Prostaglandin E2-bisphosphonate conjugates : potential agents for treatment of osteoporosis.

Conjugates of bisphosphonates (potential bone resorption inhibitors) and prostaglandin E2 (a bone formation enhancer) were prepared and evaluated for their ability to bind to bone and to liberate, enzymatically, free PGE2. The conjugate 3, an amide at C-1 of PGE2 proved to be too stable in vivo while conjugate 6, a thioester, was too labile. Several PGE2, C-15 ester-linked con- jugates (18, 23, 24 and 31) were prepared and conjugate 23 was found to bind effectively to bone in vitro and in vivo and to liberate PGE2 at an acceptable rate. A 4-week study in a rat model of osteoporosis showed that 23 was better tolerated and more effective as a bone growth stimulant than daily maximum tolerated doses of free PGE2

New use for succinylated sugarcane bagasse containing adsorbed Cu2+ and Ni2+ : efficient catalysts for gas-phase n-hexane and n-heptane oxidation reactions.

This study describes the use of succinylated twice-mercerized sugarcane bagasse containing adsorbed Cu2+ or Ni2+ ions from spiked aqueous solutions (2MSBA-Cu and 2MSBA-Ni) as heterogeneous catalysts for the catalytic oxidation of n-hexane and n-heptane in gas phase. To the best of our knowledge, this is the first study in which a spent adsorbent material based on lignocellulose biomass is used in the catalytic oxidation of volatile organic compounds. The adsorbent and spent adsorbent materials were characterized by FTIR, TGA and XRD. The amount of Cu2+ and Ni2+ adsorbed on 2MSBA was 0.49 and 2.49 mmol g?1, respectively. The catalysts were active for total oxidation of n-hexane and n-heptane, even at low temperatures. 2MSBA-Cu exhibited higher catalytic activity than 2MSBA-Ni and surprisingly their performances were comparable or superior to those of some catalysts reported in the literature, including noble metal-based catalysts

Optimization of cellulose and sugarcane bagasse oxidation : application for adsorptive removal of crystal violet and auramine-O from aqueous solution.

Cellulose (Cel) and sugarcane bagasse (SB) were oxidized with an H3PO4-NaNO2 mixture to obtain adsorbent materials with high contents of carboxylic groups. The oxidation reactions of Cel and SB were optimized using design of experiments (DOE) and response surface methodology (RSM). The optimized synthesis conditions yielded Cox and SBox with 4.8 mmol/g and 4.5 mmol/g of carboxylic acid groups, respectively. Cox and SBox were characterized by FTIR, TGA, PZC and solid-state 13C NMR. The adsorption of the model cationic dyes crystal violet (CV) and auramine-O (AO) on Cox and SBox in aqueous solution was investigated as a function of the solution pH, the contact time and the initial dye concentration. The adsorption of CV and AO on Cox was described by the Elovich equation and the pseudo-first-order kinetic model respectively, while the adsorption of CV and AO on SBox was described by the pseudo-secondorder kinetic model. Adsorption isotherms were well fitted by the Langmuir and Konda models, with maximum adsorption capacities (Qmax) of 1117.8 mg/g of CV and 1223.3 mg/g of AO on Cox and 1018.2 mg/g of CV and 682.8 mg/g of AO on SBox. Desorption efficiencies were in the range of 50?52% and re-adsorption capacities varied from 65 to 81%, showing the possibility of reuse of both adsorbent materials

Synthesis and application of a new carboxylated cellulose derivative. Part I : removal of Co2+, Cu2+ and Ni2+ from monocomponent spiked aqueous solution.

A new carboxylated cellulose derivative (CTA) was prepared from the esterification of cellulose with 1,2, 4-Benzenetricarboxylic anhydride. CTA was characterized by percent weight gain (pwg), amount of carboxylic acid groups (nCOOH), elemental analysis, FTIR, TGA, solid-state 13C NMR, X-ray diffraction (DRX), specific surface area, pore size distribution, SEM and EDX. The best CTA synthesis condition yielded a pwg and nCOOH of 94.5% and 6.81 mmol g 1, respectively. CTA was used as an adsorbent material to remove Co2+, Cu2+ and Ni2+ from monocomponent spiked aqueous solution. Adsorption studies were developed as a function of the solution pH, contact time and initial adsorbate concentration. Langmuir model better fitted the experimental adsorption data and the maximum adsorption capacities estimated by this model were 0.749, 1.487 and 1.001 mmol g 1 for Co2+, Cu2+ and Ni2+, respectively. The adsorption mechanism was investigated by using isothermal titration calorimetry. The values of DadsH were in the range from 5.36 to 8.09 kJ mol 1, suggesting that the mechanism controlling the phenomenon is physisorption. Desorption and re-adsorption studies were also performed. Desorption and re-adsorption efficiencies were closer to 100%, allowing the recovery of both metal ions and CTA adsorbent

Oxidized renewable materials for the removal of cobalt(II) and copper(II) from aqueous solution using in batch and fixed-bed column adsorption.

