Mechanical stabilization of molecular conformation by entrapping in a polymer matrix

5-Methacryloyl- and 5-isobutyrylaminosalicylaldehydes ( 5a and 5b , respectively) and diastereomeric complexes of their Schiff bases with amino acids and Co(III): potassium Λ- and Δ-bis-[N-5-methacryloylaminosalicylidene-(S)-valinato]cobaltate(III) ( 6a , b ), potassium Λ- and Δ-bis[N-5-isobutyrylaminosalicylidene-(S)-norvalinato]cobaltate(III) ( 7a, b ), potassium Λ- and Δ-bis[N-5-methacryloylaminosalicylidene-(S)-norvalinato]cobaltate(III) ( 8a, b ), have been synthesized. Copolymerization of 6–7a, b with acrylamide and N,N′-methylenebis(acrylamide) leads to the formation of transparent hydrophilic gels in which the amino acid fragments preserve their ability of exchanging α-hydrogen for deuterium in an alkaline medium. Comparison of the behaviour of polymer complexes ?- 7a and ?- 7b in the process of base-catalyzed epimerization with their monomer analogues 8a and 8b shows that their stereoselectivity substantially changes when one goes from 8a to ?- 7a . Such an effect may be explained by stabilization of the initial conformation of the complex molecule by the polymer matrix formed around the complex acting as a template.     

Effect of adjacent functional groups on the electron-donor-acceptor complex formation of diethyl 2,2-bis(dinitrobenzyl)malonates and 2,2-bis(4-dimethylaminobenzyl)malonate

In order to study the effect of adjacent functional groups on electron-donor acceptor (EDA) complex formation, the following donor or acceptor compounds were synthesized: diethyl 2-(2,4-dinitrobenzyl)malonate ( 13 ), diethyl 2,2-bis(2,4-dinitrobenzyl)malonate ( 14 ), diethyl 2-(3,5-dinitrobenzyl)malonate ( 5 ), diethyl 2,2-bis(3,5-dinitrobenzyl)malonate ( 6 ), diethyl 2-(4-dimethylaminobenzyl)malonate ( 10 ), diethyl 2,2-bis(4-dimethylaminobenzyl)malonate ( 11 ). The acceptor compounds 5, 6, 13 , and 14 were complexed with N,N-dimethyl-4-dimethylaminoaniline ( 1 ) as donor, and the donor compounds 10 and 11 , with 1,3,5-trinitrobenzene ( 2 ) as acceptor. The wave length of the absorption maximum (λ_max), the association constant (K_CT), the enthalpy (δH), and entropy (δS) of these EDA complexes were determined. It was found that λ_max of complexes 6–1 and 11–2 show a bathochromic shift compared with complexes 5–1 and 10–2 , and the values of K_CT, ?δH, and ?δS are higher. The value of λ_max for complex 14–1 is not different from that of complex 13–1 , and the values of K_CT, ?δH, and ?δS are lower. It was concluded that the stability of the EDA complexes of the 2,2-dibenzylmalonate derivatives 6, 11 , and 14 , is influenced by π-electron interaction between the adjacent two benzene rings.     

Memory of a polymeric matrix,stabilizing the initial conformation of potassium bis[N-(5-methacryloylamino)-salicylidene-(S)-norvalinato]-cobaltate(III) in the deuterium exchange

Copolymerization of potassium Λ- and Δ-bis[N-(5-methacryloylamino)salicylidene-(S)-norvalinato]-cobaltate(III) ( 1 and 2 ) with acrylamide and N,N′-methylenediacrylamide gives crosslinked gels. The behaviour of the amino acid moiety in the gel obtained from the isomer with the Δ(S,S) configuration does not differ from that of the monomeric model compound 4. The Λ(S,S) isomer gives gels, in which a part of the complex proves to be attached by both phenyl moieties to one polymeric chain forming a macrocycle. Deuterium exchange in such complexes proceeds with full retention of the configuration of the amino acid.     

