Synthesis and Characterization of Anionic Poly(cyclopentadienylene vinylene) and Its Use in Conductive Hydrogels.

The use of π-conjugated polymers (CPs) in conductive hydrogels remains challenging due to the water-insoluble nature of most CPs. Conjugated polyelectrolytes (CPEs) are promising alternatives because they have tunable electronic properties and high water-solubility, but they are often difficult to synthesize and thus have not been widely adopted. Herein, we report the synthesis of an anionic poly(cyclopentadienylene vinylene) (aPCPV) from an insulating precursor under mild conditions and in high yield. Functionalized aPCPV is a highly water-soluble CPE that exhibits low cytotoxicity, and we found that doping hydrogels with aPCPV imparts conductivity. We also anticipate that this synthetic strategy, due to its ease and high efficiency, will be widely used to create families of not-yet-explored π-conjugated vinylene polymers.

Norbornadienes: Robust and Scalable Building Blocks for Cascade "Click" Coupling of High Molecular Weight Polymers.

Herein, we report the development of a scalable and synthetically robust building block based on norbornadiene (NBD) that can be broadly incorporated into a variety of macromolecular architectures using traditional living polymerization techniques. By taking advantage of a selective and rapid deprotection with tetrazine, highly reactive "masked" cyclopentadiene (Cp) functionalities can be introduced into synthetic polymers as chain-end groups in a quantitative and efficient manner. The orthogonality of this platform further enables a cascade "click" process where the "unmasked" Cp can rapidly react with dienophiles, such as maleimides, through a conventional Diels-Alder reaction. Coupling proceeds with quantitative conversions allowing high molecular weight star and dendritic block copolymers to be prepared in a single step under ambient conditions.

Cationic Cyclopentadienyliron Complex as a Novel and Successful Nucleating Agent on the Crystallization Behavior of the Biodegradable PHB Polymer.

Cationic cyclopentadienyliron (CpFe⁺) is one of the most fruitful organometallic moieties that has been utilized to mediate the facile synthesis of a massive number of macromolecules. However, the ability of this compound to function as a nucleating agent to improve other macromolecule properties has not been explored. This report scrutinizes the influence of the cationic complex as a novel nucleating agent on the spherulitic morphology, crystal structure, and isothermal and non-isothermal crystallization behavior of the Poly(3-hydroxybutyrate) (PHB) bacterial origin. The incorporation of the CpFe⁺ into the PHB materials caused a significant increase in its spherulitic numbers with a remarkable reduction in the spherulitic sizes. Unlike other nucleating agents, the SEM imageries exhibited a good dispersion without forming agglomerates of the CpFe⁺ moieties in the PHB matrix. Moreover, according to the FTIR analysis, the cationic organoiron complex has a strong interaction with the PHB polymeric chains via the coordination with its ester carbonyl. Yet, the XRD results revealed that this incorporation had no significant effect on the PHB crystalline structure. Though the CpFe⁺ had no effect on the polymer's crystal structure, it accelerated outstandingly the melt crystallization of the PHB. Meanwhile, the crystallization half-times (t0.5) of the PHB decreased dramatically with the addition of the CpFe⁺. The isothermal and non-isothermal crystallization processes were successfully described using the Avrami model and a modified Avrami model, as well as a combination of the Avrami and Ozawa methods. Finally, the effective activation energy of the PHB/CpFe⁺ nanocomposites was much lower than those of their pure counterparts, which supported the heterogeneous nucleation mechanism with the organometallic moieties, indicating that the CpFe⁺ is a superior nucleating agent for this class of polymer.

Computationally Guided Catalyst Design in the Type I Dynamic Kinetic Asymmetric Pauson-Khand Reaction of Allenyl Acetates.

The Rh(I)-catalyzed allenic Pauson-Khand reaction (APKR) is an efficient, redox-neutral method of synthesizing α-acyloxy cyclopentenones. An enantioselective APKR could provide access to chiral, nonracemic α-acyloxy and α-hydroxy cyclopentenones and their corresponding redox derivatives, such as thapsigargin, a cytotoxic natural product with potent antitumor activity. Rapid scrambling of axial chirality of allenyl acetates in the presence of Rh(I) catalysts enables the conversion of racemic allene to enantiopure cyclopentenone product in a dynamic kinetic asymmetric transformation (DyKAT). A combined experimental and computational approach was taken to develop an effective catalytic system to achieve the asymmetric transformation. The optimization of the denticity, and steric and electronic properties of the ancillary ligand (initially (S)-MonoPhos, 58:42 er), afforded a hemilabile bidentate (S)-MonoPhos-alkene-Rh(I) catalyst that provided α-acyloxy cyclopentenone product in up to 14:86 er. Enantioselectivity of the Rh(I)-(S)-MonoPhos-alkene catalyst was rationalized using ligand-substrate steric interactions and distortion energies in the computed transition states. This asymmetric APKR of allenyl acetates is a rare example of a Type I DyKAT reaction of an allene, the first example of DyKAT in a cyclocarbonylation reaction, and the first catalyst-controlled enantioselective APKR.

Polycyclopentene-Crystal-Decorated Carbon Nanotubes by Convenient Large-Scale In Situ Polymerization and their Lotus-Leaf-Like Superhydrophobic Films.

