Synthesis and properties of polyester dendrimers bearing carbazole groups in their periphery

Polyester dendrimers bearing carbazole units at their peripheries were synthesized by attaching 3,5-bis[4-(9-carbazolyl)butoxy]benzoic acid to the peripherical phenoxy groups. The phenoxy-terminated polyester dendrimers were synthesized by hydrogenation of the corresponding benzyloxy-terminated polyester dendrimers. The structure of the synthesized compounds was confirmed with IR, ¹H NMR, MALDITOF MS and GPC. The reaction conditions for attaching 3,5-bis[4-(9-carbazolyl)butoxy]benzoic acid to the peripherical phenoxy groups of polyester dendrimers were studied. Fluorescence spectra studies showed that there exist strong intramolecular interactions in the carbazole dendrimer molecules.     

Synthesis,characterization and polymerization of dendrimers with methacrylic end groups

Dendritic methacrylic crosslinking agents were synthesized by modification of amino functional poly(propyleneimine) dendrimers. On the basis of model reactions, several experimental methods for the introduction of methacrylate end groups were evaluated. In case of the Michael reaction of 2-(acryloyloxy)ethyl methacrylate (1) the amino-end groups of the dendrimers of the second, the fourth or the fifth generation add exclusively onto the acrylic double bonds of 1 forming methacrylic end groups in the modified dendrimers. The quantitative and uniform conversion could be proved by NMR spectroscopy. Analogous dendrimer modifications were carried out with mixtures of 1 and other acrylates. The dendrimeric methacrylates of different generations were polymerized in solution and bulk at 80°C with 2.2′-azoisobutyronitrile as initiator. The polymerization enthalpy of the dendrimeric methacrylates was determined by differential scanning calorimetry and shows that the polymerization of approximately every double bond takes place. The polymerization of methacrylic dendrimers yields crosslinked polymers with glass transition temperatures near or below room temperature.     

Synthesis and characterization of polymers bearing pyrazole groups, 1. Methacrylic derivatives

The synthesis of new methacrylic monomers H₂C? C(CH₃)? COOCH₂? G where G is a pyridine, a pyrazole or a bipyrazole group has been achieved. Their homopolymerization was studied and gave fairly low molecular mass polymers. Their copolymerization with styrene gave copolymers tending to be alternating when the bulkiness of group G increased. Moreover, in the presence of Lewis acids the monomers were complexed. With ZnCl₂, they were complexed through nitrogen atoms and were shown to be inactive in copolymerization. With SnCl₄, they were complexed through the carbonyl group and gave alternating copolymers. The homopolymers exhibited low glass transition temperatures (50–76°C) and moderate thermal stability (decomposition begins at ca. 200–280°C and is complete at 550°C). In the copolymers with styrene the thermal properties showed to be improved.     

Flow in a symmetrically branched tube simulating the aortic bifurcation: The effects of unevenly distributed flow

The effects of unevenly distributed flow were investigated in a symmetrically branched tube with an angle of branching and branch-to-trunk area ratio that were comparable to the human descending aorta. Profiles of velocity were measured at the vertex of the bifurcation with a laser Doppler anemometer during pulsatile flow as well as steady flow. The mean Reynolds numbers were 500, 1000, and 1500. When flow in the branches was equal, reversals were present along the outer wall during the minimal phase of the flow cycle at a Reynolds number of 500. Such reversals were absent at higher Reynolds numbers. When flow in the branches was unequal, reversals occurred only in the branch with the lower flow. Such reversals occurred at all of the Reynolds numbers studied. Pulsatile flow separation, however, did not occur at any Reynolds number when the flow in the branches was equal. Pulsatile flow separation occurred in the partially occluded branch when flow in the branch was ≤8% of the total flow only at Reynolds numbers of 1000 and 1500. A prominent difference between pulsatile and steady flow was that reversals along the outer wall occurred during pulsatile flow at percentages that were prominently higher than the percentage of flow in the branch that produced reversals during steady flow. These observations may be pertinent to understanding the potential of characteristics of flow in the genesis of atherosclerosis in the region of the bifurcation of the aorta. Supported in part by the U.S. Public Health Service-National Heart, Lung and Blood Institute Grant HL23669-02     