Asymmetric sorbents based on mono- and diamines and resolution of racemates by ligand-exchange chromatography

The asymmetric sorbents A, B, C, and D were prepared by interaction of a chloromethylated styrene copolymer of the isoporous macronet type (5,5% of crosslinks) with the chiral amines (S)-1-phenylethylamine, (R)-1,2-propanediamine, and their derivatives. Resins A and B , based on 1-phenylethylamine, do not sorb Cu(II) ions, whereas resins C and D , based on 1,2-propanediamine saturated with Cu(II) ions, were successfully used for ligand-exchange chromatography of amino acids, showing higher affinity to aminodicarboxylic acids than to diaminocarboxylic acids. Sorbent D displays an enantioselectivity of α ≥ 1,5 towards amino acids like Ala, Abu, Ser, or Lys and provides quantitative resolution of enantiomers of some other amino acids. L -amino acids are retained longer by resins C and D than D-isomers.     

Metal complexes of alkyl substituted poly(vinylpyridine 1-oxide)s and of poly (dimethylaminostyrene N-oxide)s

Three alkyl derivatives ( 3, 4 , and 5 ) of poly[1-(N-oxo-pyridyl)ethylene]s (poly(vinylpyridine 1-oxide)s) give complexes with some or all chlorides of copper (II), zinc, mercury(II), iron(III), and cobalt(II), in which all the N-oxide groups are coordinated with metal, the mole ratio NO/metal being 2:1. The three poly[(N-oxo-dimethylamino)phenylethylene]s (poly(dimethylaminostyrene N-oxide)s) ( 6, 7 , and 8 ) give complexes with copper(II), mercury(II), and iron(III) chlorides but, even when an excess of metal chloride is available, some N-oxide groups do not coordinate with metal as shown by IR absorption data. The degree of coordination is 0,5 for complexes of 6 , but it is 0,4 for the complexes of 7 and 0,33 for the complexes of 8 .     

Coordination polymers of N,N′-bis(8-hydroxy-5-quinolinyl)-terephthalamide

Fe(II), Co(II), Ni(II), Cu(II) and Zn(II) complexes of the bisbidentate ligand N,N′-bis(8-hydroxy-5-quinolinyl)terephthalamide ( 1 ) were synthesized. All the metal complexes are characterized by elemental analyses, infrared spectra, electronic reflectance spectra, magnetic susceptibility measurements and thermogravimetry. All the complexes showed a polymeric nature with a octahedral stereochemistry at the coordinated metal atom. The fungicidal screening of the coordination polymers showed them to be antifungal against Penicillium islandicum, Rizopus nigricans and Botrydiplodia theobromae.     

Polypeptides containing adenine and uracil residues

Amino acids containing uracil, adenine and imidazole residues were prepared and polymerized by reacting with phosgene in ethylene carbonate. The polymers did not have a simple polypeptidic structure but were soluble in aqueous dimethylformamide and interacted with complementary polynucleotides. Alternative polymerization of amino acids by N,N′-carbonyldiimidazole in aqueous neutral buffers proceeded with very low conversion but pure polypeptides resulted from the reaction. The following amino acids were prepared: β-adenin-9-yl-α-alanine ( 1a ), N-methyl-β-(adenin-9-yl)-α-alanine ( 1b ), β-(uracil-1-yl)-α-alanine, ( 2a ), N-methyl-β-(uracil-1-yl)-α-alanine ( 2b ), β-(5,6-trimethyleneuracil-1-yl)-α-alanine ( 3 ), and β-(imidazol-1-yl)-α-alanine.     

Effect of N,N,N′,N′-tetramethylethylenediamine on the reaction parameters of Ziegler-Natta macromolecular complexes in the polymerization of ethylene

Soluble complexes of ω-lithiumbutenylpoly(styrene-co-butadiene) (≈ 100: ≈ 3 DP) with TiCl₄ were used in conjunction with N,N,N′,N′-tetramethylethylenediamine (TMEDA), to initiate the polymerization of ethylene. The activity of such a system was measured as a function of the number of amino groups (N) per active center (A. C.) ([N]/[A. C.]). From measurements of the amount of polystyrene-block-polyethylene produced and from kinetic studies of the polymerization of ethylene, the influence of TMEDA on both the efficiency of the system and the reactivity of the active species was studied. The depressor effect of the diamine on the reaction parameters, controlling the polymerization of ethylene, was connected with the proposed structure of the active sites. The role of the Lewis base was discussed by assuming a reversible blockage of a vacant coordination site at the titanium throughout the complexation of the electrophilic “host sites” of the polymer [TiCl₂, TiCl₃, 3 LiCl] complexes.     