Batch and continuous adsorption of Co2+ and Cu2+ from aqueous solutions by oxidized sugarcane bagasse (SBox) and oxidized cellulose (Cox) were investigated. The oxidation reaction of sugarcane bagasse and cellulose was made with a mixture of H3PO4?NaNO2 to obtain SBox and Cox, with the introduction of high number of carboxylic acid functions, 4.5 and 4.8?mmol/g, respectively. The adsorption kinetics of Co2+ and Cu2+ on SBox and Cox were modeled using two models (pseudo-first-order and pseudo-second-order) and the rate-limiting step controlling the adsorption was evaluated by Boyd and intraparticle diffusion models. The Sips and Langmuir models better fitted the isotherms with values of maximum adsorption capacity of 0.68 and 0.37?mmol/g for Co2+ and 1.20 and 0.57?mmol/g for Cu2+ adsorption on Cox and SBox, respectively. The reuse of both spent adsorbents was evaluated. Adsorption of Cu2+ and Co2+ on SBox in continuous was evaluated using a 22 factorial design with spatial time and initial metal concentration as independent variables and and effective use of the bed as responses. The breakthrough curves were very well described by the Bohart?Adams original model and the values for Co2+ and Cu2+ were 0.22 and 0.55?mmol/g. SBox confirmed to be a promising biomaterial for application on a large scale

Estudo da capacidade de complexa??o de ?ons cu2+ em solu??o aquosa usando celulose modificada com anidrido succ?nico e com poliaminas.

Nesse trabalho foi realizada a prepara??o de novos materiais, a partir da celulose, para complexar ?ons de metais pesados em solu??o aquosa e assim, descontaminar ?guas polu?das por tais metais. Na primeira parte foi realizada a modifica??o qu?mica da celulose usando o anidrido succ?nico. As fun??es carbox?licas introduzidas no material foram usadas para ancorar poliaminas produzindo-se tr?s celuloses modificadas in?ditas. Todos os materiais obtidos foram caracterizados por espectroscopia no infravermelho (IV) e submetidos ? an?lise elementar. A segunda parte do trabalho foi constitu?da da avalia??o do poder de adsor??o das celuloses modificadas obtidas em rela??o aos ?ons Cu2+ em solu??o aquosa. O estudo foi realizado usando a titulometria, um m?todo anal?tico tradicional. Os v?rios materiais mostraram uma capacidade m?xima de complexa??o variando entre 141 e 263 mg de Cu2+ por grama do material modificado. A efici?ncia na complexa??o dos ?ons Cu2+ mostrou-se proporcional ao n?mero de fun??es aminas introduzidas na celulose.This work describes the preparation of new materials, derived from cellulose, to be used as complexing agents for heavy metal ions in aqueous solutions and, hence, to decontaminate waters polluted by such metals. The first part deals with the chemical modification of the cellulose using succinic anhydride. The carboxylic acid functions introduced in the material were used to anchor polyamines resulting in three novel modified celluloses. The materials obtained were characterized by elemental analysis and infrared spectroscopy (IR). The second part of the work features the evaluation of the adsorption capacity of the modified celluloses in relation to Cu2+ ions in aqueous solutions. The study was accomplished by titration, a traditional analytical method. The various materials showed a maximum complexing capacity ranging from 141 to 263 mg of Cu2+ per gram of the modified material. The efficiency for the complexation of Cu2+ ions was proportional to the number of amine functions introduced in cellulose

Adsorption of Cu(II), Cd(II), and Pb(II) from aqueous single metal solutions by succinylated mercerized cellulose modified with triethylenetetramine.

This study describes the preparation of two new chelating materials derived from succinylated mercerized cellulose (cell 1). Cell 1 was activated through two different methods by using diisopropylcarbodiimide and acetic anhydride (to form an internal anhydride) and reacted with triethylenetetramine in order to obtain cell 2 and 4. New modified celluloses were characterized by mass percent gain, concentration of amine functions, elemental analysis, and infrared spectroscopy. Cell 2 and 4 showed degrees of amination of 2.8 and 2.3 mmol/g and nitrogen content of 6.07% and 4.61%, respectively. The capacity of cell 2 and 4 to adsorb Cu2+, Cd2+, and Pb2+ ions from single aqueous solutions were examined. The effect of contact time, pH, and initial concentration of metal ions on the metal ions uptake was also investigated. Adsorption isotherms were well fitted by the Langmuir model. The maximum adsorption capacity of cell 2 and 4 were found to be 56.8 and 69.4 mg/g for Cu2+; 68.0 and 87.0 mg/g for Cd2+; and 147.1 and 192.3 mg/g for Pb2+, respectively

Removal of Ca(II) and Mg(II) from aqueous single metal solutions by mercerized cellulose and mercerized sugarcane bagasse grafted with EDTA dianhydride (EDTAD).

