Regioselective end‐functionalization of polylactide oligomers with D‐glucose and D‐galactose

D ‐glucose and D ‐galactose end‐functionalized polylactide oligomers were synthesized by controlled ring‐opening polymerization of lactide using aluminium triisopropoxide, triethylaluminium or stannous octoate as promoter. Accordingly, two selectively protected monosaccharides were studied as co‐initiators, either 1,2;5,6‐di‐O‐isopropylidene‐α‐D ‐glucofuranose (1) and 1,2;3,4‐di‐O‐isopropylidene‐α‐D ‐galactopyranose (2). In contrast to what is known in polymerization of ?‐caprolactone, both protected monosaccharides proved to be efficient co‐initiators and yielded end‐functionalized polylactide chains with controlled regioselectivity (C‐3 or C‐6 linkage), predictable molecular weights and narrow molecular weight distributions. © 2003 Society of Chemical Industry     

Semicontinuous emulsion copolymerization of 3‐O‐methacryloyl‐1,2:5,6‐di‐O‐isopropylidene‐α‐D‐glucofuranose (3‐MDG) and butyl acrylate (BA). Monomer feed addition

New polymer colloids based on the saccharide monomer, using of 3‐O‐methacryloyl‐1,2:5,6‐di‐O‐isopropylidene‐α‐D ‐glucofuranose (3‐MDG), were prepared by semicontinuous emulsion polymerization, a widely used industrial process. The copolymerization of 3‐MDG and butyl acrylate (BA), by the monomer‐addition technique, at 70°C, using sodium persulfate (Na₂S₂O₈) as an initiator, was investigated. The influence of some reaction parameters, such as the type and concentration of the surfactants as well as the monomer addition rate (R_m) on the polymerization rate (R_p), the colloidal properties, and the stability of the latexes, was studied. It was found that under starved‐feed conditions the polymerization rate and the particle size (D) increased with an increasing rate of monomer addition. The weight‐average molecular weight (M _w) also increased by enhancing R_m and a narrower molecular weight distribution was obtained. Furthermore, the type and the concentration of the surfactants strongly influenced the particle size and its distribution. The effect of the seed stage on the particle size and its distribution was also investigated. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2091–2102, 2003     

New Trifluoromethyl Substituted 1,2, 3‐Triazoles Linked to D‐Galactose and D‐Gulose

The title compounds were synthesized by 1,3‐dipolar cycloaddition of 3,3,3‐trifluoropropinyl benzene ( 2 ) to the azido sugars 2,3,4,6‐tetra‐O‐acetyl‐β‐D ‐galactopyranosyl azide ( 1 ), 6‐O‐acetyl‐4‐O‐cyclohexylcarbamoyl‐2,3‐O‐(2,2,2‐trichloroethylidene)‐β‐D ‐gulopyranosyl azide ( 6 ), 6‐azido‐6‐deoxy‐1,2:3,4‐di‐O‐isopropylidene‐α‐D ‐galactopyranose ( 12 ), and methyl 6‐azido‐4‐O‐cyclohexylcarbamoyl‐6‐deoxy‐2,3‐O‐(2,2,2‐trichloroethylidene)‐β‐D ‐gulopyranoside ( 16 ), respectively. Because of the dissymmetry of the dipolarophile 2 , always two regioisomeric products were obtained, the nucleoside‐analogous compounds 3/4 (from 1 ) and 7/8 (from 6 ), respectively, and the reversed nucleosides 13/14 (from 12 ) and 17/18 (from 16 ), respectively. Protecting group chemistry like transesterification, deacetalation, hydrodechlorination is demonstrated in some cases. Thus, the trichloroethylidene derivatives 7, 8, 17, and 18 were converted into the corresponding ethylidene derivatives ( 9, 10, 19, 20 ) by treatment with tributylstannane/AIBN. An X‐ray analysis is given for the 1‐(2,3,4,6‐tetra‐O‐acetyl‐β‐D ‐galactopyranosyl)‐4‐trifluoromethyl‐5‐phenyl‐1,2,3‐triazole ( 4 ) and for the 1‐[6‐O‐acetyl‐4‐O‐cyclohexylcarbamoyl‐2,3‐O‐(2,2,2‐trichloroethylidene)‐β‐D ‐gulopyranosyl]‐4‐trifluoromethyl‐5‐phenyl‐1,2,3‐triazole ( 7 ).     