Electrochemical polymerization of derivatives from N-methylpyrrole and thiophene to heteroarylenevinylene polymers

The heteroaryl- and heteroarylenevinylene compounds 1, 2, 3 , and 4 were investigated by means of cyclic voltammetry and submitted to oxidative electropolymerization under galvanostatic conditions; the products obtained were further characterized by means of elemental analysis, optical absorption spectroscopy and conductivity measurements. (E)-1,2-bis(N-methyl-2-pyrrolyl)ethylene ( 1 ), 2,5-bis[(E)-2-(N-methyl-2-pyrrolyl)vinyl]thiophene ( 2 ) and N-methyl2,5-bis[(E)-2-(N-methyl-2-pyrrolyl)vinyl]pyrrole ( 3 ) gave brittle to spongy films on electropolymerization with perchlorate as the counterion balancing the positive charge on the polymer backbone units. The d. c. conductivity of all three polymers (as perchlorates) was of the order of 10^?3 Ω^?1·cm^?1. N-methyl-2,5-bis[(E)-2-(2-thienyl)vinyl]pyrrole ( 4 ) did not give a solid polymer.     

Growth mechanism of crystals of glycine/S-methyl-L-cysteine copolymer in the course of polymerization

In order to examine the growth mechanism of copolymer crystals formed during polymerization, the heterogeneous copolymerization of glycine N-carboxy anhydride (2,5-dioxo-1-oxa-3-azacyclopentane) and S-methyl-L -cysteine N-carboxy anhydride (4-methylthiomethyl-2,5-dioxo-1-oxa-3-azacyclopentane) was studied in acetonitrile. In all the polymerization systems, the crystal growth occurs through formation of the cross-β-type structure. The high conversion in the glycine-rich systems is accounted for by the widening of the cross-section of the β-chain in the backbone crystal, due to the introduction of S-methyl-L -cysteine residues into the polyglycine chain. On the other hand, the narrowing of the cross-sectional area per chain in the skeleton crystals of the oligomer gave rise to the lowering of the conversion in the S-methyl-L -cysteine-rich systems. This shows the importance of the effect of the cross-sectional area of the oligomer chain (of the β structure) in the crystal formed in the begining relative to that of the growing (α-helical) chain. The glycine residue seems to be incorporated into the crystalline lattice of the S-methyl-L -cysteine and vice versa.     

Synthesis of polymers with primary amino end groups, 2. Synthesis of polyisoprene with primary amino end groups and poly(isoprene-b-γ-benzyl-L-glutamate)s

Primary amine terminated polyisoprene 2 was produced by reaction of anionic living polyisoprene with one of the following protected aminating reagents: N-(benzylidene)trimethylsilylamine ( 1a ). N-(1-phenylpentylidene)trimethylsilylamine ( 1b ), N-benzylidenebenzenesulfeneamide ( 1c ), or N,N-bis(trimethylsilyl)-2-bromoethylamine ( 3 ). Especially with 1a , the terminal amino group was quantitatively introduced at the end of the polymer chain. 2 was found to initiate the polymerization of the N-carboxy anhydride of γ-benzyl-L -glutamate 5 to afford poly(isoprene-b-γ-benzyl-L -glutamate) ( 6 ).     

Chelation properties of polymer complexes of poly(acrylic acid) with poly(acrylamide), and poly(acrylic acid) with poly(N,N-dimethylacrylamide)

The metal-complexing properties of intermolecular complexes of poly(acrylic acid) with poly(acrylamide), and poly(acrylic acid) with poly(N,N-dimethylacrylamide) were studied by means of the liquid-phase polymer based retention (LPR) technique. The metal ion retention ability at pH 5 for 400 μg of Cu(II), Cd(II), Co(II), Cr(III), Hg(II), Ni(II), Pb(II), and Zn(II) was investigated due to their environmental and analytical interest in the presence of 1.1 M of carboxylic acid units and variable amounts of amide groups. The retention profiles of the intermolecular complexes were compared with those of the correspondent homopolymers and copolymers. The retention capacity of poly(acrylic acid) is 100% for all metal ions except for Co(II), Ni(II), and Zn(II) whose values were about 90%, while poly(acrylamide) does not retain any of the metal ion studied. The presence of poly(acrylamide) decreases the retention capacity down to 60% for Co(II) and Ni(II) and to 70% for Zn(II). The decrease on the retention values is dependent on the polymer ratio. A smaller effect is observed by the addition of poly(N,N-dimethylacrylamide) which also decreases the retention capacity down to 80% for Co(II) and Ni(II) for a ratio poly(acrylic acid)/poly(N,N-dimethylacrylamide) = 1/2. The metal ion binding behavior of the interpolymer complexes is very close to that of the copolymers.     

