Manuel Sánchez-Chaves

Poly (vinyl alcohol) functionalized by monosuccinate groups. Coupling of bioactive amino compounds

Abstract Poly (vinyl alcohol) (PVAL) partially functionalized with monosuccinate groups was obtained by reaction of PVAL with succinic anhydride using triethylamine as catalyst and N-Methyl-2-pyrrolidone as solvent. The structure of the resulting polymers was determined by 1 H and 13 C nuclear magnetic resonance (n.m.r.) spectroscopy. The influence of the type of catalyst, solvent composition and temperature was evaluated. The activation energy was found to be 31.8 kJ/mol. 13 C n.m.r. spectroscopy was used for the determination of the sequence distribution of partially modified PVAL [considered as a vinyl alcohol (VAL)-vinyl succinate (VSU) copolymer]. The results obtained show that VSU units have a random distribution with a slight alternating tendency in the copolymer. High degrees of modification were obtained in the coupling of model bioactive amino compounds (benzocaine, phenethylamine and 2-amino-2-deoxy-D-glucose (glucosamine)) to monosuccinylated PVAL activated with ethyl chloroformate. Interaction experiments between glucosamine-carrying PVAL (PVAL-G) and Concanavalin A (Con A) in a phosphate buffer (pH 7.2) at room temperature showed that PVAL-G interacts with Con A.

Synthesis, characterization and controlled release behaviour of adducts from chloroacetylated cellulose and α-naphthylacetic acid

Abstract Celluloses partially functionalized with chloroacetate groups were obtained by reaction of cellulose with chloroacetyl chloride using pyridine as catalyst and the dimethylacetamide/LiCl system as solvent. 13 C NMR spectra at 75.4 MHz of partially modified cellulose with chloroacetate groups were studied in order to evaluate the selectivity of the reaction of cellulose with chloroacetyl chloride in the homogeneous phase. Analysis of the spectra of ring carbons in the anhydroglucose units shows that the reactivity of the individual hydroxyl groups decreases in the order C-6>C-3>C-2. The coupling of α-naphthylacetic acid to cellulose functionalized with chloroacetate groups was carried out by reaction with their potassium salts or directly in the presence of 1.8-diazabicyclo[5.4.0]-7-undecene. High degrees of modification were obtained by both methods. However, the esterification reaction is somewhat more efficient in the case of the potassium salt. The kinetic results were consistent with a second-order reaction. The hydrolysis in the heterogeneous phase of cellulose–α-naphthylacetic acid adducts showed that the release of the bioactive compound is dependent on the hydrophilic character of the adduct as well as on the pH value of the medium.

13C nuclear magnetic resonance spectral study on the distribution of substituents in relation to the preparation method of partially acetylated dextrans

13C nuclear magnetic resonance (n.m.r.) spectra of partially modified dextrans with acetyl groups prepared by reaction with acetyl chloride or acetic anhydride in the homogeneous phase were analysed at 75.4 MHz. It was found that the distribution of substituents in the anhydroglucose units of these partially acetylated dextrans can be estimated from their ring carbon spectra. The results showed that for acetylated dextrans prepared by reaction with acetyl chloride, the reactivity of individual secondary hydroxyl groups decreases in the order C-2 > C-4 > C-3. For those modified dextrans prepared with acetic anhydride, the ease of acetylation was C-2⋍C-3 >C-4. The results were explained by considering the formation of intramolecular hydrogen bonds as well as by steric considerations.

Functionalization of dextran with chloroacetate groups: immobilization of bioactive carboxylic acids

Abstract Dextrans partially functionalized with chloroacetate groups were obtained by reaction of dextran with chloroacetyl chloride using pyridine as catalyst and the dimethylformamide/LiCl system as solvent. The structure of the resulting polymers was determined by means of infra-red, 1 H and 13 C nuclear magnetic resonance (n.m.r.) spectroscopy. 13 C n.m.r. spectra at 75.4 MHz of partially modified dextran with chloroacetate groups were studied in order to evaluate the selectivity of the reaction of dextran with chloroacetyl chloride in the homogeneous phase. Analysis of the spectra of ring carbons in the anhydroglucose units shows that the reactivity of the individual hydroxyl groups decreases in the order C2 > C3 > C4. The coupling of model bioactive carboxylic acids (α-naphthylacetic and 6-methoxy-α-2-naphthaleneacetic (naproxen)) to dextran functionalized with chloroacetate groups was carried out by reaction with their potassium salts or directly in the presence of 1,8-diazabicyclo[5.4.0]-7-undecene. High degrees of modification were obtained by both methods. However, the esterification reaction is somewhat more efficient in the case of the potassium salts.

Stereochemical configuration of 2‐hydroxyethyl methacrylate/styrene copolymers obtained in N,N′‐dimethylformamide solution over a whole range of conversion

High resolution 1 H-NMR spectra of 2-hydroxyethyl methacrylate (HEMA)-styrene (S) copolymers prepared at low conversion by free radical copolymerization in N,N-dimethylformamide (DMF) solution at 50°C, have been analyzed in terms of sequence distribution and stereoregularity. The Bootstrap effect for the HEMA/S/DMF system was confirmed by comparison of the data obtained with those previously reported for the HEMA/S/bulk system. Reactivity ratios, statistical parameters, and the coisotacticity parameter σ HS = 0.40, estimated at low conversion, were used to describe the observed experimental changes in copolymer composition and triad fraction intensities over a wide range of conversions.