D‐isosorbide and 1,3‐propanediol as plasticizers for starch‐based films: Characterization and aging study

In the present work, D‐isosorbide and 1,3‐propanediol are proposed as alternative plasticizers obtained from renewable resources. Plasticized starch films were prepared by solvent casting method. The influence of using different “green” plasticizers in the final properties of starch‐based films was analyzed. Besides, the characterization of the films was also performed after storage time in order to evaluate the effect of the plasticizer on aging. UV‐spectrophotometry results showed better optical properties for both glycerol and D‐isosorbide films with higher transparency. The thermal and mechanical properties resulted influenced by the nature of the plasticizer. It was demonstrated that water vapor permeability was governed by the starch‐water interactions, whereas the oxygen permeability depended on the plasticizer's nature. The storage time affected the surface, mechanical, and thermal properties of the plasticized starch films. Atomic force microscopy results concluded that the topography of the films changed due to aging. The use of D‐isosorbide as plasticizer reduced the evolution of the mentioned properties and enhanced the reliability of the material. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44793.     

Syntheses and biological activities of polymers containing methacryloyl‐2‐oxy‐1,2,3‐propanetricarboxylic acid or 5‐fluorouracil

A series of novel copolymers, poly(methacryloyl‐2‐oxy‐1,2,3‐propanetricarboxylic acid‐co‐exo‐3,6‐epoxy‐1,2,3,6‐tetrahydrophthalic acid) [poly(MTCA‐co‐ETAc)], poly(methacryloyl‐2‐oxy‐1,2,3‐propanetricarboxylic acid‐co‐hydrogenethyl‐exo‐3,6‐epoxy‐1,2,3,6‐tetrahydrophthalate) [poly(MTCA‐co‐HEET)], and poly(methacryloyl‐2‐oxy‐1,2,3‐propanetricarboxylic acid‐co‐α‐ethoxy‐exo‐3,6‐epoxy‐1,2,3,6‐tetrahydrophthaloyl‐5‐fluorouracil) [poly(MTCA‐co‐EETFU)], were prepared from corresponding monomers by photopolymerizations at 25°C for 48 h. The polymers were identified by FTIR, ¹H‐NMR, and ¹³C‐NMR spectroscopies. The number‐average molecular weights of the fractionated polymers determined by GPC were in the range from 9400 to 14,900 and polydispersity indices were 1.2–1.4. The in vitro IC₅₀ values of polymers against mouse mammary carcinoma (FM3A), mouse leukemia (P388), and human histiocytic lymphoma (U937) as cancer cell lines and mouse liver cells (AC2F) as a normal cell line were much higher compared to that of 5‐fluorouracil (5‐FU). The in vivo antitumor activities of monomers and polymers against mice bearing sarcoma 180 tumor cell line were better than those of 5‐FU. The inhibition of DNA replication and antiangiogenesis activities of MTCA and copolymers were better compared to those of 5‐FU. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 57–64, 2004     

Synthesis and antitumour and antiangiogenesis activity of polymers containing methacryloyl‐2‐oxy‐1,2,3‐propane tricarboxylic acid

A new monomer, methacryloyl‐2‐oxy‐1,2,3‐propane tricarboxylic acid (MTCA), was synthesized from citric acid and methacrylic anhydride. Poly(methacryloyl‐2‐oxy‐1,2,3‐propane tricarboxylic acid) and poly(methacryloyl‐2‐oxy‐1,2,3‐propane tricarboxylic acid)‐co‐(maleic anhydride) were prepared by radical polymerizations. Terpoly(methacryloyl‐2‐oxy‐1,2,3‐propane tricarboxylic acid–maleic anhydride–furan) was obtained by in situ terpolymerization of MTCA and exo‐3,6‐epoxy‐1,2,3,6‐tetrahydrophthalic anhydride. The synthesized samples were identified by FTIR, ¹H NMR and ¹³C NMR spectroscopies. The number‐average molecular weights of the fractionated polymers determined by GPC were in the range 14 900–16 600 and polydispersity indices were less than 1.14. The in vitro IC₅₀ values of the monomer and polymers against cancer and normal cell lines were much higher than those of 5‐fluorouracil (5‐FU). The in vivo antitumour activities of the synthesized samples at a dosage of 0.8 mg kg⁻¹ against mice bearing the sarcoma 180 tumour cell line decreased in the order terpoly(MTCA‐MAH‐FUR) > poly(MTCA‐co‐MAH) > poly(MTCA) > MTCA > 5‐FU. The synthesized samples inhibited DNA replication and angiogenetic activity more than did 5‐FU. © 2001 Society of Chemical Industry     

