Carbohydrate-derived polymers combine attractive features like abundant renewable resources, large stereo-chemical diversity and defined functionalization of the carbohydrates. Starting from beta-cyclodextrin, a diazido heptasaccharide was regioselectively obtained in a few steps. It was used as a prepolymer for the A2B2 synthesis of alternating poly(glyco-triazole)s by copper assisted azido alkyne cycloaddition (CuAAC) with two dialkynes of different length and polarity, namely, 1,7-octadiyne and bispropargyl-polyetileneglycol-5. The resulting polymers were completely characterized by FTIR, NMR, MALDI-TOF-MS, SEC MALS, thermal analysis (TG and DSC), and SEM. The alternating insertion of the heptasaccharide and dialkyne in linear polymeric structures was confirmed by NMR and MALDI-TOF experiments. The water-soluble poly(glyco-triazole) containing PEG units had Mn20,640 and Mw 39,650. The thermal properties (Tg = 27-42 degrees C) were close to those of amylose but were influenced by the linker. Therefore, these new poly(glyco-triazole)s could be considered as polysaccharide mimics and alternatives to modified native polysaccharides or brush polymers.

Chitosan is a polymer from renewable biomass, with high abundance and low cost, and therefore widely used in various applications. It is also very interesting, from the chemical point of view, for its high functionality and chirality that allows modifications with the aim of possible interactions with bioactive principles. In this context, chitosan is a polymer widely used in biomedical applications. In this chapter, some chemical modifications that allow its applications in controlled release of biomolecules, such as proteins, nucleic acids, and antibiotics are described.

Poly(amide-triazole) and poly(ester-triazole) synthesized from d-galactose as a renewable resource were applied for the synthesis of nanoparticles (NPs) by the emulsification/solvent evaporation method. The NPs were characterized as stable, spherical particles, and none of their components, including the stabilizer poly(vinyl alcohol), were cytotoxic for normal rat kidney cells. These NPs proved to be useful for the efficient encapsulation of cilostazol (CLZ), an antiplatelet and vasodilator drug currently used for the treatment of intermittent claudication, which is associated with undesired side-effects. In this context, the nanoencapsulation of CLZ was expected to improve its therapeutic administration. The carbohydrate-derived polymeric NPs were designed taking into account that the triazole rings of the polymer backbone could have attractive interactions with the tetrazole ring of CLZ. The activity of the nanoencapsulated CLZ was measured using a matrix metalloproteinase model in a lipopolysaccharide-induced inflammation system. Interestingly, the encapsulated drug exhibited enhanced anti-inflammatory activity in comparison with the free drug. The results are very promising since the stable, noncytotoxic NP systems efficiently reduced the inflammation response at low CLZ doses. In summary, the NPs were obtained through an innovative methodology that combines a carbohydrate-derived synthetic polymer, designed to interact with the drug, ease of preparation, adequate biological performance, and environmentally friendly production.

The use of polymeric composite materials from renewable biomassBiomass has acquired great importance in different and varied fields. Moreover, its application in the biomedical applicationsBiomedical applications has found a fast development in recent years. In this context, this chapter is focused on the use of biocomposites in tissue engineeringTissue engineering and analytical applications. The studied materials include polysaccharidesPolysaccharides such as chitosan, celluloseCellulose, and alginateAlginates, as well as polyhydroxyalcanoates as matrixes, and fillersFillers like nanoparticlesNanoparticles, carbon nanotubesCarbon nanotubes or polymers, among other combinations.

A family of stereoregular poly(amide-triazole)s derived from D-galactose was obtained following several principles of Green Chemistry, namely bio-based starting materials, high yields, benign reaction conditions, energy efficiency, catalysis, atom economy, and chemical degradation. The monomer precursors, the alpha-azido-omega-N-alkynylamide derivatives, were prepared from D-galactose, which was oxidized to D-galactono-1,4-lactone and the secondary hydroxyl groups were protected as isopropylidene acetals. The AB-type azide-alkyne click polymerization led to poly(amide-triazole)s. The Cu(I)-catalyzed polymerization led regioselectively to 1,4-disubstituted triazole ring, and hence to a stereoregular polymer. In contrast, the thermal polymerization produced also 1,5-disubstituted triazole units. The stereoregular polymer underwent acid-promoted chemical degradation, and the degradation products were identified. Moreover, selective removal of the acid labile acetonide moieties led to a partially protected poly(amide-triazole). This polymer was further modified using the "grafting from" approach. Thus, the ROP of caprolactone initiated from the free hydroxyl groups of the polymer led to a linear poly(amide-triazole) grafted with short biodegradable polycaprolactone side-chains. On the other hand, complete HO-deprotection of the monomer gave, after click polymerization, the fully unprotected polymer. The protected poly(amide-triazole)s showed a higher thermal stability compared to the hydroxylated derivatives, which could undergo dehydration processes at lower temperatures. Similarly, the partially protected polymer gave a lower T, value, in agreement with an increasing degree of structural disorder (non-stereoregular materials) and/or lower molecular weight.