Preparation of dextran-bioactive compound adducts by the direct esterification of dextran with bioactive carboxylic acids

Abstract The direct esterification reaction of dextran with α-naphthylacetic acid (a model bioactive carboxylic acid) is studied in homogeneous phase using pyridine-sulfonyl chloride as catalyst. The structure of the resulting adducts was determined by means of infra-red, 1H nuclear magnetic resonance (n.m.r.) and 13C n.m.r. spectroscopy. The influence of the pyridine concentration, the type of the sulfonyl chloride as well as the temperature was evaluated. Direct esterification reaction was also performed with other bioactive carboxylic acids, such as naproxen and nicotinic acid. 13C n.m.r. spectra at 75.4 MHz of partially modified dextran with α-naphthylacetate groups were studied in order to evaluate the selectivity of the reaction between dextran and α-naphthylacetic acid. Analysis of the spectra of ring carbons in the anhydroglucose units shows that the reactivity of the individual hydroxyl groups decreases in the order C2 > C4 > C3. On the basis of these results a probable mechanism for the reaction is suggested.

Relative reactivities of amylose hydroxyl groups in the reaction with diketene

Abstract 13 C nuclear magnetic resonance (n.m.r.) spectra at 75.4 MHz of partially modified amylose with β-keto ester groups (degree of substitution ( DS ) ranging from 0.52 to 2.42) were studied in order to evaluate the selectivity of the reaction of amylose with diketene in the homogeneous phase. Analysis of the spectra of ring carbons in the anhydroglucose units shows that the reactivity of individual hydroxyl groups decreases in the order C-6>C-3>C-2 for DS values up to ∼1.8. For higher DS values a negative deviation is observed for the hydroxyl group at C-6 and a positive deviation for the hydroxyl groups at C-2 and C-3. The DS values determined by 13 C n.m.r. spectra are in good agreement with those found by chemical analysis.

Synthesis of amidoxime-containing modified dextran

Abstract Dextrans partially modified with cyanoethyl groups were obtained by reaction of dextran with acrylonitrile in alkaline medium. The structure of the resulting polymers was determined by means of infra-red spectroscopy and 1 H and 13 C nuclear magnetic resonance (n.m.r.) spectroscopy. The influence of solvent composition, temperature and acrylonitrile concentration as well as the type and concentration of catalyst was evaluated. 13 C n.m.r. spectra at 75.4 MHz of partially modified dextran with cyanoethyl groups were studied in order to evaluate the selectivity of the reaction of dextran with acrylonitrile in the homogeneous phase. Analysis of the spectra of ring carbons in the anhydroglucose units shows that the reactivity of the individual hydroxyl groups decreases in the order C2 > C4 > C3. Nitrile groups in cyanoethylated dextran were converted to amidoxime groups by reaction with hydroxylamine. The activation energy was found to be 42.7 kJ mol −1 . Preliminary experiments showed the Cu 2+ complex formation ability of amidoximated dextran.

Functionalization of amylose with chloroacetate groups and their derivation with α-naphthylacetic acid. Heterogeneous hydrolytic behaviour of the resulting adducts

Abstract Amylose functionalized with chloroacetate groups was obtained by reaction of amylose with chloroacetyl chloride using pyridine as catalyst and the dimethylformamide/LiCl system as solvent. 13 C-NMR spectra at 75.4 MHz of partially modified amylose with chloroacetate groups were studied in order to evaluate the selectivity of the reaction of amylose with chloroacetyl chloride in the homogeneous phase. Analysis of the spectra of ring carbons in the anhydroglucose units shows that the reactivity of the individual hydroxyl groups decreases in the order C-6 > C-3 > C-2. The coupling of a model bioactive carboxylic acid (a-naphthylacetic acid) to amylose functionalized with chloroacetate groups was carried out by reaction with its potassium salt. High degrees of modification were obtained in all cases. The hydrolysis in the heterogeneous phase of amylose-a-naphthylacetic adducts showed that the release of the bioactive compound is dependent on the sample form and the hydrophilic character of the adduct as well as on the pH value of the medium.

Amphiphilic polymers bearing gluconolactone moieties: synthesis and long side-chain crystalline behavior.

The synthesis and characterization of amphiphilic polymers bearing gluconolactone moieties has been described. In a first step, an unprotected glycomonomer 2-[({[4-(d-gluconamid-N-yl)butyl]amino}carbonyl)oxy]ethyl acrylate, HEAG, has been synthesized. Posterior, this glycomonomer has been copolymerized with methyl methacrylate at different compositions and the kinetic behavior has been also studied calculating the monomer reactivity ratios by Kelen-Tüdös extended equation. In addition, the long side-chain crystalline behavior of these carbohydrate-based copolymers with high composition of glycomonomer has been examined by using conventional and modulated differential scanning calorimetry and X-ray diffraction measurements. At the same time, the phase separation behavior of carbohydrate-based copolymers with lower HEAG content has been determined by their glass transition temperature measurements. Finally, the thermal stability of all these amphiphilic copolymers has been evaluated by thermogravimetric analysis.