Biomimetic approach to the design of a pyridoxal enzyme model, 1. Hydrophilic polyacrylamide gel with stereochemically defined arrangement of salicylaldehyde and lysine fragments

A polymeric gel in which salicylaldehyde and lysine moieties are capable of forming an “internal” aldimine at pH > 6,0 has been prepared by copolymerization of N^α-5-methacryloylaminosalicylidene-N^ε-methacryloyl-(S)-lysinatocopper (II) ( 1a ) with acrylamide and N,N'-methylenebisacrylamide in water with subsequent removal of the copper ions by 0,1 M HCl or the disodium salt of EDTA. The equilibrium formation constants of the “internal” aldimine are ca. 30 times (at pH 7,1) and ca. 100 times (at pH 9,2) higher than the equilibrium constants of the model reaction of Schiff base formation from 5-isobutyrylaminosalicylaldehyde ( 2 ) and N^t-isobutyryl-(S)-lysine ( 3 ). The α-amino group of the lysine residue in the gel acts as a nucleophilic catalyst in the reaction of the salicylaldehyde moiety of the gel with semicarbazide. The reaction proceeds 5,3 times faster in the gel than in a model polymeric system which does not contain lysine moieties.     

Protection and polymerization of functional monomers, 14. Anionic living polymerization of 4-[N,N-bis(trimethylsilyl)-aminomethyl]styrene and 4-{2-[N,N-bis(trimethylsilyl)amino]ethyl}styrene

Anionic polymerization of 4-[N,N-bis(trimethylsilyl)aminomethyl]styrene ( 1 ) and 4-{2-[N,N-bis(trimethylsilyl)amino]ethyl}styrene ( 2 ) were carried out at ?78°C in tetrahydrofuran (THF)/pentane mixtures with butyllithium, oligo(α-methylstyryl)lithium, oligo(α-methylstyryl)potassium, and cumylpotassium. Polymerizations of 1 and 2 proceed without chain transfer and termination reactions to give stable “living polymers” when butyllithium or oligo(α-methylstyryl)lithium are used as initiator. The resulting polymers have predictable molecular weights and narrow molecular weight distributions (ratio of weight- to number-average molecular weights, M?_w/M?_n = 1,04–1,14). Under mild acidic conditions (pH 3–5 in THF/water), cleavage of the N? Si bonds in the polymers is completely achieved to give well-defined poly(4-aminomethyl)styrene and poly[4-(2-aminoethyl)styrene]. The triblock copolymers of polystyrene-block-poly( 1 )-block-polystyrene and polystyrene-block-poly( 2 )-block-polystyrene are readily prepared in quantitative yields by sequential polymerization of styrene with living poly( 1 ) or living poly( 2 ).     

Synthesis of mainly linear poly(dichlorophenylene oxide)s by thermal polymerization in solution

Thermal decomposition of bis(4-bromo-2,6-dichlorophenoxo)-(N,N,N',N'-tetramethylethy-lenediamiene)copper(II) complex in toluene, bis(4-bromo-2,6-dichlorophenoxo)(N,N-dimethyl-formamide)copper(II) complex in N,N-dimethylformamide and bis(4-bromo-2,6-dichlorophenoxo)(dimethyl sulfoxide)copper(II) complex in dimethyl sulfoxide was achieved at 70°C. 4-Bromo-2,6-dichlorophenol derivatives prefer 1,4-addition to 1,2-addition, leading to highly linear polymers irrespective of the substituted ligands. The complexes were characterized by IR spectroscopy and C, H, N elemental analysis. The characterization of the synthesized polymers were achieved by ¹H NMR, ¹³C NMR and IR spectroscopy. The highest polymer yield was obtained from the decomposition of bis(4-bromo-2,6-dichlorophenoxo)(N,N,N',N'-tetramethyl-ethylenediamine)copper(II) complex.     

