Search results for "cycles"
showing 10 items of 306 documents
Chemoenzymatic Synthesis of Functional Sialyl LewisX Mimetics with a Heteroaromatic Core
2014
Functional mimetics of the sialyl Lewis(X) tetrasaccharide were prepared by the enzymatic sialylation of a 1,3-diglycosylated indole and a glycosyl azide, which was subsequently transformed into a 1,4-diglycosylated 1,2,3-triazole, by using the trans-sialidase of Trypanosoma cruzi. These compounds inhibited the binding of E-, L-, and P-selectin-coated nanoparticles to polyacrylamide-bound sialyl-Lewis(X) -containing neighboring sulfated tyrosine residues (sTyr/sLe(X) -PAA) at low or sub-millimolar concentrations. Except for E-selectin, the mimetics showed higher activities than the natural tetrasaccharide.
Annelated pyrrolo-pyrimidines from amino-cyanopyrroles and BMMAs as leads for new DNA-interactive ring systems.
2005
The efficient one-pot synthesis of several new tricyclic systems of type 1 and 2, obtained from the reaction of substituted 2-amino-3-cyanopyrroles and 3-amino-4-cyanopyrroles with BMMAs, is reported. The duration and yields of the reaction strongly depend on the reactivity of the starting pyrrole and on the size of the ring to be formed. Mechanist features of the reaction were investigated and proposed by studying also the reactivity of a 3-aminopyrrole-2,4-dicyano substituted. The method reported represents the first example of the use of BMMA reagents in combination with pyrrole derivatives and allows an easy and versatile entry to a large number of hitherto unknown pyrrolo-pyrimidines f…
A deep insight into the mechanism of the acid-catalyzed rearrangement of the Z-phenylhydrazone of 5-amino-3-benzoyl-1,2,4-oxadiazole in a non-polar s…
2010
The conversion of the Z-phenylhydrazone of 5-amino-3-benzoyl-1,2,4-oxadiazole (1a) into the relevant 1,2,3-triazole (2a) has been quantitatively studied in toluene in the presence of several halogenoacetic acids (HAAs, 3a–h). Again, the occurrence of two reaction pathways has been pointed out: they require one or two moles of acid, respectively, thus repeating the situation previously observed in the presence of trichloroacetic acid. The observed rate constant ratios (kIII/kII) are only slightly affected by the nature of the acid used. To gain a deeper insight into the action of the acids used we have measured the association constants of the HAAs (3a–h) with 4-nitroaniline (4) in toluene. …
Synthesis and preliminary antibacterial evaluation of Linezolid-like 1,2,4-oxadiazole derivatives
2012
In the present study the synthesis of new Linezolid-like molecules has been achieved by substitution of the oxazolidinone central heterocyclic moiety with a 1,2,4-oxadiazole ring. Two series of 1,2,4-oxadiazoles, bearing different side-chains and containing a varying number of fluorine atoms, were synthesized and preliminarily tested for biological activity against some Gram-positive and Gram-negative bacteria using Linezolid and Ceftriaxone as reference drugs
Iron(III) bis(pyrazol-1-yl)acetate based decanuclear metallacycles: synthesis, structure, magnetic properties and DFT calculations
2016
The synthesis, structural aspects, magnetic interpretation and theoretical rationalizations for a new member of the ferric wheel family, a decanuclear iron(III) complex with the formula [Fe10(bdtbpza)10(μ2-OCH3)20] (1), featuring the N,N,O tridentate bis(3,5-di-tert-butylpyrazol-1-yl)acetate ligand, are reported. The influence of the steric effect on both the core geometry and coordination mode is observed. Temperature dependent (2.0–300 K range) magnetic susceptibility studies carried out on complexes 1 established unequivocally antiferromagnetic (AF) interactions between high-spin iron(III) centers (S = 5/2), leading to a ground state S = 0. The mechanism of AF intramolecular coupling was…
Mononuclear rearrangement of heterocycles in zwitterionic micelles of amine oxide surfactants.
2012
Abstract Rate constants for the mononuclear rearrangement (MRH) of Z -phenylhydrazones of some 5-substituted-3-benzoyl-1,2,4-oxadiazoles in water have been measured in the presence of zwitterionic micelles. The use of micellized N -tetradecyl- N , N -dimethylamineoxide (C 14 DMAO) as the reaction medium allowed to solubilize the otherwise water-insoluble oxadiazoles. Micellar rate effects were analyzed by using a simple pseudo-phase model and compared with those obtained in non-ionic micelles (Triton X-100). Evidence that both the rate of the rearrangement reaction and the binding of the substrates to the micelles are mainly governed by substrate hydrophobicity is obtained. The disagreement…
Acid- and Base-Catalysis in the Mononuclear Rearrangement of Some (Z)-arylhydrazones of 5-Amino-3-benzoyl-1,2,4-oxadiazole in Toluene: Effect of Subs…
2011
The reaction rates for the rearrangement of eleven (Z)-arylhydrazones of 5-amino-3-benzoyl-1,2,4-oxadiazole 3a-k into the relevant (2-aryl-5-phenyl-2H-1, 2,3-triazol-4-yl)ureas 4a-k in the presence of trichloroacetic acid or of piperidine have been determined in toluene at 313.1 K. The results have been related to the effect of the aryl substituent by using Hammett and/or Ingold-Yukawa-Tsuno correlations and have been compared with those previously collected in a protic polar solvent (dioxane/water) as well as with those on the analogous rearrangement of the corresponding (Z)-arylhydrazones of 3-benzoyl-5-phenyl-1,2,4-oxadiazole 1a-k in benzene. Some light can thus be shed on the general di…
Volume change behaviour of a compacted scaly clay during cyclic suction changes
2010
The research presented in this paper focuses on the investigation and modelling of the volume change response of compacted tectonised clay samples subjected to several wetting and drying cycles in controlled-suction oedometers. Oedometer tests were carried out under different values of constant vertical net stress, and wetting and drying cycles were performed varying applied matric suction between 10 and 800 kPa. The investigation was complemented with a study of the material microstructure to support the interpretation of the overall mechanical response. At a microscopic level, the material is characterized by different types of particle assemblages, scales, and clay aggregates. One of th…
Transportation and sustainable development in a mid-size French city, Dijon
2011
International audience
Synthesis of Isoxazoline Derivatives through Boulton–Katritzky Rearrangement of 1,2,4-Oxadiazoles
2013
The base-induced rearrangement of 1,2,4-oxadiazoles into isoxazoline derivatives is reported. This represents the first example of a three-atom side-chain rearrangement that involves a saturated CCO side chain at C-3 of the oxadiazole. Nonaromatic 3-amino-isoxazoline derivatives are obtained in good yields. Interestingly, this reaction occurs through the rearrangement of aromatic oxadiazoles to form less stable bonds than those that are broken.