Search results for "Tetrazole"
showing 10 items of 70 documents
A DFT study of the asymmetric (S)-5-(pyrrolidin-2-yl)-1H-tetrazole catalyzed Michael addition of carbonyl compounds to nitroalkenes
2007
Abstract The role of the ( S )-5-(pyrrolidin-2-yl)-1 H -tetrazole in the asymmetric organocatalyzed Michael addition of carbonyl compounds to nitroalkenes has been studied using DFT methods at the B3LYP/6-31G ∗∗ computational level. For the C–C bond-formation step, several reactive channels have been analyzed. The B3LYP/6-31G ∗∗ results, which are in reasonable agreement with the experiments, allow us to explain the stereoselectivity and the increase of the reactivity achieved by an intramolecular HB between the acid hydrogen of the tetrazole moiety and one oxygen atom of the nitroalkene.
Improving the photocatalytic H2 evolution activity of Keggin polyoxometalates anchoring copper-azole complexes
2021
Eliminating the use of precious metals as cocatalysts and using visible light are two important aspects in the field of photocatalytic H2 evolution with polyoxometalates (POMs) as photosensitizers. Here we present two new POM-based materials: [CuII5(2-ptz)6(H2O)4(GeW12O40)]·4H2O (1) and [CuI2(ppz)4][H2GeW12O40]·8H2O (2) (2-ptz = 5-(2-pyridyl) tetrazole, ppz = 3-(pyrid-4-yl) pyrazole) synthesized with the Keggin type [GeW12O40]4− (GeW12) polyanion and copper-azole complexes. The optimum photocatalytic H2 evolution rate of compound 1 without a noble metal cocatalyst is 3813 μmol g−1 h−1, which is 7.6 times higher than that of compound 2 and more than 27 times higher than that of bare GeW12 po…
Hirālu piridīna organokatalizatoru izstrāde un pielietojums
2015
Maģistra darba ietvaros tika izstrādāta hirālu DMAP organokatalizatoru sintēze. Iegūto organokatalizatoru aktivitāte tika pārbaudīta tetrazola hemiaminālu dinamiskajā kinētiskajā sadalīšanā.
Fully degradable protein nanocarriers by orthogonal photoclick tetrazole-ene chemistry for the encapsulation and release
2020
The encapsulation of sensitive drugs into nanocarriers retaining their bioactivity and achieving selective release is a challenging topic in current drug delivery design. Established protocols rely on metal-catalyzed or unspecific reactions to build the (mostly synthetic) vehicles which may inhibit the drug's function. Triggered by light, the mild tetrazole–ene cycloaddition enables us to prepare protein nanocarriers (PNCs) preserving at the same time the bioactivity of the sensitive antitumor and antiviral cargo Resiquimod (R848). This catalyst-free reaction was designed to take place at the interface of aqueous nanodroplets in miniemulsion to produce core–shell PNCs with over 90% encapsul…
Site-Specific Dual Labeling of Proteins on Cysteine Residues with Chlorotetrazines
2018
International audience; Dual-labeled biomolecules constitute a new generation of bioconjugates with promising applications in therapy and diagnosis. Unfortunately, the development of these new families of biologics is hampered by the technical difficulties associated with their construction. In particular, the site specificity of the conjugation is critical as the number and position of payloads can have a dramatic impact on the pharmacokinetics of the bioconjugate. Herein, we introduce dichlorotetrazine as a trivalent platform for the selective double modification of proteins on cysteine residues. This strategy is applied to the dual labeling of albumin with a macrocyclic chelator for nucl…
Structure and physical properties of [mu-tris(1,4-bis(tetrazol-1-yl)butane-N4,N4 ')iron(II)] bis(hexafluorophosphate), a new Fe(II) spin-crossover co…
2004