Enantioselektive Trifluoracetylierung mit Hilfe chiraler Polyamide

(S)-Poly(2-aminobutyric acid) ( 1 ) [(S)-poly(imino-1-methyl-3-oxotrimethylene)] was transformed into its N-trifluoroacetyl derivative 4 . The IR spectra and the circular dichroism of both substances were compared. In addition, (S)-poly[N-(1-phenylethyl)acrylamide] ( 2 ) ((S)-poly-[1-(1-phenylethylaminocarbonyl)ethylene]) was trifluoroacetylated leading to polymer 5. 4 was found to react as trifluoroacetylating agent with L -1-phenylethylamine (L - 3 ) twice as fast as it reacts with D - 3 . Accordingly, the reaction of 4 with D ,L - 3 leads preferentially to the L -form of N-(1-phenylethyl)trifluoroacetamide with optical yields up to 6%. The reaction of 5 with D ,L - 3 affords the D -form of N-(1-phenylethyl)trifluorcacetamide with optical yields up to 13%.     

Coordination polymers of 1,2,5,8-tetrahydroxyanthraquinone

From analytical studies, infrared and reflectance spectra, magnetic and thermogravimetric measurements of Cu(II), Ni(II), Co(II), Mn(II), Fe(II), and UO₂(VI) complexes of 1,2,5,8-tetrahydroxyanthraquinone, it was concluded that the complexes are polymeric coordination complexes with octahedral geometry. These were synthesized by refluxing an equimolar mixture of the ligand and hydrated metal acetates in N,N-dimethylformamide at 140°C. Elemental analyses indicated a ligand: metal ratio of 1 : 1 and the association of water molecules with the central metal. The decreasing order of thermal stability of the complexes is: Mn(360°C)>Fe(340°C) ≈? Co(340°C)>Ni(320°C)>Cu(300°C).     

Potential antiradiation polymers, 1. Isothiouronium salts,thiosulphates and dithiocarbamates

Polymers were synthesized that contain isothiouronium, thiosulphate or dithiocarbamate residues, which occur in known radioprotectors of low molecular weight. By copolymerizing a monomer containing the radioprotective residue with 1-vinyl-2-pyrrolidone or acrylic acid, polymers were formed that were soluble in water. Polymers containing isothiouronium residues were obtained directly from an ethylenic isothiouronium salt and 1-vinyl-2-pyrrolidone, and by the reaction of an intermediate halogen-containing polymer with thiourea. Polymers containing thiosulphate or dithiocarbamate residues were obtained by copolymerization of the appropriate monomer with 1-vinyl-2-pyrrolidone. Molecular weights (GPC), determined for three of the copolymers, did not exceed 12000. In preliminary tests in mice, poly[S-(2-acryloylaminoethyl)isothiouronium chlorideco-1-vinyl-2-pyrrolidone] ( 4b ) and poly(N,N-diethyl S-vinyldithiocarbamate-co-acrylic acid) ( 6 ) showed some radioprotective activity.     

Immobilisation du complexe de nickel de l'histidine L(+) sur des supports macromoléculaires hydrophiles

N-(4-vinylbenzyl)-L -histidine ( 5 ) and the corresponding methyl ester were synthesized by reacting L -histidine or L -histidine methyl ester with 4-formylstyrene. N-(4-vinylbenzyl)-L -histidine methyl ester was radically copolymerized with various amounts of 2-hydroxyethyl methacrylate and ethylene dimethacrylate, leading to resins of different degrees of hydrophilicity and crosslinking. After saponification of the histidine ester groups, the resins were chelated with Ni²⁺ salt in order to be used as polymeric catalysts in enantioselective ester hydrolysis reactions.     

Darstellung und Derivatisierung von linearem Polyvinylamin zur selektiven Komplexbildung in homogener Phase

Poly(1-aminoethylene) (polyvinylamine) ( 4 ) was prepared by hydrazinolysis of poly(1-succinimidoethylene) ( 2 ) [poly(N-vinylsuccinimide)]. The water-soluble polymer 4 , with more than 95% of primary amino groups, was used as basic material for the synthesis of macromolecular complex forming reagents. By the reaction of poly(1-ammonioethylene chloride) ( 3 ) [poly(vinylamine hydrochloride)] with 2-pyridinecarbaldehyde a complex forming polymer 5 was obtained, which is highly selective for iron. Poly{1-[bis(carboxymethyl)amino]ethylene} ( 6 ) from 4 and chloroacetic acid is a reagent for copper, whereas poly[1-(3-methylthioureido)-ethylene] ( 7 ) from 4 and N-methylisothiocyanate shows a good selectivity for mercury. The ultrafiltration technique allows a continuous procedure for the separation of the polymer complexes. The formation and stability of the prepared complexes of 4 and its derivatives 5, 6 , and 7 in homogeneous phase are investigated and discussed.