In a previous work, chemically modified cellulose (EMC) and sugarcane bagasse (EMMB) were prepared from mercerized cellulose (MC) and twice-mercerized sugarcane bagasse (MMB) using ethylenediaminetetraacetic dianhydride (EDTAD) as modifying agent. In this work we described in detail the modification of these materials in function of reaction time and EDTAD amount in the reaction media. The resistance of ester bond at pH 1, 2, 11, and 12 was also evaluated by FTIR. The results were used to model the hydrolysis process and a kinetic model was proposed. The modified materials (EMMB and EMC) were used to adsorb Ca2+ and Mg2+ ions from aqueous single solutions. The adsorption isotherms were developed at two pH values. These materials showed maximum adsorption capacities for Ca2+ and Mg2+ ions ranging from 15.6 to 54.1 mg/g and 13.5 to 42.6 mg/g, respectively. The modified material from sugarcane bagasse (EMMB) showed larger maximum adsorption capacities than modified material from cellulose (EMC) for both metals

Stereocontrolled alkylation of chiral pyridinium salt toward a short enantioselective access to 2-alkyl- and 2,6-dialkyl-1,2,5,6-tetrahydropyridines.

Treatment of salts 1a?b with Grignard reagents gives, after reduction of the resulting unstable dihydropyridines 7, the tetrahydropyridines 8a?c, with modest selectivities but in very few steps and under practical conditions. Higher stereoand regioselectivities are obtained with salt 1c which gives the tetrahydropyridines 15a?e. In addition, the dihydropyrid- Introduction The enantioselective synthesis of six-membered nitrogen heterocycles has been the subject of a large number of studies during the past few years due to the interest of these intermediates in natural alkaloid and medicinal chemistry. As a consequence, efficient methods are now available for preparing chiral 2- and 2,6-substituted piperidines.[1] However, few methods are available concerning the corresponding enantiopure substituted tetrahydropyridines.[2] Therefore, we now present a strategy which is briefly summarized in Scheme 1. The main features of this approach are: (a) selective alkylation with Grignard reagents[3?5] of pyridinium salts 1 (Scheme 1), now readily available from chiral primary amines;[6] (b) protonation of the resulting dihydropyridines 2 to give dihydropyridinium salt equivalents 3;[7] (c) additional treatment with a Grignard reagent affording the 2,6-disubstituted tetrahydropyridines 4. Scheme 1. General strategy for the enantioselective construction of substituted tetrahydropyridines The interest of this approach is illustrated by the short synthesis from salt 1c (Scheme 2) of (2)-lupetidin, (1)- solenopsin A and indolizidines (2)-5 and (2)-6, this last synthesis being designed as an example of further ring elaboration of the tetrahydropyridines 4. [a] Institut de Chimie des Substances Naturelles, C.N.R.S. Avenue de la Terrasse, 91198 Gif-Sur-Yvette CEDEX, France Fax: (internat.) 1 33-1/69077247 E-mail: [email protected] [b] Departamento de Quimica, ICEB, Universidad Federal de Ouro Preto, Campus Morro de Cruzeiro, 35400.00, Ouro Preto, MG, Brazil Eur. J. Org. Chem. 2000, 139121399 ? WILEY-VCH VerlagGmbH, D-69451Weinheim, 2000 14342193X/00/040821391 $ 17.501.50/0 1391 ine intermediates 11b cyclize to give the new oxazolidine derivatives 12a?e, which turn out to be good precursors of the 2,6-trans-disubstituted tetrahydropyridines 21a?e. Selective syntheses of (?)-lupetidin, (+)-solenopsin, and indolizidines (?)-5 and (?)-6 are presented as representative examples of applications

Obtaining a new carboxylated derivative of microcrystalline cellulose : an easy and solvent-free synthesis.

O presente trabalho descreve a prepara??o de um novo derivado carboxilado de celulose microcristalina, usando como agente de esterifica??o o ?cido de Meldrum (2,2-dimetil-1,3-dioxano-4,6-diona), sem utiliza??o de solvente. O m?todo produziu um novo material com alto grau de funcionaliza??o. Condi??es otimizadas de s?ntese produziram celulose microcristalina modificada com ?cido de Meldrum (MCCM) com um ganho de massa de 79,9 % e 4.21 mmol/g de fun??es carbox?licas introduzidas ap?s 4 horas de rea??o usando uma propor??o de celulose microcristalina (MCC) para ?cido de Meldrum (MA) de 1:6. MCCM foi caracterizada com sucesso usando FTIR, Difra??o de Raio-X (DRX), an?lise termogravim?trica (TG) e Microscopia Eletr?nica de Varredura (MEV).A solvent-free method for the one-step preparation of a new carboxylatedmicrocrystalline cellulose (MCCM) derivative is described in the present study. The method uses as esterification agent the 2,2-dimethyl-1,3-dioxane-4,6-dione ?Meldru??s a?id) and produced a novel material with high degree of functionalization. Optimized synthesis conditions yielded a MCCM with a weight gain of 79.9% and 4.21 mmol/g of carboxylic acid functions after 4 h of reaction using a microcrystalline cellulose (MCC) to Meldru??s a?id ?MA? ratio of ?:6. MCCM ?as ?hara?terized ?ith success by FTIR, X-ray diffraction (XRD), thermogravimetric (TG) analysis, and scanning electron microscopy (SEM)