Identification and Characterization of D‐Succinylase,and a Proposed Enzymatic Method for D‐Amino Acid Synthesis

Chiral amino acids are important intermediates for the pharmaceutical industry. We have developed a novel one‐pot enzymatic method for D ‐amino acid synthesis by the dynamic kinetic resolution of N‐succinyl‐dl ‐amino acids using D ‐succinylase (DSA) and N‐succinylamino acid racemase (NSAR, EC 4.2.1.113). The DSA from Cupriavidus sp. P4‐10‐C, which hydrolyzes N‐succinyl‐D ‐amino acids enantioselectively to their corresponding D ‐amino acids, was identified for the first time by screening soil microorganisms. Subsequently, the DSA gene was cloned and overexpressed in Escherichia coli. DSA was shown to comprise two subunits with molecular masses of 26 kDa and 60 kDa. Additionally, the NSAR gene from Geobacillus stearothermphilus NCA1503, which racemizes N‐succinylamino acids, was also cloned and overexpressed in E. coli. The highly purified DSA and NSAR prepared from each recombinant E. coli were characterized and used for D ‐amino acid synthesis. A one‐pot enzymatic method converted 100 mM N‐succinyl‐dl ‐phenylalanine to D ‐phenylalanine in 91.1% conversion with 86.7% ee. This novel enzymatic method may be useful for the industrial production of many D ‐amino acids.

     

Hydroxybenzaldoximes Are D‐GAP‐Competitive Inhibitors of E. coli 1‐Deoxy‐D‐Xylulose‐5‐Phosphate Synthase

1‐Deoxy‐D ‐xylulose 5‐phosphate (DXP) synthase is the first enzyme in the methylerythritol phosphate pathway to essential isoprenoids in pathogenic bacteria and apicomplexan parasites. In bacterial pathogens, DXP lies at a metabolic branch point, serving also as a precursor in the biosynthesis of vitamins B1 and B6, which are critical for central metabolism. In an effort to identify new bisubstrate analogue inhibitors that exploit the large active site and distinct mechanism of DXP synthase, a library of aryl mixed oximes was prepared and evaluated. Trihydroxybenzaldoximes emerged as reversible, low‐micromolar inhibitors, competitive against D ‐glyceraldehyde 3‐phosphate (D ‐GAP) and either uncompetitive or noncompetitive against pyruvate. Hydroxybenzaldoximes are the first class of D ‐GAP‐competitive DXP synthase inhibitors, offering new tools for mechanistic studies of DXP synthase and a new direction for the development of antimicrobial agents targeting isoprenoid biosynthesis.     

2D‐ and 3D‐Photoluminescence Imaging of Eu(III) Embedded in CeO2 Nanomatrix

2D‐ and 3D‐photoluminescence characteristics of Eu(III) doped in CeO₂ nanoparticles were fully imaged for the first time. Their fundamental natures were also examined by scanning electron microscopy (SEM), X‐ray diffraction (XRD) crystallography, and UV–visible absorption spectroscopy. The magnetic dipole ⁵D₀ → 7F₁ transition was dominated by an indirect transition associated with a O^2?–Ce⁴⁺ charge‐transfer band of CeO₂. The electric dipole ⁵D₀ → ⁷F₂ transition was dominated by a direct transition of Eu(III), indicating that Eu(III) replaces Ce(IV) at octahedral sites (O_h and O) with and without an inversion center. Upon annealing, the photoluminescence intensity caused by direct transition was dramatically decreased, whereas that induced by indirect transition was greatly enhanced. These findings indicate that charge transfer to the Eu(III) at the octahedral (O_h) site with the inversion center is more efficient than that to the Eu(III) site without an inversion center. The absolute quantum yield for the 10 mol% Eu(III)–CeO₂ was found to be ? = 0.007 at an excitation wavelength of 350 nm. The photoluminescence of Tb‐doped CeO₂ was briefly discussed for comparison.     

