Tosylation and acylation of cellulose in 1-allyl-3-methylimidazolium chloride

Tosylation and acylation of cellulose were performed under mild reaction conditions using imidazolium based ionic liquids (ILs) as solvents. The non-degradative nature, lower viscosity, as well as higher solubility of cellulose in [amim]Cl encouraged us to carry out the reactions in this media. The reactions described here were optimised for this particular solvent in order to obtain different cellulose derivatives with high yields, homogeneity and degree of substitution (DS). Two reagents employed for the in situ activation of carboxylic acids were N,N′-carbonyldiimidazole (CDI) and 1-ethyl-3-(3′-dimethylaminopropyl)carbodiimide hydrochloride (EDCI). Final products were characterised by solution and solid-state NMR techniques. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Synthesis of a [60]fullerene‐functionalized poly(vinyl chloride) derivative by stereospecific chemical modification of PVC

The covalent attachment of [60]fullerene (C₆₀) to two poly(vinyl chloride) (PVC) samples with different isotactic content is achieved by direct reaction in o‐dichlorobenzene (o‐DCB) solution in the presence of AIBN. The extent of fullerenation is controlled by varying the C₆₀ feed ratio. The pendant C₆₀‐chemically modified PVC polymers are soluble in tetrahydrofuran (THF) and have been characterized by UV–vis, NMR, FTIR, DSC, TGA, cyclic voltammetry, and SEM. The quantitative microstructural analysis after covalent attachment of the bulky C₆₀ moiety to the PVC has been followed by ¹³C NMR spectroscopy. From the results it can be concluded that the modification of PVC by graft reaction through free radical reaction proceeds by a stereoselective mechanism. This conclusion has been confirmed on the basis of the increase of the glass‐transition temperature (T_g) and the thermal stability of the C₆₀‐chemical modified PVC samples. The fullerenated PVCs obtained show good electron acceptor properties, as evidenced by electrochemical investigations. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5408–5419, 2007     

Synthesis of a [60] fullerene—Functionalized isotactic polypropylene derivative

The covalent attachment of [60] fullerene (C₆₀) to isotactic polypropylene (i‐PP) is achieved by direct reaction in 1,2,4‐trichlorobenzene (TCB) solution in the presence of dicumyl peroxide (DCP). The chemically modified pendant C₆₀/i‐PP polymers are soluble in chlorinated solvents and have been characterized by ultraviolet–visible and fourier transform infrared spectroscopy, scanning electron microscopy, X‐ray diffraction, differential scanning calorimetry, cyclic voltametry, and thermogravimetric analysis. From the results it can be concluded that the modification of i‐PP by grafting via a free‐radical reaction competes with the possibility of chain scission of i‐PP due to the presence of DCP. The functionalized polymers crystallize in the monoclinic crystal modification, and have high crystallinity. The incorporation of C₆₀ significantly enhances the thermal stability of the i‐PP. Electrochemical measurements demonstrate good electron acceptor properties of the fullerenated i‐PP samples. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6722–6733, 2008     

Polycavernoside C and C2, the new analogs of the human lethal toxin polycavernoside A, from the red alga, Gracilaria edulis

Two new analogs of the human lethal toxin polycavernoside A, polycavernoside C and C2 (0.1-0.2 mg for each), were isolated from the red alga, Gracilaria edulis. The relative stereostructure of polycavernoside C and the absolute structure of polycavernoside C2 were determined by spectroscopic analysis and synthesis of the model of their aglycon.     

Synthesis of Laurylchitosan and Its Use in the Separation of Flavonoids from Aleurites moluccana by Matrix Solid-Phase Dispersion

Chitosan was modified with lauroyl chloride to prepare a solid support for the application of matrix solid-phase dispersion (MSPD) for the extraction of flavonoids from the medicinal plant Aleurites moluccana. The laurylchitosan prepared by the homogenous and heterogeneous method, was characterized using analytical methods such as potentiometric titration and infrared spectroscopy. The hydrophobic properties were studied by naphthalene incorporation. The MSPD performance was evaluated by extraction of swertisin and 2″-O-rhamnosylswertisin from the leaves of A. moluccana.     

Super-Magic Complete k-Partite Hypergraphs

 We deal with complete k-partite hypergraphs and we show that for all k≥2 and n≠2,6 its hyperedges can be labeled by consecutive integers 1,2,…,n ^k such that the sum of labels of the hyperedges incident to (k−1) particular vertices is the same for all (k−1)-tuples of vertices from (k−1) independent sets. Received: December 8, 1997 Final version received: July 26, 1999     

Antifungal activity of Annona coriacea Mart. ethanol extracts against the aetiological agents of cryptococcosis

Cryptococcosis is an opportunistic disease with a worldwide distribution. This disease is caused by fungi of the genus Cryptococcus, and its treatment is limited to several antifungals. In this study, the antifungal, cytotoxic and mutagenic properties of ethanol extracts from the bark and leaves of Annona coriacea were evaluated against the standard Cryptococcus species and clinical yeast specimens. Both extracts of A. coriacea showed inhibitory activity of 1.5 mg/mL for all of the yeasts tested. The number of viable cells at the lowest tested concentration was 0.187 mg/mL. The extracts that were tested showed inhibitory activity and reduced the fungal growth of the Cryptococcus gattii species and Cryptococcus neoformans species complexes, suggesting that this plant may be an effective alternative treatment for cryptococcosis.     

Direct observation of the disorder of the methyl group of (R)-1,2-diaminopropane ligand in the quasi-1D bromo-bridged Ni(III) complex by STM

Scanning tunneling microscopy (STM) has been measured in quasi-one-dimensional (Quasi-ID) bromo-bridged Ni(III) complexes. In the STM image of [Ni(pn)2Br]Br2 (pn = (R)-1,2-diaminopropane), the bright spots are fluctuated zigzags. Such a result indicates that the methyl groups of the pn ligands are not arranged on the right- and left-hand alternatively along the chains, but in the domain structures or fluctuated structures. This is the first direct observation of the disorder of the methyl group of pn ligands in real space.     

All Loop Topological String Amplitudes from Chern-Simons Theory

We demonstrate the equivalence of all loop closed topological string amplitudes on toric local Calabi-Yau threefolds with computations of certain knot invariants for Chern-Simons theory. We use this equivalence to compute the topological string amplitudes in certain cases to very high degree and to all genera. In particular we explicitly compute the topological string amplitudes for ² up to degree 12 and ¹× ¹ up to total degree 10 to all genera. This also leads to certain novel large N dualities in the context of ordinary superstrings, involving duals of type II superstrings on local Calabi-Yau three-folds without any fluxes.This research is supported in part by NSF grants PHY-9802709 and DMS-0074329