A peptide topological template for the dispersion of [60]fullerene in water

Solubilization of [60]fullerene in water is a major challenge for biological and medical applications. To this purpose in this communication we describe for the first time a new dispersing system based on a peptide topological template. The presence of two carbobenzyloxy groups on the peptide side chains allows \u3c0-\u3c0 interactions with [60]fullerene leading to the formation of stable supramolecular nanocomposites by means of mechanochemical methods. In particular, by high speed vibration milling colloidal dispersions (mean particle diameter 63 nm) containing up to 1.3 mg mL(-1) of [60]fullerene were obtained. Its presence in water was verified through UV-Vis and MALDI-TOF measurements, while its concentration was determined by thermogravimetric analysi

Regio- and stereoselective addition of Grignard and organolithium reagents to 4-hydroxy-2-cyclopentenones

a highly regio- and stereoselective method for the 1,2- or 1,4-addition reactions to 4-hydroxy- 2-cyclopentenones has been devised, which makes use of readily available organolithium and Grignard reagents. This procedure allows for stereochemistry complementary to that observed in the 1,4-addition of organocuprates and makes possible the attachment of aromatic groups to carbons C-2 and C-3 of cyclopentenones 5 or 6 and carbons C-4 and C-5 of cyclopentanones 7, which are of interest for further elaboration into biologically active target

Enantioselective synthesis of gamma,delta-disubstituted beta-hydroxy delta-lactones from furans: Synthesis of (+)-prelactone B and its C-4 epimer

A new method for the enantioselective synthesis of gamma,delta-disubstituted beta-hydroxy delta-lactones (5,6-dialkyl-5,6-dihydropyran-2-ones) is reported and exemplified for (+)-prelactone B and its C-4 epimer. Our approach is based on the ring-enlargement of suitably functionalized optically pure 4-hydroxycyclopentanones, which are readily obtained from chiral 4-hydroxycyclopent-2-enones derived from furans. The procedure is amenable to the large-scale synthesis of the title compounds

Asymmetric synthesis of cyclopentenones with benzylic alpha-quaternary carbon stereogenic centres from furans

A new procedure for the synthesis of cyclopentenones containing benzylic alpha-quaternary carbon stereogenic centres is reported. This method makes use of a one-pot alkylation-elimination sequence from readily available starting materials and simple procedures, which makes it useful for the large-scale preparation of densely functionalised cyclopentanoids. (C) 2004 Elsevier Ltd. All rights reserved

Coordination Chemistry and Applications of Nitrilotris(N-Methylenephenoxy)-Metal ComplexesPATAI'S Chemistry of Functional Groups

Nitrilotris(N-methylenephenols), commonly called triphenolamines (TPA), are highly modular, tetradentate molecules that effectively coordinate to transition metals and main group elements with podand topology. They form chiral complexes with intrinsically well-defined geometries (pentacoordinate trigonal bipyramidal, hexacoordinate octahedral, and, more rarely, trigonal monopyramidal geometries) controlled by the ligand. Nitrilotris(N-methylenephenoxy)\u2013metal complexes have been found to be effective and robust catalysts in a series of important processes like polymerizations (titanium(IV), zirconium(VI), hafnium(VI), germanium(VI), and vanadium(V) complexes), oxygen transfer reactions (titanium(VI), vanadium(V), molybdenum(VI), and nickel(II) complexes), carbon\u2013carbon bond formation (aluminium(III), and titanium(VI) complexes), carbon dioxide fixation (iron(III) complexes), and metathesis (Mo(VI) complexes)

Organic Functionalized Carbon Nanostructures for Functional Polymer-Based Nanocomposites

Carbon nanostructures (CNSs), which are made up of extended sp2-hybridized carbon networks, are largely employed as nanofillers for polymer phases to obtain polymerbased nanocomposites (PNCs). Following their inclusion, the polymer matrices are often improved in many ways, such as enhanced electrical and thermal conductivity, increased stability, and mechanical robustness. The chemical functionalization of the external CNS surfaces with organic substituents is often a key tool for their effective and homogeneous incorporation within a polymer phase, avoiding the formation of aggregates, which can lower the performance of the the final material. This microreview furnishes an overview of PNCs that contain substituted CNSs with organic functionalities. These CNS-based PNCs can be used as organic functional materials in different applications that range from clean energy harvesting and storage to sensing and biomedicine

A powerful chiral counterion strategy for asymmetric transition metal catalysis

Traditionally, transition metal-catalyzed enantioselective transformations rely on chiral ligands tightly bound to the metal to induce asymmetric product distributions. Here we report high enantioselectivities conferred by a chiral counterion in a metal-catalyzed reaction. Two different transformations catalyzed by cationic gold( I) complexes generated products in 90 to 99% enantiomeric excess with the use of chiral binaphthol-derived phosphate anions. Furthermore, we show that the chiral counterion can be combined additively with chiral ligands to enable an asymmetric transformation that cannot be achieved by either method alone. This concept of relaying chiral information via an ion pair should be applicable to a vast number of metal-mediated processes

Regioselective synthesis of trisubstituted cyclopentadienyl ligands from furans

1,2,3- And 1,2,4-trisubstituted cyclopentadienyl manganese tricarbonyl compounds have been synthesized regioselectively from furans following a common synthetic strategy. The key steps include the transformation of furylcarbinols into hydroxycyclopentenones followed by the conjugate addition of Grignard reagents under chelation directed conditions. This affords hydroxycyclopentanones which can be dehydrated to cyclopentenones. These compounds are further elaborated into the final targets by the 1,2-addition of organolithium reagent

Solvent-tunable morphology and emission of pyrene-dipeptide organogels

Two pyrene based organogelators in which the pyrene moiety has been linked to the diphenylalanine dipeptide have been synthesized. We show how the solvent can tune both the morphology and the optical properties of the organogels: spherical aggregates with quenched emission were obtained in acetonitrile, whereas an entangled fibrillar network with enhanced emission was formed in o-dichlorobenzene. Fourier transform infrared spectroscopy, circular dichroismand nuclearmagnetic resonance spectroscopy experiments suggest that both\u3c0\u2013\u3c0 stacking and hydrogen bonding contribute to the formation of the supramolecular networks. Ultraviolet\u2013visible and steady state emission studies demonstrated the formation of I-aggregates in acetonitrile. In contrast, in o-dichlorobenzene, the formation of J-type aggregates leads to assemblieswith enhancedemission. These results give some insight into the important role of the gelling solvent in the morphology of the supramolecular gels and may help in the design of new soft-material

Asymmetric C-C bond formation by the mixed oxidative coupling of 1,1 '-bi-2-naphthyl esters

Asymmetric C-C bond formation was effected by the oxidative coupling of two different ester enolates using (R)-(+)-1,1'-bi(2-naphthol) as a common tether which served to link together both ester moieties in an asymmetric environment. Reduction of the corresponding succinates afforded diastereomerically pure 2,3-disubstituted-1,4-butanediols