Characterization of a Galactosynthase Derived from Bacillus circulans β‐Galactosidase: Facile Synthesis of D‐Lacto‐ and D‐Galacto‐N‐bioside

Glycosynthases—retaining glycosidases mutated at their catalytic nucleophile—catalyze the formation of glycosidic bonds from glycosyl fluorides as donor sugars and various glycosides as acceptor sugars. Here the first glycosynthase derived from a family 35 β‐galactosidase is described. The Glu→Gly mutant of BgaC from Bacillus circulans (BgaC‐E233G) catalyzed regioselective galactosylation at the 3‐position of the sugar acceptors with α‐galactosyl fluoride as the donor. Transfer to 4‐nitophenyl α‐D ‐N‐acetyl‐glucosaminide and α‐D ‐N‐acetylgalactosaminide yielded 4‐nitophenyl α‐lacto‐N‐biose and α‐galacto‐N‐biose, respectively, in high yields (up to 98 %). Kinetic analysis revealed that the high affinity of the acceptors contributed mostly to the BgaC‐E233G‐catalyzed transglycosylation. BgaC‐E233G showed no activity with β‐(1,3)‐linked disaccharides as acceptors, thus suggesting that this enzyme can be used in “one‐pot synthesis” of LNB‐ or GNB‐containing glycans.     

Lipase‐catalyzed acidolysis and phospholipase D‐catalyzed transphosphatidylation of phosphocholine

Two approaches on enzymatic phospholipid modification were studied: (1) transphosphatidylation of the 1,2‐dilauroyl‐sn‐glycero‐3‐phosphocholine (DLPC) and ethanolamine in biphasic and anhydrous organic solvent systems by phospholipase D (PLD) and (2) incorporation of oleic acid into the sn1‐position of DLPC in organic solvents with different immobilized lipases at controlled water activity. First, DLPC was chemically synthesized from glycerophosphocholine and lauric acid. Next, PLD‐catalyzed head group exchange of DLPC with ethanolamine was studied using an enzyme from Streptomyces antibioticus expressed recombinantly in E. coli. A comparison of the free PLD with the biocatalyst activated by a salt‐activation technique using KCl showed that the salt‐activated enzyme (PLD‐KCl) was 10–12 folds more active based on the amount of protein used. Thus, DLPC was quantitatively converted to 1,2‐dilauroyl‐sn‐glycero‐3‐phosphoethanolamine in an anhydrous solvent system within 12 h at 60 °C. For the acidolysis of DLPC with oleic acid, among the four lipases studied (CAL‐B, Lipozyme TL IM, Lipozyme RM IM and lipase D immobilized on Accurel EP‐100), Lipozyme TL IM showed the highest activity and incorporation of oleic acid. A quantitative incorporation was achieved at 40 °C using a 8‐fold molar excess of oleic acid in n‐hexane at a water activity of 0.11.     

One‐Pot Cascade Reactions using Fructose‐6‐phosphate Aldolase: Efficient Synthesis of D‐Arabinose 5‐Phosphate,D‐Fructose 6‐Phosphate and Analogues

One‐pot multienzymatic reactions have been performed for the synthesis of 1‐deoxy‐D ‐fructose 6‐phosphate, 1,2‐dideoxy‐D ‐arabino‐hept‐3‐ulose 7‐phosphate, D ‐fructose 6‐phosphate and D ‐arabinose 5‐phosphate. The whole synthetic strategy is based on an aldol addition reaction catalysed by fructose‐6‐phosphate aldolase (FSA) as a key step of a three or four enzymes‐catalysed cascade reaction. The four known donors for FSA – dihydroxyacetone (DHA), hydroxyacetone (HA), 1‐hydroxy‐2‐butanone (HB) and glycolaldehyde (GA) – were used with D ‐glyceraldehyde 3‐phosphate as acceptor substrate. The target phosphorylated sugars were obtained in good to excellent yields and high purity.     

Boron removal by liquid‐phase polymer‐based retention technique using poly(glycidyl methacrylate N‐methyl D‐glucamine)

The removal of boron was analyzed by liquid‐phase polymer based retention (LPR) technique using washing and enrichment method. The extracting reagents were water‐soluble polymers (WSPs) containing quaternary ammonium salts and N‐methyl‐D ‐glucamine (NMG) groups. The removal experiments of boron using the washing method were conducted at 1 bar of pressure by varying pH, polymer:boron molar ratio, and concentrations of interfering ions (chloride and sulfate). The results showed higher retention capacity for boron (60%) at pH 10 with the polymer containing NMG group. The optimal polymer:boron molar ratio was 40 : 1. Selectivity experiments showed that the presence of interfering ions did not affect the boron removal capacity. The maximal boron retention capacity was determined by the enrichment method, obtaining a value of 12 mg B/g‐polymer. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Synthesis,characterization, and application of novel amphiphilic poly(D‐gluconamidoethyl methacrylate)‐b‐polyurethane‐b‐ poly(D‐gluconamidoethyl methacrylate) triblock copolymers