α-Azide-ω-alkynyl ester monomers were designed and synthesized in order to obtain hydrolytically degradable polymers. The monomers were prepared from d-galactose, as a renewable resource. Environmentally benign azido-alkyne cycloaddition polymerizations were conducted to afford poly(ester-triazole)s, with complete atom economy. Although polymer formation prevailed under optimized polymerization conditions, variable proportions of cyclic oligomer byproducts were detected. The Cu-catalyzed click polymerization led regioselectively to 1,4-disubstituted triazole linkages, while the thermal, metal-free polymerization produced a random distribution of 1,4- and 1,5-disubstituted triazoles in the polymer backbone. The poly(ester-triazole)s exhibited high molecular weights (M w in the range 35-85 kDa). They were soluble in organic solvents but highly insoluble in water, thus removal of the Cu(i) catalyst was simplified. The polymers were stable up to 300 °C, and had T g values in the range 90-100 °C. The materials were hydrolysed under either basic or strong acid conditions, and the degradation products have been characterized.

A family of linear, carbohydrate-derived oligo(amide-triazole)s has been designed and synthesized. These molecules possess a regular distribution of triazole rings (from one to four) linking the carbohydrate units to give dimer to pentamer derivatives. Their binding to halide anions was qualitatively analyzed by means of NMR spectroscopy and mass spectrometry. All the compounds were able to bind chloride anions, with a stoichiometry that depended on the chain length. The dimer and trimer gave 2:1 host/chloride ratio, while the tetramer and pentamer gave 1:1 complexes. The secondary structure of the oligo(amide-triazole)s was studied using NMR spectroscopy and circular dichroism. These studies showed that the larger host molecules (tetramer and pentamer) adopted a stabilized U-turn and were able to bind just one chloride anion. Only the pentamer displayed a helical conformation, which was slightly distorted in the presence of chloride salts. Interestingly, chloride binding involves not only the triazole-CH but also H atoms from the carbohydrate moieties. These compounds could be applied for chloride sensing by ESI-MS.

1,3-Propanediol (1,3-PDO) is an important chemical widely used in polymer production. This compound has been traditionally obtained by chemical synthesis, but it can also be obtained from bacterial fermentation using glycerol as renewable carbon source. Since 1,3-PDO and glycerol have a similar chromatographic behavior, it is not easy to determine both compounds efficiently in short runs. In this work, we optimized a rapid and simple capillary GC–FID method for the determination of 1,3-PDO and glycerol directly in bacterial culture supernatants. Good peak shapes and high resolution were obtained with no significant tailing. The method was validated in terms of specificity, linearity, precision, accuracy, limit of detection, limit of quantitation, robustness and stability according to USP and ICH guidelines. The method can be applied for the determination of 1,3-PDO and glycerol in different media in less than 5 min with high precision, reproducibility and selectivity. No time-consuming extraction or concentration steps and no significant matrix effects make this method outstanding for glycols determination.

Physico-chemical and rheological characterization of the gum extracted from the endosperm of vinal (Prosopis ruscifolia) seeds was performed. The CG-MS analysis revealed that vinal gum is a galactomannan with a mannose/galactose ratio of 1.6, with traces of arabinose and glucose residues. The structure was further confirmed by C-13 NMR which showed several similarities between vinal gum and guar gum spectra. The viscosity molecular weight was 1.43 +/- 0.04.10(6) Da (obtained from Huggins plot) and the average number molecular weight was 0.7.10(5) Da. Shear continuous rheology studies showed a shear thinning behavior at concentrations higher than 0.04% (w/v) of vinal gum and an apparent viscosity slightly lower than that of guar gum at the same concentration. Mechanical spectra revealed that vinal gum has a typical macromolecular solution behavior with the moduli crossing point that characterized semi-diluted (0.16-0.3% w/v) gum solutions. The present work provides structural, physicochemical and rheological information of a new galactomannan from an abundant and available non-traditional source, being a starting point for food, pharmaceutical or other industrial potential applications of vinal gum. (C) 2015 Elsevier Ltd. All rights reserved.

The Cu(I)-catalyzed, microwave-assisted click polymerization of bio-based α-azide-ω-alkyne monomers afforded, with high regioselectivity, stereoregular poly(amide-triazole)s. The monomers were prepared starting from d-glucono-1,5-lactone as a renewable resource. The synthetic route involves the selective protection of this sugar lactone with formaldehyde to give a gluconic acid derivative, which was subjected to amidation of the carboxylic acid function with alkynylamines (2-propynyl, 3-butynyl, and 4-pentynylamines) and substitution of the primary hydroxyl group by azide. The regioselective click polymerization of these AB-type alkyne/azide monomers led to a series of linear biosourced poly(amide-triazole)s containing mostly (>95%) 1,4-disubstituted triazole linkages. In contrast, the thermal, metal-free click polymerization led to random distribution of 1,4- and 1,5-disubstituted triazoles in the polymer backbone. The length of the methylene chain linked to the amide of the monomer and the cycloaddition regioselectivity strongly affected the properties of the materials, mainly the Tg values, which were unexpectedly high.

