1,721,004 research outputs found
Improving efficacy and safety of Avobenzone in cosmetics
No full textThis study concerns the encapsulation of the sunscreen Butyl Methoxydibenzoylmethane (Avobenzone) in several carriers with the aim of increasing its photostability which is one of the main drawbacks for its use in sun products. In this study several microparticles systems based on polymeric and lipidic matrixes have been compared.
The carriers we have studied increase the filter photostability, decrease its release and they can also reduce its eventual percutaneous absorption so assuring a better efficacy and safety of Avobenzone
1,3-Cycloaddition of nitrile oxides in ionic liquids. An easier route to 3-carboxy isoxazolines, potential constrained glutamic acid analogues.
No full textAbstract—Several improvements in the cycloaddition of carboethoxyformonitrile oxide (CEFNO) with different alkenes are
observed in the ionic liquids [bmim][BF4] and [bmim][PF6]. The possibility of obtaining good yields of the corresponding
isoxazolines opens the way towards parallel collections of glutamic acid (Glu) analogues
Synthesis, Crystal Structure and properties of N,N-Dimethyl-N-(6-(benzoyl-4-phenoxy)hexamethylen)-N-n-dodecyl-ammonium bromide: a new substantive UV filter
No full textInprevious paper we have described the synthesis, the substantivity and the antibacterial activity of 4-hydroxy and 2,4-dihydroxy benzophenone derivatives. These properties were affected by the lenght of the n-alkyl chain bonded to the quaternary nitrogen. It would have been of interest to take into consideration also the effect on these properties of the lenght to the methylene chain connecting the oxygen and quaternary nitrogen atoms. In this view we have synthesized N,N-dimethyl-N-(6-(benzoyl-4-phenoxy)hexamethylen)-N-n-dodecil ammonium bromide. Substantivity and antimicrobial properties of this compound have been evaluated and the conformation in the solid state has been determined by single crystal X-ray diffraction. The conformation of the molecule which has been shown to play a fondamental role for the antibacterial activity of these compounds presents an extensive folding of the n-dodecyl chain back towards and along the aromatic moiety. Coiled conformations that have been associated with antibacterial properties and skin irritation phenomena are absent
Sensible Improvements Induced by Ionic Liquids in the Reaction of Modified Carbasugars with Bases for the Building of Constrained Carbanucleosides
No full textStarting from racemic 4-hydroxy-4-methyl-2-
cyclopentenone, a family of enantiopure carbanucleosides
locked in the northern conformation has been synthesized.
The use of ionic liquids was determinant in the last step
resulting in a tangible increase of the yields and dramatic
reduction of reaction times and volumes of organic solvents.
To our knowledge, this is the first example of the use of ionic
liquids in the coupling of carbasugars with heterocyclic
bases
Structure-activity studies in floral odorants.
No full textThis paper reviews the results of our research on the relationships between chemical structure and floral odour, with particular reference to the characteristic note of muguet. Our investigation was aimed at the design and synthesis of substitutes for hydroxycitronellal and other compounds of similar odour, currently employed in perfumery and cosmetics. In order to approach this problem in a systematic way, we have synthesised a great number of tetrahydropyranyl and tetrahydrofuranyl derivatives, as well as other cyclic compounds, that could help modelling the interactions between odorant and receptor proteins, and define the role of each molecular parameter in eliciting the characteristic olfactory note. The compounds exhibiting the best olfactory notes have been used in a conformational analysis, by means of NMR in two different solvents and molecular modelling. A seletion of the odorants synthesised has been also employed in ligand-binding studies, using odorant-binding-proteins purified from nasal mucosa of the bovine and the pig
Comparative conformational and dynamical study of some N-quaternarized UV filters: structure-activity relationships
No full textA comparative conformational and dynamical study of a series of structurally related molecules with UV-filtering properties has been performed in CDCl3 e 2H6DMSO solutions. The main conformers were determined by means of selective spin-lattice proton relaxation rates, carbon spin-lattice relaxation rates and 1D nuclear Overhauser effets. On the basis of these results a possible correlation between conformation and antibacterial activity is discussed
Structural study of ribonucleotide reductase inhibitor hydrazones. Synthesis and X-ray diffraction analysis of a copper(II)-benzoylpyridine-2-quinolinyl hydrazone complex
No full textSingle crystals as yellow needles of N-(4,8-dimethyl-quinolin-2-yl)-N'-(1-pyridin-2-yl-ethylidene)-hydrazine, HL1, 1, and N-(4-methyl-quinolin-2-yl)-N'-(phenyl-pyridin-2-yl-methylene)-hydrazine, HL2, 2, were obtained from methanol (MeOH) and analyzed via X-ray diffraction (XRD). HL2 reacted with copper(II) acetate to produce a dark red powder that gave single crystals of [Cu(L-2)(OOCCH3)] center dot 0.9C(6)H(5)CH(3), 3 center dot 0.9C(6)H(5)CH(3) when recrystallized from toluene. The conformation of the N(quinolinyl,q)C(q)-N(H)N(imine,i)-C-C(pyridine,p)-N(p) grouping is trans,trans,trans,trans or tttt, and ttcc for 1 and 2, respectively, at the solid state, as revealed via single crystal X-ray diffraction. Thus, the structure of 1 has the methyl (hydrazone) group syn to the N-H bond and syn to the N(q) and N(p) atom. On the other side, the structure of 2 is stabilized by a strong intra-molecular N-Hcenter dot center dot center dotN hydrogen bond which involves the pyridyl nitrogen atom. The molecule 1 is almost planar, the torsion angles do not deviate more than 4 from the idealized values of 0 degrees and 180 degrees. In the structure of 2 the pyridyl ring is almost coplanar with the N(q)-C(q)-NH-N(i)-C system, whereas the phenyl (Ph) ring is twisted by ca. 55 degrees. The structure of 3 has the L-2 ligand as deprotonated at the N-N function and in a cttc conformation as opposite to the ttcc one found for pure 2. The metal center is coordinated through N(q), N(i), N(p) and through an oxygen atom from a carboxylate anion. The molecular modeling analysis of 1 and 2 (semi-empirical molecular orbital at Zerner's intermediate neglect of differential overlap (ZINDO/1) level and density functional theory (DFT) methods) gave good agreement with the X-ray structures. Semi-empirical quantum mechanics analysis of 3 allowed to assign the UV-Vis spectrum that is characterized by strong absorptions in the visible, UVA and UVB regions. Owing to the ribonucleotide reductase inhibitory activity of the ligand, to the ascertained anticancer activity shown previously by related copper(II)-hydrazone complexes, and to the oxygen radical scavenger activity of several copper(II)-complexes, 3 is potentially anticancer and anti-inflammatory
Conformational analysis by NMR and molecular modelling for designing new floral odorants.
No full textThe aim of the work was to study the conformational parameters of known floral odorants as a basis for designing new molecules with similar odour and different functional groups. The odorants chosen were hydroxycitronellal and lilial, and a serie of THF and THP ethers that best reproduce the typical note of muguet
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