Synthesis and cation-sensitive fluorescence of polyelectrolytes bearing crown ether side groups

Polyelectrolytes bearing crowned acetophenone moieties were prepared by radical copolymerization of 4′-acryloylbenzo-18-crown-6

1 System. name of benzo-18-crown-6: 1,2-benzo-1,4,7,10,13,16-hexaoxa-2-octadecene.

and methacrylic acid or lithium 2-acrylamido-2-methyl-1-propanesulfonate. On excitation with 330 nm light the polymers showed fluorescence at 410 nm in a mixed solvent of methanol and water (1:9 v/v) at 30°C. When cations were added, the fluorescence intensity of the polymers decreased in the orders Li⁺ > Na⁺ > Cs⁺ > Rb⁺ > K ⁺ for alkali metal cations, Ca²⁺ > Sr²⁺ > Ba²⁺ for alkaline earth metal cations and C₂H₅NH₂ > CH₃(CH₂)₃NH₂ > C₆H₅CH₂NH₂ for alkylamine hydrochlorides used. The concentration effect for cations in the neighborhood of the polymer-bound crown ether groups by electrostatic and/or hydrophobic binding induced significant complex formation between cations and crown ethers in aqueous solutions, resulting in a decrease of the fluorescence intensity.     

Synthesis of a novel N‐selective ester functionalized chitin derivative and water‐soluble carboxyethylchitin

A novel chitin derivative having a pendant ester function, 2‐N‐(2‐ethoxycarbonylethyl)chitin ( 2 ), was synthesized by a Michael‐type nucleophilic addition of an amino group of partially deacetylated chitin ( 1 ) to ethyl acrylate in phosphate buffer/methanol (5 : 3, v/v) at 40°C. N‐Selective monosubstitution occurred exclusively in the polymer reaction, which was supported by a reaction of methyl 2‐amino‐2‐deoxy‐D ‐glucopyranoside with ethyl acrylate to afford methyl 2‐N‐(2‐ethoxycarbonylethyl)‐2‐amino‐2‐deoxy‐D ‐glucopyranoside. The degrees of substitution (DSs) of 2 were determined by ¹H NMR spectroscopy. T₁ analysis of 2 was carried out in order to clarify differences of signal intensities of the pendant ester protons and the pyranose ring protons. The result of the T₁ measurement suggested a relatively restricted molecular motion of the chitin backbone in comparison with the flexible pendant ethyl ester groups. Furthermore, 2‐N‐(2‐carboxyethyl)chitin sodium salt ( 3 ) was synthesized from ethyl acrylate and 1 by the Michael addition followed by hydrolysis in 0.1 N NaOH aq. at 40°C. The DSs of 3 were varied from 0.26 to 0.88, which were almost controlled by the reaction period of the Michael reaction from 6 to 168 h. 3 showed good solubility in water. Viscosity measured on a cone‐plate viscometer for the 1.0 wt.‐% aqueous solution of 3 (DS, 0.26) was 0.074 Pas·sec.     

Polymeric protecting groups, 5. Polymerizable urea compounds with 2-methylpropyloxycarbonyl function as a modified tert-butoxycarbonyl-type amino-protecting group

1-[2-(4-chloroanilinocarbonyloxy)-2-methylpropyl]-3-methacryloylurea ( 4 ) was prepared by addition of 1-(2-hydroxy-2-methylpropyl)-3-methacryloylurea ( 3 ) to 4-chlorophenyl isocyanate as a model compound. The new monomer 4 acts as a modified tert-butoxycarbonyl (BOC)-type amino-protecting group which can be homopolymerized and copolymerized with methyl methacrylate (MMA) upon radical initiation. The kinetics of the deprotection of the aromatic amine under acidic conditions which leads to the formation of 2-methacryloylamino-5,5-dimethyl-Δ²-1,3-oxazoline ( 7 ) was followed by means of ¹H NMR spectroscopy.     

