Search results for "Zole"
showing 10 items of 2482 documents
Peptide synthesis with 5-amino-1-methyl-1H-[1,2,4]triazole-3-carboxylic acid
2007
Abstract In the search for the peptide synthesis of new potential lexitropsins, starting with methyl 5‐amino‐1‐methyl‐1H‐[1,2,4]triazole‐3‐carboxylate 1a, we synthesized the chloroacetyl derivative of 2a, which was hydrolyzed to acid 2b and ammonolyzed to the peptide 2c. A more effective route was the use of (t‐butoxycarbonyl)glycyl‐benzotriazolide 3 to the acylation 1a, which leads the N/C protected peptide 4. This peptide was selectively N‐deprotected to be the useful segment 5 for further peptide syntheses to the N‐terminus. It was also C‐deprotected, that is hydrolyzed to give peptide 2c for further C‐extension. To the best of our knowledge, this is the first peptide that is a derivativ…
Silanol suppressing potency of alkyl-imidazolium ionic liquids on C18 stationary phases
2011
Residual silanols on C18 columns yield undesirable slow-kinetics ion-exchange interactions with positively charged basic compounds that result in asymmetrical peaks, low efficiencies and long retention times. The purity of the silica employed as supporting material, and the technique used to form the bonded phase, which varies with the brand and manufacturer, give rise to different amounts of residual silanols in the packings, and consequently, different chromatographic performance. One of the most efficient and widespread strategies to reduce or even eliminate the different performance among columns is the addition of a reagent to the mobile phase to block the silanol sites. However, the i…
Base-catalyzed isomerization of 2-isoxazolines enables a two-step enantioselective synthesis of β-hydroxynitriles from enals.
2010
The asymmetric synthesis of β-hydroxynitriles remains a challenge in organic synthesis. Herein we report a convenient synthesis of β-hydroxynitriles from enantiomerically enriched 3-unsubstituted 2-isoxazolines via a base-catalyzed ring-opening reaction that takes place without loss of enantiopurity. In combination with organocatalytic enantioselective synthesis of 3-unsubstituted 2-isoxazolines, the ring-opening enables a short 2-step synthesis of β-hydroxynitriles from α,β-unsaturated aldehydes in high enantiomeric purity.
Spin Transition of 1D, 2D and 3D Iron(II) Complex Polymers The Tug-of-War between Elastic Interaction and a Shock-Absorber Effect
2003
The structures of linear chain Fe(II) spin-crossover compounds of α,β- and α,ω-bis (tetrazol-1-yl)alkane type ligands are described in relation to their magnetic properties. The first threefold interlocked 3-D catenane Fe(II) spin-transition system, [μ-tris(1,4-bis(tetrazol-1-yl)butane-N1,N1′) iron(II)] bis(perchlorate), will be discussed. An analysis is made among the structures and the cooperativity of the spin-crossover behaviour of polynuclear Fe(II) spin-transition materials.
Photo-inhibition of Ab fibrillation mediated by a newly designed fluorinated oxadiazole
2015
Uncontrolled aggregation of amyloid beta peptide (A?) is the main cause of Alzheimer's Disease. Therapeutic approaches of intervention in amyloid diseases include the use of small molecules able to stabilize the soluble A? conformation, or to redirect the amyloidogenic pathway towards non-toxic and non-fibrillar states. Fluorometric measurements revealed that the 3-(4'-trifluoromethylphenyl)-5-(4'-methoxyphenyl)-1,2,4-oxadiazole, when irradiated, is able to interact with monomeric A? peptide readdressing the aggregation pathway toward the formation of amorphous aggregates as evidenced by means of CD, AFM, and SAXS measurements. We hypothesize that this compound, under radiation, forms a rea…
Chemical and pharmaceutical evaluation of the relationship between triazole linkers and pore size on cyclodextrin–calixarene nanosponges used as carr…
2016
Mixed cyclodextrin–calixarene nanosponges were used to prepare some composites with the well known polyphenolic bioactive compounds quercetin and silibinin. The composites were characterized by means of different techniques (UV-vis, FT-IR, microcalorimetry, thermogravimetry), in order to assess their loading and thermal stability. The kinetics of release of the bioactive molecules into aqueous solution were studied at two different pH values (1.0, 6.4), which mimic typical physiological conditions. Finally the possible antiproliferative effects in vitro were assayed towards three triple negative breast cancer cell lines (SUM 149, SUM 159 and MDA-MB-23). Our results point out the role assume…
Supramolecular assemblies of phenyl-pyridyl-triazolopyridine and β-cyclodextrin as sensor of divalent cations in aqueous solution
2014
The chemosensor 3-phenyl-7-(pyrid-2-yl)-[1,2,3]triazolo[1,5-a]pyridine (PhPTP) used in combination with two different cyclodextrins, enable its solubilization and stabilization in aqueous solution. The behavior of the inclusion complex, and its binding ability in both cyclodextrins were investigated by means of absorption and fluorescence spectroscopy. The best results were obtained for PhPTP-DMβCD assembly, and its orientation in the DMβCD nano cavity was obtained by 2D-NMR. This inclusion geometry was confirmed by docking studies. The binary complex was proved as chemosensor upon the presence of different divalent cations in aqueous solutions. The PhPTP-DMβCD system, displays a high sensi…
NMR Study of the (Z)-Phenylhydrazones of 5-Alkyl- and 5-Aryl-3-benzoyl-1,2,4-oxadiazoles: Support for the Interpretation of Kinetic Results on the Re…
2005
An analysis of the 1H, 13C, and 15N NMR substituent chemical shifts (SCSs) of the title compounds in CDCl3 solution has been carried out by using the SCSs of other classes of compounds (arenes, methyl esters or amides), Hammett substituent constants or kinetic data. The results obtained provide information concerning the ground-state electronic distribution of the compounds examined. The results relevant to the carbon and nitrogen atoms of the 1,2,4-oxadiazole ring can be considered of special interest, as the effects of the substit- Introduction For several years our research group has been involved in the use of NMR spectroscopic data (1H, 13C, 15N, and 17O) to obtain information about th…
Benzimidazoles as NMDA Glycine-Site Antagonists: Study on the Structural Requirements in 2-Position of the Ligand
2000
A series of different substituted benzimidazole derivatives has been synthesized and evaluated for the ability to displace [3H]MDL-105,519 to rat cortical membranes. Two benzimidazole-2-carboxylic acids 9 b and 9 c, in this substitution pattern not yet described as glycine antagonists, showed IC50 values of 0.89 microM (9 b) and 38.0 microM (9 c). Replacement of the carboxylate function in 2-position by a sulfonic acid moiety appreciably increased solubility, but decreased the affinity giving evidence for the strong need of the carboxylate group within the ligand. Further structure-activity studies using benzimidazole-2-one derivatives with an acetic acid moiety adjacent to a ring nitrogen …
ChemInform Abstract: Benzimidazoles as NMDA Glycine-Site Antagonists: Study on the Structural Requirements in 2-Position of the Ligand.
2010
A series of different substituted benzimidazole derivatives has been synthesized and evaluated for the ability to displace [3H]MDL-105,519 to rat cortical membranes. Two benzimidazole-2-carboxylic acids 9 b and 9 c, in this substitution pattern not yet described as glycine antagonists, showed IC50 values of 0.89 microM (9 b) and 38.0 microM (9 c). Replacement of the carboxylate function in 2-position by a sulfonic acid moiety appreciably increased solubility, but decreased the affinity giving evidence for the strong need of the carboxylate group within the ligand. Further structure-activity studies using benzimidazole-2-one derivatives with an acetic acid moiety adjacent to a ring nitrogen …