A divergent, enantioselective synthetic strategy is reported to produce the non-proteinogenic, biologically active natural amino acids norvaline, 5-hydroxy-4-oxo-L-norvaline, and ɣ-oxonorvaline. These were synthesized in good yields (45-75%) from the common starting material (S)-allylglycine obtained by asymmetric transfer allylation of glycine Schiff base using the Corey catalyst derived from cinchonidine in more than 97% enantiomeric excess.
View Article and Find Full Text PDFDrug therapy for leishmaniasis remains a major challenge as currently available drugs have limited efficacy, induce serious side-effects and are not accessible to everyone. Thus, the discovery of affordable drugs is urgently needed. Chalcones present a great potential as bioactive agents due to simple structure and functionalization capacity.
View Article and Find Full Text PDFThe microalga Chlorella sorokiniana and the microalgae growth-promoting bacteria (MGPB) Azospirillum brasilense have a mutualistic interaction that can begin within the first hours of co-incubation; however, the metabolites participating in this initial interaction are not yet identified. Nuclear magnetic resonance (NMR) was used in the present study to characterize the metabolites exuded by two strains of C. sorokiniana (UTEX 2714 and UTEX 2805) and A.
View Article and Find Full Text PDFA highly regio-, chemo- and stereoselective divergent synthesis of isoindolo- and pyrrolo-fused polycyclic indoles is herein described, starting from 2-formylpyrrole and employing Diels-Alder and Heck arylation reactions. 3-(Benzyl-2-pyrrolyl)acrylates and 4-(pyrrol-2-yl)butenones underwent a highly Diels-Alder cycloaddition with maleimides to furnish octahydropyrrolo[3,4-]indoles, which served as precursors in the regioselective synthesis of aza-polycyclic skeletons via an intramolecular Heck arylation reaction. Through the latter reaction, the 3-(benzyl-2-pyrrolyl)acrylates give rise to 3-(pyrrolo[2,1-]isoindol-3-yl)acrylates.
View Article and Find Full Text PDFThe available drugs for treating Leishmaniasis and American trypanosomiasis have high toxicity and multiple side effects, among other problems. More effective and less toxic treatments are urgently needed. A series of chalcones that contained a prenyloxy or geranyloxy substituent was synthesized and characterized.
View Article and Find Full Text PDFAn efficient and alternative synthesis of exo-imidazolidin-2-one dienes is described. A condensation reaction was carried out with bis-imino derivatives, diacetyl, and triphosgene, affording symmetrically N, N-disubstituted dienes. The use of alkyl methyl α-diketones led to the formation of nonsymmetrical dienes, which underwent isomerization to provide more stable inner-outer-ring dienes under Lewis acid conditions.
View Article and Find Full Text PDFNowadays the industrial chemistry reactions rely on green technologies. Enzymes as lipases are increasing its use in diverse chemical processes. Epoxidized fatty acid methyl esters obtained from transesterification of vegetable oils have recently found applications as polymer plasticizer, agrochemical, cosmetics, pharmaceuticals and food additives.
View Article and Find Full Text PDFHigh-resistance paper was manufactured by laccase-grafting of carboxymethyl cellulose (CMC) and chitosan (CPX) on Kraft pulp fiber. The reaction was mediated in the presence of laccase by one of the following polyphenols in the presence of air: gallic acid (GA), vanillic acid (VA) and catechol (1,2⁻DHB). Enzyme was added at constant loading (24 kg ton), 1% pulp consistency, 0.
View Article and Find Full Text PDFPalladium-based electrocatalysts are widely used in alkaline direct alcohol fuel cells. The synthesis and characterization of carbon-supported bimetallic nanoparticles (NP) of AuPd and AgPd is described using pecan nutshell extract () which serves as both, reducing and the stabilizing agent. This environmentally friendly route generates bimetallic NP for a wide range of applications, including electrocatalysis; since particularly AuPd NP proved to be a potentially suitable electrode material for alkaline direct methanol fuel cells.
View Article and Find Full Text PDFBackground: Malathion (R,S)-diethyl-2-[(dimethoxyphosphorothioyl)sulfanyl]butanedioate is a chiral organophosphorus compound used widely as pesticide for suppression of harmful insects such as mosquitoes. It is well known that in biological systems (R)-malathion is the active enantiomer, therefore a sustainable approach could be the use of only the biologically active enantiomer. The resolution of the commercial racemic mixture to obtain the pure active enantiomer combined with a recycling of the undesired enantiomer through a racemization process could be an attractive alternative to reduce the environmental impact of this pesticide.
View Article and Find Full Text PDFA palladium mediated synthesis of a common synthon for the syntheses of antioxidant analogues of naturally occurring salvianolic acids is presented. The synthetic route may be used to obtain analogues with a balanced lipophilicity/hydrophilicity which may result in potentially interesting LDL antioxidants for the prevention of cardiovascular diseases.
View Article and Find Full Text PDFThe stability of antioxidants in extruded and nixtamalized blue maize flours with calcium hydroxide [Ca(OH)2] and calcium lactate [C6H10O6Ca] were evaluated. Extruded blue maize flours batches were obtained by mixing blue maize flours separately with different Ca(OH)2 (0.1, 0.
View Article and Find Full Text PDFA series of pyrene-fullerene C60 dyads bearing pyrene units (PyFC12, PyFPy, Py2FC12 and PyFN) were synthesized and characterized. Their optical properties were studied by absorption and fluorescence spectroscopies. Dyads were designed in this way because the pyrene moeities act as light-harvesting molecules and are able to produce "monomer" (PyFC12) or excimer emission (PyFPy, Py2FC12 and PyFN).
View Article and Find Full Text PDFBackground: Chalcones are ubiquitous natural compounds with a wide variety of reported biological activities, including antitumoral, antiviral and antimicrobial effects. Furthermore, chalcones are being studied for its potential use in organic electroluminescent devices; therefore the description of their spectroscopic properties is important to elucidate the structure of these molecules. One of the main techniques available for structure elucidation is the use of Nuclear Magnetic Resonance Spectroscopy (NMR).
View Article and Find Full Text PDFWe have prepared all-biopolymer nanocomposite films using lignin as a filler and cellulose triacetate (CTA) as a polymer matrix, and characterized them by several analytical methods. Three types of lignin were tested: organosolv, hydrolytic and kraft, with or without acetylation. They were used in the form of nanoparticles incorporated at 1 wt% in CTA.
View Article and Find Full Text PDFThe coupling of highly oxygenated ortho-alkynylbenzaldehyde derivatives with γ,δ-carbene complexes was evaluated systematically. In all of the electron-rich systems investigated the exclusive product of the reaction is the dihydrophenanthrene derivative. Only the extremely electron withdrawing methanesulfonate group can prevent this process from occurring.
View Article and Find Full Text PDFThe coupling of enyne carbonyl compounds that contain pendant alkene groups with Fischer carbene complexes to afford furans that contain pendant alkene groups is described. Subsequent intramolecular Diels-Alder reactions are effective in select cases, resulting in hydronaphthalene systems after dehydration. Although the Diels-Alder event is thermodynamically unfavorable, the overall transformation of alkene-furans to dihydronaphthalenes is a favorable process.
View Article and Find Full Text PDFA compound containing all of the carbons of the anticancer agent antofine was produced in a single step from the coupling of a gamma,delta-unsaturated carbene complex with a 2-alkynylphenyl ketone derivative. Subsequent conversion to antofine was effected in three steps.
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