[mu-Tris(1,4-bis(tetrazol-1-yl)butane-N4,N4')iron(II)] bis(hexafluorophosphate), [Fe(btzb)(3)](PF6)(2), crystallizes in a three-dimensional 3-fold interlocked structure featuring a sharp two-step spin-crossover behavior. The spin conversion takes place between 164 and 182 K showing a discontinuity at about T-1/2 = 174 K and a hysteresis of about 4 K between T-1/2 and the low-spin state. The spin transition has been independently followed by magnetic susceptibility measurements, Fe-57-Mossbauer spectroscopy, and variable temperature far and midrange FIR spectroscopy. The title compound crystallizes in the trigonal space group P (3) over bar (No. 147) with a unit cell content of one formula u…
Dynamics of BF 4 - anion reorientation in the spin-crossover compound [Fe(1-n-propyl-1H-tetrazole) 6 ](BF 4 ) 2 and in its Zn II analogue
1999
19 F and 11 B spin-lattice relaxation times were measured in [ Zn ( ptz ) 6 ] ( BF 4 ) 2 and in the spin-crossover compound [ Fe ( ptz ) 6 ] ( BF 4 ) 2 . For both compounds BF 4 - anion reorientation is active above 50 K. For [ Zn ( ptz ) 6 ] ( BF 4 ) 2 , the anion-reorientation dynamics is different in the temperature regions of 50-90 K, 90-120 K, and above 150 K; between 120 and 150 K it changes rapidly reflecting a structural change. In [ Fe ( ptz ) 6 ] ( BF 4 ) 2 the mechanism for the paramagnetic relaxation involving the 19 F nuclei is found to be of the diffusion-limited type according to the theory of Lowe and Tse. The present results prove that the spin-crossover takes place in a dy…
Spin crossover in hexakis(1-(2-chloroethyl)-tetrazole)iron(II) complexes; synthesis and magnetic properties
2002
Abstract The spin-crossover complexes [Fe(teec)6](X)2 (with teec=1-(2-chloroethyl)-tetrazole and X=BF4, ClO4, PF6) possess two iron(II) sites each having a different spin-crossover behaviour. The magnetic behaviour of the complexes obtained by slow crystallisation differs strongly from those obtained by precipitation. This difference results in either a spin crossover of 50% (X=ClO4, crystalline), two gradual steps (X=BF4, PF6), or two steps, of which one is gradual and the other having a thermal hysteresis (X=ClO4 precipitated). Both 57Fe Mossbauer spectroscopy and magnetic susceptibility measurements have been recorded as a function of T. The crystal structure of [Fe(teec)6](BF4)2 has bee…
Role of angiotensin II in arterial pressure and renal hemodynamics in rats with altered renal development: age- and sex-dependent differences
2012
Numerous studies have demonstrated that angiotensin II (ANG II) is involved in hypertension and renal changes occurring as a consequence of an adverse event during renal development. However, it was unknown whether this involvement is sex and age dependent. This study examines whether the increments in arterial pressure (AP) and in the renal sensitivity to ANG II are sex and age dependent in rats with altered renal development. It also evaluates whether the ANG II effects are accompanied by increments in AT1 receptors and oxidative stress. Experiments were performed in 3- to 4- and 10- to 11-mo-old rats treated with vehicle or an AT1 receptor antagonist (ARAnp) during the nephrogenic perio…
NMDA-GABA interactions in an animal model of behaviour: a gating mechanism from motivation toward psychotic-like symptoms
1994
We studied the effects of desipramine, alprazolam, muscimol and dizocilpine (MK-801) (alone or associated with desipramine) in the forced swimming test in rats after long-lasting termination of chronic exposure to vehicle and pentylenetetrazol. Sensitisation with pentylenetetrazol was ineffective in changing immobility time in the forced swimming test compared to vehicle treatment; pentylenetetrazol enhanced the anti-immobility effect of desipramine, abolished the anti-immobility effect of alprazolam and did not affect the anti-immobility effect of muscimol. MK-801 at the dose that did not modify immobility time in vehicle-treated rats and in pentylenetetrazol-treated animals strongly poten…