Polymerizable mesoionic 4,6-dioxo-1,3-diazines, 1. Synthesis and photochemical behavior of polystyrenes with mesoionic 4,6-dioxo-1,3-diazines as pendant groups

Mesoionic 5-alkyl-4,6-dioxo-1,3-diphenyl-2-(3-vinylbenzylthio)-1,3-diazine ( 6 ) was prepared by condensation of alkylmalonic acid ( 5 ) with 1,3-diphenyl-2-(3-vinylbenzyl)isothiourea ( 4 ) by use of dicyclohexylcarbodiimide (DCC). Homopolymerization of 6 led to new polystyrene derivatives ( 7 ) with mesoionic 4,6-dioxo-1,3-diazines as pendant groups. UV irradiation of 7 yielded polystyrene derivatives with bis(β-lactam) moieties as pendant groups ( 8 ). The change of some physical properties during the irradiation is discussed. 5-Heptyl-4,6-dioxo-1,3-diphenyl-2-(3-methylbenzylthio)-1,3-diazine ( 11 ) and 4-heptyl-1-(3-methylbenzylthio)-3,5-dioxo-2,6-diphenyl-2,6-diazabicyclo[2.2.0]hexane ( 12 ) as low-molecular-weight model compounds were synthesized for structural analysis.     

Radically initiated copolymers of styrene with 4-vinylbenzylamine and its trifluoroacetamide derivative, 2. Preparation of latex particles bearing amino groups

Polystyrene(PS)-based latex particles bearing amino groups have been prepared using a two-step process consisting of seeded copolymerization of a monomer mixture with styrene (S) and either 4-vinylbenzylamine (VBA) or its trifluoroacetamide derivative (VBAF) in the presence of monodisperse PS latex. Poor colloidal properties and bad chemical stability were found in the case of latexes obtained with VBA. Better results were obtained with VBAF, but conversion was not completed. Surface characterization of the final latexes by ¹H NMR, XPS and colorimetric titration offer some insight into the location of the VBAF monomer units within the particles.     

Synthesis of polystyrene-poly(tert-butyl acrylate) diblock copolymers bearing fluorescent groups at the junctions

AB-type diblock copolymers composed of polystyrene as the A block and poly(tert-butyl acrylate) as the B block were synthesized by sequential anionic polymerization. 1-(2-Anthryl)-1-phenylethylene, a new fluorescent monomer, and 1-(9-phenanthryl)-1-phenylethylene were used to introduce fluorescent moieties at the block junctions. Ultraviolet (UV) spectroscopy and gelpermeation chromatography (GPC) analyses were used to characterize the prepared copolymers.     

Synthesis of a diphenylethylene derivative carrying aromatic tertiary amine groups and its use in chain end functionalization of alkyllithium-initiated polymerizations

1,1-Bis[(4-dimethylamino)phenyl]ethylene was successfully synthesized through the ‘Wittigtype’ reaction of 4,4′-bis(dimethylamino)benzophenone with the ‘Tebbe’ reagent. The methylenation yields were over 80 wt.-% on the basis of the initial amount of benzophenone derivative used. Terminally functionalized polymers having aromatic tertiary amine groups at one end or at both ends were prepared by the crossover reactions of n-butyllithium (n-BuLi), poly(styryl)lithium (PSLi), and poly(isoprenyl)lithium (PILi) with the diphenylethylene analogue. The functionalization yields were over 87 mol.-% based on the results of ¹H NMR spectroscopic analysis. The number-average molecular weights of the polymers based on the ratio [gram of monomer]/[mole of initiator] are in good accordance with those observed from size exclusion chromatographic and ¹H NMR spectroscopic analysis (3,0 × 10³ ∼ 7,5 × 10³ g/mol).     

