhova

Pivina

et al. 2004

Chem Heterocycl Compd

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We have analyzed the structural, electronic, and thermochemical characteristics and the enthalpies of formation for the compounds in the gas phase and in the solid phase. We have found a correlation between the strength of the N-N bond and the N-N bond length, the pyramidality of the nitrogen atom of the piperazine ring, and the size of the energy gap between the frontier orbitals. Based on calculations by the density functional method, we have carried out a comparative analysis of the thermochemical stability of the compounds in homolytic reactions.

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Section: Calculation Of Geometric Parameters Of the Moleculessupporting

confidence: 94%

“…2). The X-ray diffraction results for compounds 2d [29] and 2f [30] also indicate that in the crystalline state, the piperazine ring has a half-chair form in these compounds.…”

Section: Calculation Of Geometric Parameters Of the Moleculesmentioning

confidence: 81%

Section: Calculation Of Geometric Parameters Of the Moleculesmentioning

confidence: 99%

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Quantum-chemical study of the structure and thermochemical properties of nitropiperazines and nitrosopiperazines

Korolev

Petukhova

Pivina

et al. 2004

Chem Heterocycl Compd

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“…We attribute the electron density on the pterin cofactor to an N-NO modification because NO was the only reactive diatomic species present during crystallization that is capable of forming a stable pterin adduct. Furthermore, the geometry at the N5 position matches that in small molecule crystal structures of the related heterocylic N-NO-pyrazines (43). No significant structural rearrangements are needed to accommodate N-nitrosation of the pterin.…”

Section: Resultsmentioning

confidence: 65%

Nitric-oxide Synthase Forms N-NO-pterin and S-NO-Cys

Rosenfeld

Bonaventura

Szymczyna

et al. 2010

Journal of Biological Chemistry

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Inducible nitric-oxide synthase (iNOS) produces biologically stressful levels of nitric oxide (NO) as a potent mediator of cellular cytotoxicity or signaling. Yet, how this nitrosative stress affects iNOS function in vivo is poorly understood. Here we define two specific non-heme iNOS nitrosation sites discovered by combining UV-visible spectroscopy, chemiluminescence, mass spectrometry, and x-ray crystallography. We detected auto-S-nitrosylation during enzymatic turnover by using chemiluminescence. Selective S-nitrosylation of the ZnS 4 site, which bridges the dimer interface, promoted a dimer-destabilizing order-to-disorder transition. The nitrosated iNOS crystal structure revealed an unexpected N-NO modification on the pterin cofactor. Furthermore, the structurally defined N-NO moiety is solvent-exposed and available to transfer NO to a partner. We investigated glutathione (GSH) as a potential transnitrosation partner because the intracellular GSH concentration is high and NOS can form S-nitrosoglutathione. Our computational results predicted a GSH binding site adjacent to the N-NO-pterin. Moreover, we detected GSH binding to iNOS with saturation transfer difference NMR spectroscopy. Collectively, these observations resolve previous paradoxes regarding this uncommon pterin cofactor in NOS and suggest means for regulating iNOS activity via N-NO-pterin and S-NO-Cys modifications. The iNOS self-nitrosation characterized here appears appropriate to help control NO production in response to cellular conditions. Nitric oxide (NO)4 levels are regulated in vivo at the level of synthesis by three closely related forms of nitric-oxide synthase (NOS): inducible (iNOS), endothelial (eNOS), and neuronal (nNOS) (1). All three NOS enzymes are active only as homodimers and contain two modules: the catalytic oxygenase (NOS ox ) and the electron-supplying reductase (NOS red ) (2). The NOS ox dimer contains two catalytic sites at which the substrate L-arginine binds above the heme (3, 4). The symmetrical NOS ox dimer interface is stabilized by a bridging ZnS 4 cluster and two predominantly buried tetrahydrobiopterin (H 4 B or (6R)-5,6,7,8-tetrahydro-L-biopterin) cofactors, each hydrogen-bonded to one heme (4 -7). Critical differences among the three isozymes include location, regulatory mechanisms, dimer stability, and the amount of NO that is produced (8 -10). iNOS rapidly generates large toxic bursts of NO in vivo and has fewer known mechanisms for halting NO production, whereas eNOS and nNOS produce less NO, are calcium-regulated and contain auto-inhibitory elements (9,11,12).Biological signaling by NO is orchestrated by three interconverting redox-active forms: the free radical (NO ⅐ ), the nitroxide anion (NO Ϫ ), and the nitrosonium cation (NO ϩ ) (13). NO ⅐ binds to metal sites in proteins, while NO ϩ reacts with cysteinyl sulfurs forming S-nitrosylated derivatives (14). S-Nitrosylation is a reversible post-translational modification implicated in protein regulation and signaling within intact cells (15-17). As the major...

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“…[4] General structural modifications leading to advanced HEDMs include:1 )i ntroduction of less sensitive functionalities,e .g., C-NO 2 to replace N-NO 2 ;2 )i ntroduction of polycyclic frameworks,e.g., nitrogen-rich fused rings,bridged rings,a nd caged rings;3 )p lanarization of molecular backbones;a nd 4) introduction of energetic ions to enforce the hydrogen-bonding interactions. [6] In comparison, 2,4,6-trinitro-1,3,5-triazine (3)i sp redicted to have high density and low sensitivity because of the aromatic backbone and C-nitro functionalities,b ut the synthetic work is highly challenging and has not been accomplished yet. However,inthe cases of 1 and 2,the structural modification was accompanied by lowering the packing coefficient, thereby leading to the decrease of crystal density and detonation performance.…”

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confidence: 99%

Polynitro‐Functionalized Dipyrazolo‐1,3,5‐triazinanes: Energetic Polycyclization toward High Density and Excellent Molecular Stability

et al. 2017

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A new fused N-heterocyclic framework, dipyrazolo-1,3,5-triazinane, was synthesized and the physiochemical properties of its derivatives were investigated to evaluate the integrated energetic performance. In contrast to 1,3,5-trinitro-1,3,5-triazinane (RDX) featuring a distorted chair confirmation, polynitro-functionalized dipyrazolo-1,3,5-triazinanes have nearly planar backbones, thereby enhancing the density and thermal stability. Among these new energetic tricyclic compounds, 5 a and 12 show favorable crystal densities of 1.937 g cm and 1.990 g cm at 150 K, respectively, which rank highest in triazinane-based energetic compounds. Additionally, this synthetic approach was carried out to form seven-membered and eight-membered rings, giving rise to tetranitro dipyrazolo-1,3,5-triazepane (5 b) and tetranitro dipyrazolo-1,3,5-triazocane (5 c), respectively.

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Structures of four related 4,5,6,7-tetrahydro-1,2,5-oxadiazolo[3,4-b]pyrazines

Cited by 13 publications

References 2 publications

Quantum-chemical study of the structure and thermochemical properties of nitropiperazines and nitrosopiperazines

Quantum-chemical study of the structure and thermochemical properties of nitropiperazines and nitrosopiperazines

Nitric-oxide Synthase Forms N-NO-pterin and S-NO-Cys

Polynitro‐Functionalized Dipyrazolo‐1,3,5‐triazinanes: Energetic Polycyclization toward High Density and Excellent Molecular Stability

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