Norbornene

About: Norbornene is a research topic. Over the lifetime, 5628 publications have been published within this topic receiving 104495 citations. The topic is also known as: norbornylene & norcamphene.

Nickel catalysis of olefin epoxidation

Abstract: Etude de l'epoxydation catalytique des olefines par une large variete de complexes du nickel II, derivant de differents macrocycles tetraaza, bases de Schiff, porphyrines et phosphines bidentes

A genetically encoded norbornene amino acid for the mild and selective modification of proteins in a copper-free click reaction.

Abstract: Methods for the site-specific chemical modification of proteins are currently of immense importance for the synthesis of protein–hybrid compounds for pharmaceutical and diagnostic purposes. Most of the methods rely on the reaction of free protein thiols with maleimides or the reaction of lysine side chains with activated esters. These methods provide only limited specificity, which is prompting researchers to develop alternative strategies that involve the incorporation of special unnatural amino acid into proteins to enable site-specific bioorthogonal functionalization. Among the developed methods, the Cu-catalyzed reaction of a protein containing an alkyne amino acid with azides stands out as the most thoroughly investigated technology. 6] However, the need for Cu salts, which may harm the protein structure, limits the technology. This fuels current interest to develop copperfree coupling reactions that are compatible with fragile protein structures. Here we show that these requirments can be met with a specially encoded norbornene amino acid which reacts selectively with nitrile imines. In order to insert a norbornene amino acid into a protein we used the amber suppression technique based on the pyrrolysyl tRNA/pyrrolysyl-tRNA synthetase (tRNA/ PylRS) pair from Methanosarcina mazei. The main task of the project was to evolve the pyrrolysine synthetase so that it accepts the synthetic norbornene amino acid 1 (Scheme 1 a) for loading onto the pyrrolysyl-tRNA. For the study we synthesized the norbornene-containing Pyl analogue 1 in seven steps from readily available starting materials (see the Supporting Information). To test to what extent 1 is accepted by wild-type (wt) PylRS, we used E. coli cells encoding the full tRNA/PylRS pair and a modified yellow fluorescent protein (YFP) containing one in-frame TAG stop codon. In this system the full-length and hence fluorescent YFP can only be produced when the corresponding Pyl analogue is accepted by the PylRS and successfully loaded onto the tRNA for subsequent incorporation into the protein at the amber stop codon site. The so-prepared E. coli cells were grown in a medium containing 5 mm 1. In addition to the wild-type PylRS we also tested a PylRS mutant (Y384F) previously used by Yanagisawa and co-workers. These initial experiments provided a just faint fluorescence when the mutant PylRS(Y384F) was used. No flurescence and hence no full-length YFP was generated in the presence of wild-type PylRS. In order to increase the PylRS activity we evolved the protein using iterative saturation mutagenesis (ISM) developed by Reetz and co-workers. Based on the co-crystal structure of PylRS in complex with adenylated pyrrolysine (PDB 2Q7H) we selected five residues in the substrate-binding pocket of wt-PylRS for the experiments. After transformation of the plasmid-based PylRS library into E. coli, single colonies were grown in liquid cultures supplemented with 1. The incorporation was monitored by means of the YFP fluorescence intensity of the cells. The most efficient PylRS variants were then sequenced and used in the next round of the saturation mutagenesis. In Scheme 1. a) Structure of norbornene Pyl analogue 1 and b) schematic representation of the click reactions. Top: A nitrile imine is generated by base-promoted HCl elimination from the hydrazonoyl chloride and then used in a cycloaddition reaction with the norbornene. Middle: Alternatively the nitrile imine is generated from a tetrazole in a photochemical reaction. Bottom: The norbornene modification can also react with tetrazines in a reversed-electron-demand Diels–Alder reaction. (Protein representations generated from PDB 3IN5.)

Controlled copolymerization of methyl acrylate with olefins under mild conditions

Abstract: A copper-mediated process for the synthesis of random copolymers of methyl acrylate with non-polarolefins, ranging from ethene to 1-octene, norbornene and norbornene derivatives, and capable of synthesizing copolymers having greater than 5% incorporation of the olefin, as well as copolymers synthesized using the process are described. The process displays many of the characteristics of a living polymerization process: the polydispersities of the copolymers obtained are less than about 1.7, preferably from about 1.1 to about 1.4, and it is possible to synthesize novel block terpolymers of methyl acrylate with olefins by the sequential addition of the latter monomers.

Cis-selective ring-opening metathesis polymerization with ruthenium catalysts.

Abstract: Cis-selective ring-opening metathesis polymerization of several monocyclic alkenes as well as norbornene and oxanorbornene-type monomers using a C–H activated, ruthenium-based metathesis catalyst is reported. The cis content of the isolated polymers depended heavily on the monomer structure and temperature. A cis content as high as 96% could be obtained by lowering the temperature of the polymerization.