Synthesis of chitin derivatives having peptide side groups by the water‐soluble active ester method

Novel chitin derivatives having pendant monopeptide and tripeptide units, i. e., N‐(N′‐acetylglycyl)chitin ( 3 a ) and N‐(N′‐acetylglycylglycylglycyl)chitin ( 3 b ), were synthesized from 50% deacetylated chitin by the water‐soluble active ester method in a homogeneous system at 27–50°C. Without protection of hydroxyl groups, amino groups of the partially deacetylated chitin were selectively acylated by using esters of the corresponding N‐acetylated amino acids with (4‐hydroxyphenyl)dimethylsulfonium methyl sulfate in water. The degree of substitution of the D ‐glucosamine moiety of chitin is changed with the feed mole ratio of the active ester reagent to amino groups. As a new type of amphiphilic polysaccharides of lipid/peptide/polysaccharide conjugates, N‐(N′‐lauroylglycyl)chitin ( 3 c ) and N‐(N′‐lauroylsarcosyl)chitin ( 3 d ) were synthesized in the corresponding way.     

Synthesis of a reactive purine derivative for use as a hapten

Chemically stable haptens such as purines present difficulties when conjugates are required for immunoassay development. This short communication describes the strategy adopted when such an immunogen was required to elicit anti‐hypoxanthine antibodies.     

Water-soluble polymers bearing biologically active residues, 1. Synthesis and characterization of poly(ether-ester)s bearing hydroxyl side groups and their derivatization with 1-naphthylacetic acid

The synthesis of low-molecular-weight poly(ether-ester)s bearing hydroxyl side groups by poly-condensation, in 1-methyl-2-pyrrolidone at 105–110°C, of the potassium salts of racemic malic and (R,R)-tartaric acids and α-(2-bromoethyl)-ω-bromopoly(oxyethylene)s of different molecular weights is described. The polymers were characterized by GPC and ¹H and ¹³C NMR. The fixation of 1-naphthylacetic acid, a plant growth regulating agent, was successfully achieved in the case of poly(ether-ester)s deriving from tartaric acid, by carrying out the esterification reaction at room temperature in the presence of N,N′-dicyclohexylcarbodiimide and 4-dimethylaminopyridine.     

Biofunctionalization of silicone polymers using poly(amidoamine) dendrimers and a mannose derivative for prolonged interference against pathogen colonization

Despite numerous preventive strategies on bacterial adhesion, pathogenic biofilm formation remained the major cause of medical device-related infections. Bacterial interference is a promising strategy that uses pre-established biofilms of benign bacteria to serve as live, protective coating against pathogen colonization. However, the application of this strategy to silicone urinary catheters was hampered by low adherence of benign bacteria onto silicone materials. In this work, we present a general method for biofunctionalization of silicone (PDMS) as one of the most widely used materials for biomedical devices. We used mild CO(2) plasma to activate PDMS surface followed by simple attachment of generation 5 (G5) poly(amidoamine) (PAMAM) dendrimers to generate an amino-terminated surface that were maintained even after storage in PBS buffer for 36 days. We then covalently attach a carboxy-terminated mannose derivative to the modified PDMS to promote the adherence of benign Escherichia coli 83972 expressing mannose-binding type 1 fimbriae. We demonstrated that dense, stable biofilms of E. coli 83972 could be established within 48 h on the mannose-coated PDMS. Significantly, this benign biofilm reduced the adherence of the uropathogenic Enterococcus faecalis by 104-fold after 72 h, while the benign bacteria on the unmodified substrate by only 5.5-fold.     