Novel amphiphilic ABA‐type poly(D ‐gluconamidoethyl methacrylate)‐b‐polyurethane‐b‐poly(D ‐gluconamidoethyl methacrylate) (PGAMA‐b‐PU‐b‐PGAMA) tri‐block copolymers were successfully synthesized via the combination of the step‐growth and copper‐catalyzed atom transfer radical polymerization (ATRP). Dihydroxy polyurethane (HO‐PU‐OH) was synthesized by the step‐growth polymerization of hexamethylene diisocyanate with poly(tetramethylene glycol). PGAMA‐b‐PU‐b‐PGAMA block copolymers were synthesized via copper‐catalyzed ATRP of GAMA in N, N‐dimethyl formamide at 20°C in the presence of 2, 2′‐bipyridyl using Br‐PU‐Br as macroinitiator and characterized by ¹H‐NMR spectroscopy and GPC. The resulting block copolymer forms spherical micelles in water as observed in TEM study, and also supported by ¹H NMR spectroscopy and light scattering. Miceller size increases with increase in hydrophilic PGAMA chain length as revealed by DLS study. The critical micellar concentration values of the resulting block copolymers increased with the increase of the chain length of the PGAMA block. Thermal properties of these block copolymers were studied by thermo‐gravimetric analysis, and differential scanning calorimetric study. Spherical Ag‐nanoparticles were successfully synthesized using these block copolymers as stabilizer. The dimension of Ag nanoparticle was tailored by altering the chain length of the hydrophilic block of the copolymer. A mechanism has been proposed for the formation of stable and regulated Ag nanoparticle using various chain length of hydrophilic PGAMA block of the tri‐block copolymer. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Efficient Whole‐Cell Biocatalytic Synthesis of N‐Acetyl‐D‐neuraminic Acid

N‐Acetyl‐D ‐neuraminic acid (Neu5Ac) was efficiently synthesized from lactate and a mixture of N‐acetyl‐D ‐glucosamine (GlcNAc) and N‐acetyl‐D ‐mannosamine (ManNAc) by whole cells. The biotransformation utilized Escherichia coli cells (Neu5Ac aldolase), Pseudomonas stutzeri cells (lactate oxidase components), GlcNAc/ManNAc and lactate. By this process, 18.32±0.56 g/liter Neu5Ac were obtained from 65.61±2.70 g/liter lactate as an initial substrate input. Neu5Ac (98.4±0.4 % purity, 80.87±0.79 % recovery yield) was purified by anionic exchange chromatography. Our results demonstrate that the reported Neu5Ac biosynthetic process can compare favorably with natural product extraction or chemical synthesis processes.     

D‐Lactic acid production from waste cardboard

The effects caused by alkaline treatment on the susceptibility of waste cardboard to enzymatic hydrolysis have been studied. Optimised conditions leading to extensive saccharification of both cellulose (870 g kg^?1 conversion) and hemicelluloses (845 g kg^?1 conversion) were identified. Samples treated under selected operational conditions were employed for producing D ‐lactic acid by simultaneous saccharification and fermentation (SSF) in media containing cellulases, β‐glucosidase and Lactobacillus coryniformis ssp torquens cells. SSF fed‐batch experiments led to D ‐lactic acid concentrations up to 23.4 g dm^?3 at a product yield of 514 g lactic acid kg^?1 of potential glucose and a volumetric productivity of 0.48 g dm^?3 h^?1. Copyright © 2004 Society of Chemical Industry     

Polymer networks based in (4‐vinylbenzyl)‐N‐methyl‐D‐glucamine supported on microporous polypropylene layers with retention boron capacity

New cellulose porous layers, with capacity to transport and retain boron from aqueous solution, were developed via interpenetrating polymer network (IPNs). These polymer systems were made to assemble mimetic systems of plant root tissue for the study of available boron transport. For that cellulose porous layers supported on polypropylene matrix were used as primary network for the formation of IPN. A vinyl monomer, (4‐vinylbenzyl)‐N‐methyl‐d ‐glucamine (VbNMDG), was synthesized at three concentration levels and cellulose ultrafiltration membranes were modified by in situ polymerization in the inside of the pores. Change of hydrophilicity, percent of secondary network, permeability and retention properties were studied. The formation of IPNs in the inside of the pores decreased the permeabilities of polymer layers. In addition, a decrease of hydrophilicity was seen. A linear increase of boron retention in function of VbNMDG concentrations was observed for the different boron concentrations and a negative effect on retention capability was evidenced for several charge and discharge cycles. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40653.