Fundamental building blocks used by nature are amalgamated to produce natural-like, yet unnatural, structural entities with multifunctional groups anchored in a single ensemble. For example, hybrid molecules that maintain the basic structure of a carbohydrate have been obtained. This hybrids include amino and carboxyl functional groups, characteristic of amino acids. Diverse arrays of peptidic templates have been employed for the construction of homo- and heterooligomers that behave as peptidomimetics. These molecules are sometimes able to associate themselves spontaneously (self-assembly process) to form complex architectures. The novel materials find useful applications as microelectronics, drug delivery and tissue engineering. The linear oligopeptides are also precursor of cyclic peptoids (carbopeptoids) useful as molecular receptors. We describe herein the synthesis of an amino acid building block starting from inexpensive D-Glucono-1,5-lactone. As the amino containing stereocenter possesses the S configuration, the molecule is combined with Dalanine (R configuration) to give D-alt-L peptides to favor self-assembly processes.

Novel linear carbohydrate-derived [m,n]-polyurethanes are successfully prepared using D-mannitol as renewable and low cost starting material. The key comonomer, 1,6-di-O-phenylcarbonyl-2,3,4,5-tetra-O-methyl-D-mannitol is polymerized with a diamine synthesized from D-mannitol or with alkylenediamines. These polymerization reactions afford, respectively, a [6,6]-polyurethane entirely based on a carbohydrate derivative or [m,n]-polyurethanes constituted by a poly-O-methyl substituted unit alternating with a polymethylene chain. All these polymers are stereoregular, as result of the C2 axis of symmetry of mannitol. The optically active polyurethanes are characterized by standard methods (FTIR, RMN, GPC, TGA, and DSC). Thus, GPC analysis reveals weight-average molecular weights between 18,000 and 25,000 Da. Thermal studies (DSC) indicate that the polymers obtained are amorphous materials with Tg values dependent on the structure and chain length of the diamine constituent. (c) 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013

Aminoalditol 1-amino-1-deoxy-D-sorbitol (1) was readily converted into 2,3,4,5-tetra-O-methyl derivative 5, a key precursor of a sugar-based [n]-polyurethane. For the polymerization, the free amino or primary hydroxyl groups of 5 were selectively activated and employed as starting monomers in two alternative procedures. Thus, the amino function of 5 was converted into the isocyanate derivative by treatment with di-tert-butyltricarbonate, and polymerized in situ in the presence of Zr(IV) acetylacetonate. The resulting poly(1-amino-1-deoxy-2,3,4,5-tetra-O-methyl-D-sorbitol)urethane (8) had a moderate molecular weight and showed the presence of urea units. The alternative synthesis of 8 involved the activation of the free hydroxyl group of 5 as the corresponding phenylcarbonate. The polymerization of this α-amino-ω-phenylcarbonate alditol monomer does not require a metal catalyst. The resulting material exhibited an improved molecular weight and higher purity than that obtained via the isocyanate. [n]-polyurethane 8 was highly soluble in water as well as in common organic solvents (chloroform, acetone, ethyl acetate, etc) and was obtained as an amorphous material which was characterized thermally and spectroscopically.

The oxidation of the free hydroxyl group of methyl 3,4: 5,6-di-O-isopropylidene-D-gluconate 2 or its 2,3: 5,6-di-O-isopropylidene analogue 3, the products of acetonation of D-glucono-1,5-lactone 1, has been attempted by alternative procedures. The oxidation of OH-2 in 2, or OH-4 in 3, with o-iodoxybenzoic acid (IBX) took place to afford the respective 2-keto 4 and 4-keto 7 derivatives in almost quantitative yields. In contrast, the oxidations with pyridinium dichromate were unsuccessful, and those using dimethylsulfoxide-acetic anhydride afforded low yields of 4 or 7. Selective removal of the isopropylidene groups in 4 or 7 with 88% aqueous acetic acid afforded, respectively, the methyl esters 5 or 8; whereas treatment with aqueous trifluoroacetic acid led to the free hexulosonic acids 6 or 9. The tautomeric preferences for the oxidation products 4 and 7, and their derivatives, have been established by C-13 NMR spectroscopy.