Synthesis of branched antisense oligonucleotides having multiple specificities. Treatment of hormone insensitive prostate cancer

Antisense oligonucleotides (oligos) directed against transforming growth factor-alpha (TGF-alpha) and its binding site, the epidermal growth factor receptor (EGFR), have demonstrated in vitro and in vivo efficacy against both the PC-3 and LNCaP prostate tumor models. In an attempt to increase the efficiency of these oligos a new type of antisense compound called a bispecific oligo has been evaluated in vitro both alone and in combination with traditional chemotherapeutic agents. These bispecifics, which were first proposed in this journal in 2004, include binding sites for both TGF-alpha and EGFR along the same stretch of complementary DNA. Such bispecifics are able to deliver essentially two antisense activities in an equal molar ratio and can be directed against mRNA encoding proteins of different biochemical pathways. The first bispecifics were developed against two proteins regulating a single autocrine loop. Subsequent bispecifics have been developed which target both EGFR and the apoptosis regulating protein bcl-2. Bispecific activity of a single linear sequence oligo has already been shown to have efficacy. To further develop this multispecific approach, we now propose a branched antisense compound, again, having multiple binding site activities (to complementary sequenced mRNA). Active oligos would be attached to a fat soluble backbone which might enhance targeting and also intracellular entry, release and activity. Such a structure would also permit the customization of these branched forms to include oligos targeting specific proteins related to the growth of various tumor types. Problems associated with the development of antisense oligos have included both membrane solubility and specific targeting. By designing this branched form of antisense structure, multiple activities can be retained (added), solubility improved and delivery enhanced. Such a new formulation would include several antisense oligos covalently bound to and branching off from a lipid-like backbone. An elongated hydrocarbon chain would increase fat solubility and would permit oligo incorporation into nanoparticles or liposome derived delivery vehicles. Specific delivery of oligos could also be enhanced by the tendency of these nanoparticle or liposomal microbubbles to be disrupted under the influence of ultrasonic waves beamed at the targeted tissue.     

Water-soluble polymers bearing biologically active residues, 3. Hydrolysis of polyethers and poly(ether-ester)s bearing 1-naphthylacetyl groups

The hydrolysis of esters of naphthylacetic acid (NAA) and poly(ethylene glycol)s (PEG-NAAs) or poly[oxytartaroyloxypoly(oxyethylene)]s (PTEG-NAAs) was studied at pHs 9.2, 7,1 and 4, 5. The hydrolysis of complexes of PEG-NAA with poly(methacrylic acid) (PMA) was also studied. UV spectroscopy and GPC were used to follow the release of NAA and the changes in the molecular weight of the polymers. The hydrolysis of PEG-NAAs follows a first-order kinetics. The rate constants of hydrolysis of PEG₃₀₀₀-NAA are higher than those of PEG₄₀₀₀-NAA, and this is attributed to a shielding effect of the polymer chain. The hydrolysis of PTEG-NAA proceeds with release of NAA from the end-groups and the pendent groups as well as with scission of the main-chain ester groups. It is proposed that the very slow hydrolysis of complexes of PEG-NAA with PMA is due to the localization of naphthylacetyl groups in the hydrophobic domains of the polycomplexes.     

Saccharide polymers, 3. Synthesis and polymerization of a 5,6‐unsaturated fructofuranoid derivative

A new exo‐fructofuranoid monomer 5 was synthesized through a four‐step reaction. This unsaturated sugar monomer has been successfully tested in radical polymerization. Homo‐ and copolymerizations were carried out in solution under various conditions. The corresponding saccharide polymers were isolated as white powder and well characterized. Polymer compositions were determined by elemental analysis (C, H, N) and ¹H and ¹³C NMR. Polymerization parameters were determined for the binary system 1,2,3,4‐tetra‐O‐benzoyl‐6‐deoxy‐α‐D ‐threo‐5‐eno‐hexofuranose‐2‐uloside ( 5 )/MA giving the reactivity ratios r₁ = 0.47 for 5 and r₂ = 1.13 for MA. The thermal behaviour of saccharide polymers was investigated showing a linear relationship between the glass transition temperature (T_g) of the saccharide polymers and the sugar content. The saccharide polymers also showed optical activity and exhibit negative optical rotation. Both T_g and the specific optical rotations ([α]²⁰_D) increase with increasing sugar content.