In situ Pd-catalyzed cyclopentene polymerization in the presence of multi-walled carbon nanotubes (MWCNTs) is demonstrated to effectively render, on a large scale, polycyclopentene-crystal-decorated MWCNTs. Controlling the catalyst loading and/or time in the polymerization offers a convenient tuning of the polymer content and the morphology of the decorated MWCNTs. Appealingly, films made of the decorated carbon nanotubes through simple vacuum filtration show the characteristic lotus-leaf-like superhydrophobicity with high water contact angle (>150°), low contact angle hysteresis (<10°), and low water adhesion, while being electrically conductive. This is the first demonstration of the direct fabrication of lotus-leaf-like superhydrophobic films with solution-grown polymer-crystal-decorated carbon nanotubes.

Synthetic (+)-terrein suppresses interleukin-6/soluble interleukin-6 receptor induced-secretion of vascular endothelial growth factor in human gingival fibroblasts.

Interleukin (IL)-6 is a proinflammatory cytokine that performs a wide variety of biological functions, including important roles in the progression of chronic inflammatory diseases such as periodontal disease. (+)-Terrein, a secondary bioactive fungal metabolite isolated from Aspergillus terreus, has various biological activities; however, its anti-inflammatory effects are still unknown. The purpose of this study was to examine the effect of synthetic (+)-terrein on IL-6 signaling and related protein production in human gingival fibroblasts. To our knowledge, this study is the first to report that synthetic (+)-terrein is not cytotoxic at concentrations less than 20 µM and suppresses IL-6/soluble IL-6 receptor (sIL-6R)-induced phosphorylation of signal transducer and activator of transcription-3, extracellular signal-regulated kinase 1/2, and c-jun N-terminal kinase 1/2-signaling proteins that are downstream of IL-6 signaling. In addition, synthetic (+)-terrein suppresses IL-6/sIL-6R-induced vascular endothelial growth factor (VEGF) secretion in a concentration-dependent manner (p<0.01). These data suggest that synthetic (+)-terrein has potential anti-IL-6 signaling activity and suppresses VEGF-associated inflammatory disease progression.

First preparation of low band gap fulvene-modified polynorbornene via ring-opening metathesis polymerization.

New polymers containing intact pendant-fulvene moieties have been successfully prepared from 1,3-phenyl-6-norbornenylfulvene via ring-opening metathesis polymerization (ROMP). The prepared polyfulvenes have unique electrochemical and photophysical properties which make them interesting candidates for light harvesting materials.

Carbocyclic dinucleoside polyphosphonates: interaction with HIV reverse transcriptase and antiviral activity.

Carbocyclic alpha, gamma-bis(nucleoside)-5,5'-triphosphonates and alpha, delta-bis(nucleoside)-5,5'-tetraphosphonates (Ap4A and Gp4G) analogues were shown to be a new type of terminating substrate of HIV reverse transcriptase. They effectively inhibited the DNA synthesis catalyzed by this enzyme in model cell-free systems, but their antiviral activity both in Rat1 fibroblast cell culture bearing MLV reverse transcriptase and in HIV-infected MT-4 cells was low. When a liposome delivery system was used, the antiviral efficacy of the compounds under study was increased.

Synthesis and applications of end-labeled neoglycopolymers.

[reaction: see text] Neoglycopolymers that vary in length and contain a single fluorescent reporter group were synthesized using ring-opening metathesis polymerization (ROMP). The utility of these materials is demonstrated by the development of a cellular binding assay for L-selectin, a cell surface protein that plays a role in inflammation. The data reveal that these multivalent ligands interact with multiple copies of L-selectin.

Studies on the inhibition of tumor cell growth and microtubule assembly by 3-hydroxy-4-[(E)-(2-furyl)methylidene]methyl-3-cyclopentene-1,2-dione, an intensively coloured Maillard reaction product.

Very recently, 3-hydroxy-4-[(E)-(2-furyl)methylidene]methyl-3-cyclopentene-1,2-dione (1) has been successfully identified as an intensively coloured Maillard product formed from glucose and L-proline upon thermal food processing. Using a biomimetic synthetic strategy, reference material of compound 1 was prepared and purified, and then used to study its effect on the growth of human tumor cells. Compound 1 was found to potently inhibit the growth of human tumor cells in vitro. Using a reporter gene assay we could show that in growth inhibitory concentrations compound 1 effectively inhibits the phosphorylation of the transcription factor Elk-1. In addition, 1 was found to affect the microtubule skeleton. The human mammary carcinoma cell line MCF-7 exhibits a decrease of the microtubule organisation when treated for 24 h with 1 (> or =20 microM). At concentrations of 30 microM and above a loss of microtubule integrity is observed after 1 h incubation. In vitro studies demonstrated that the polymerisation and, to a minor extent, also the depolymerisation of tubulin, isolated and purified from bovine brain, is inhibited in a dose-dependent manner at concentrations of 30 microM and above. This is the first time that a non-enzymatically formed browning compound of known structure was reported to effectively inhibit tumor cell growth and microtubule assembly.

Self-assembly of photochromic diarylethenes with amphiphilic side chains: core-chain ratio dependence on supramolecular structures.

Photochromic diarylethene derivatives having different lengths and numbers of poly(ethylene glycol) side chains were synthesized and their photochromic property and self-assembling behavior were investigated. The self-assembling behavior of the derivatives strongly depends upon the ratio between the hydrophobic core and the amphiphilic side chain. According to UV/Vis absorption spectroscopy, CD spectroscopy, and dynamic light scattering experiments, these derivatives showed different size distribution of the assembled structures and different solubility in water. The intensity of the induced CD signal, which was observed in the closed-ring isomer, was the largest for the molecule having two hexaethylene glycol side chains. The relationship between the core-chain ratio and regularity of the self-assembled structure has been investigated.