Aliphatic [n]-polyurethanes have recently been synthesized from omega-isocyanato-alpha-alkanols or, more traditionally, by cationic ring-opening polymerization of cyclourethanes or by the Bu2Sn(OMe)(2)-promoted polycondensation of omega-hydroxy-alpha-O-phenylurethane alkanes. For the latter procedures, the conditions employed do not seem to be suitable for highly functionalized monomers. Incontrast, the polymerization of omega-amino-alpha-phenylcarbonate alkanes is expected to occur under milder conditions. omega-Amino-alpha-phenylcarbonate alkanes have been synthesized from 6-aminohexanol (1) and 3-aminopropanol (6). The procedure involves the N-Boc protection of the amino group, followed by activation of the alcohol. Removal of the N-Boc affords the corresponding omega-amino-1-O-phenyloxycarbonyloxyalkane hydrochlorides. Other oligomeric comonomers between 1 and 6 have been prepared. The polymerization of these precursors takes place in the absence of metal catalysts to afford the corresponding linear and regioregular [n]-polyurethanes. The procedure described is useful for the preparation of stable omega-amino-alpha-phenylcarbonate alkane derivatives, which possess varied chain lengths between the terminal functions. These monomers yield [n]-polyurethanes having various structures starting from just two aminoalkanols. The polyurethanes were obtained in high yields, with reasonable molecular weight and polydispersity values, and they were characterized spectroscopically and thermally. These studies reveal constitutionally uniform structures that are free of carbonate or urea linkages. (C) 2010 Society of Chemical Industry

The successful analysis by ultraviolet matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (UV-MALDI-TOF MS) of native and hydrolyzed high-methoxylated pectin samples is described. In order to find the optimal conditions for UV-MALDI-TOF MS analysis several experimental variables were studied such as: different UV-MALDI matrices (nor-harmane, 2,5-dihydroxybenzoic acid), sample preparation methods (mixture, sandwich), inorganic salt addition (doping salts, NaCl, KCl, NH(4)Cl), ion mode (positive, negative), linear and reflectron mode, etc. nor-Harmane has never been used as a UV-MALDI matrix for the analysis of pectins but its use avoids pre-treatment of the sample, such as an enzymatic digestion or an acid hydrolysis, and there is no need to add salts, making the analysis easier and faster. This study suggested an alternative way of analyzing native high-methoxylated pectins, with UV-MALDI-TOF MS, by using nor-harmane as the matrix in negative ion mode. The analysis by (1)H and (13)C nuclear magnetic resonance (NMR) spectroscopy of the native and hydrolyzed pectin is also briefly described.

2-Amino-2,3-dideoxy-d-manno-heptonic acid (7) has been synthesized from 2,5,6,7-tetra-O-acetyl-3-deoxy-d-gluco-heptono-1,4-lactone (1), which was readily prepared from d-glycero-d-gulo-heptono-1,4-lactone. O-Deacetylation of 1 followed by treatment with 13:1 (v/v) 2,2-dimethoxypropane/acetone in the presence of p-toluenesulfonic acid gave methyl 3-deoxy-4,5:6,7-di-O-isopropylidene-d-gluco-heptonate (3) as a crystalline product (80% yield). The free hydroxyl group (OH-2) of 3 was mesylated and substituted by azide to give the corresponding azide derivative 5. Hydrogenolysis and further hydrolysis of the ester function of 5 afforded α-amino acid 7 (43% overall yield from 1). Compound 7 is an analog of l-alanine having a polyhydroxy chain attached to C-3. The diastereoisomer of 7 at C-2, 2-amino-2,3-dideoxy-d-gluco-heptonic acid (12) was also prepared from 3, by a route that involved 2,3-dideoxy-2-iodo derivative 8 as a key intermediate.

Aqueous extraction of gametophytic Schizyinenia binderi afforded a polysaccharide composed of galactose and sulfate groups in a molar ratio of 1.0:0.89 together with uronic acids (6.8 wt %) and minor amounts of other neutral sugars. Alkali-treatment of the polysaccharide afforded a polysaccharide devoid of 3,6-anhydrogalactose. C-13 NMR spectroscopy of the desulfated alkali-treated polysaccharide showed a backbone structure of alternating 3-linked beta-D-galactopyranosyl and 4-linked alpha-galactopyranosyl units that are predominantly of the D-configuration and partly of the L-configuration. Methylation, ethylation and NMR spectroscopic studies of the alkali-treated polysaccharide indicated that the sulfate groups are located mainly at positions O-2 of 3-linked beta-D-galactopyranosyl residue and at position O-3 of 4-linked-alpha-galactopyranosyl residues, the latter is partially glycosylated at position O-2. The sulfated galactan from S. binderi exhibited highly selective antiviral activity against Herpes simplex virus types 1 and 2, with selectivity indices (ratio cytotoxicity/antiviral activity) >1000 for all assayed virus strains. This compound was shown to interfere with the initial adsorption of viruses to cells. (C) 2005 Elsevier Ltd. All rights reserved.