Orthogonal Agent Comprising a Nitrile N-Oxide and a Phenylcarbamate for Facile Molecular Integration on Styrne-Butadiene Resin.

The covalent attachment of poly(ethylene glycol) (PEGylation) to materials minimizes non-specific fouling of the material surface with biocomponents. While the PEGylation reaction on polar surfaces is widely used and regarded as a common technique, the PEGylation on less polar polymers and elastomers is extremely difficult due to the absence of reactive points with PEG terminus. Herein, the design and synthesis of an orthogonal agent with a nitrile N-oxide and a phenyl carbamate that can mediate between an alkene and an amine are reported.

Kinetic Gas Hydrate Inhibition by Alternating Dipeptoids with Optimal Size and Shape -Substituents.

Current commercial kinetic hydrate inhibitors (KHIs) are all based on water-soluble polymers with amphiphilic alkylamide or lactam groups. The size and shape of the hydrophobic moiety are known to be critical for optimum KHI performance. Proteins and peptides represent an environmentally friendly alternative, especially as bioengineering could be used to manufacture a product predetermined to have optimum KHI performance.

Synthesis and self-assembly behaviors of α-galactosyl ceramide (1,2)-polysaccharide analogue.

α-Galactosyl ceramide (GalCer) as a glycolipid has been long used as a standard reference for positive control in natural killer T cell studies. The (1,2)-disaccharide analogue of GalCer attracts a special attention in the study of lysosomal glycolipid processing. This paper describes the synthesis and self-assembly behaviors of GalCer 1,2-polysaccharide analogue (PolyGalCer), having considered the 1,2-disaccharide analogue as a structural motif.

Dansylated Nitrile N-Oxide as the Fluorescent Dye Clickable to Unsaturated Bonds without Catalyst.

Fluorescent polymeric materials have been exploited in the fields of aesthetical purposes, biomedical engineering, and three-dimensional printing applications. While the fluorescent materials are prepared by the polymerization of fluorescent monomer or the blending a fluorescent dye with common polymer, the covalent immobilization of fluorescent dye onto common polymers is not the practical technique. In this paper, dansylated nitrile N-oxide (Dansyl-NO) has been designed and synthesized to be a stable nitrile N-oxide as the derivative of 2-hydroxy-1-naphthaldehyde.

Synthesis and Conformational Behaviors of Unnatural Peptides Alternating Chiral and Achiral α,α-Disubstituted α-Amino Acid Units.

The development of peptidomimetics to modulate the conformational profile of peptides has been extensively studied in the fields of biological and medicinal chemistry. However, large-scale synthesis of peptidomimetics with both an ordered sequence and a controlled secondary structure is highly challenging. In this paper, the framework of peptidomimetics has been designed to be alternating an achiral α,α-disubstituted α-amino acid unit and a chiral α-methylphenylalanine unit.

Efficient Transformation of Polymer Main Chain Catalyzed by Macrocycle Metal Complexes via Pseudorotaxane Intermediate.

Post-synthesis modification of polymers streamlines the synthesis of functionalized polymers, but is often incomplete due to the negative polymer effects. Developing efficient polymer reactions in artificial systems thus represents a long-standing objective in the fields of polymer and material science. Here, we show unprecedented macrocycle-metal-complex-catalyzed systems for efficient polymer reaction that result in 100 % transformation of the main chain functional groups presumably via a processive mode reaction.

Effects of Glycon and Temperature on Self-Assembly Behaviors of α-Galactosyl Ceramide in Water.

α-Galactosyl ceramide () is an anticancer glycolipid consisting of d-galactose and phytosphingosine-based ceramide. Although the amphiphilic structure of is expected to form self-associates in water, the self-assembly behaviors of and its derivatives have not been systematically investigated at this moment in spite of its great importance. The evaluation of morphologies and properties of the associates should open new insights into glycolipid chemistry such as the application of derivatives to a nanocarrier and the elucidation of the detailed pharmacological mechanism of .

Shear-Induced Adhesion of Alternating Peptides Prepared by Ugi Four-Center Three-Component Reaction.

The development of new peptide-based glues has been strongly urged from the viewpoints of industrial applications and biomedical engineering. However, the large-scale synthesis of polypeptides with an ordered sequence is highly challenging, which strictly restricts materials resources for the research and development of polypeptides. In this work, the framework of adhesive alternating peptides has been designed to be glycine (Gly)-N-substituted valine (Val) as the dipeptide repeating sequence, considering the peptapeptide repeating sequence of viscoelastic natural elastin as a motif.

Thermoresponsive Structure and Dye Encapsulation of Micelles Comprising Bolaamphiphilic Quercetin Polyglycoside.

A bolaamphiphile is a special member of amphiphilic molecules, which contains a hydrophobic skeleton and two water-soluble groups on both ends. Bolaamphiphiles form thermally stable associates in water under lower concentration than those of typical monoheaded amphiphiles, indicating the potential usefulness of bolaamphiphiles as the component of nanomaterials. However, the structural diversity of bolaamphiphiles is limited at this moment.

Substituent Optimization of (1 → 2)-Glucopyranan for Tough, Strong, and Highly Stretchable Film with Dynamic Interchain Interactions.

Polysaccharide is a naturally abundant material, which is regarded as an indispensable scaffold for a structural material. The properties of polysaccharides are dependent not only on the structure of repeating sugar unit but also the glycosidic position between the repeating units. Herein, we report the development of polysaccharide-based self-standing film consisting of naturally occurring (1 → 2)-glucopyranan skeleton.

Strong, tough, and repeatable adhesion of an alternating peptide comprising phenyl glycine as a repeating unit.

A new strategy for preparing peptide-based adhesive materials is provided. An exactly alternating peptide with glycine-N-butylphenyl glycine dipeptide repeating units exhibits excellent repeatable adhesion capacity. The adhesive properties are attributed to the viscoelastic properties and microfibril formation, which are tunable by simple manipulation of the reaction component on polymerization.

Bolaamphiphilic properties and pH-dependent micellization of quercetin polyglycoside.

Quercetin polyglycoside as a new bolaamphiphile is prepared a one-pot grafting polymerization technique using sugar-based cyclic sulfite. Micelles comprising quercetin polyglycoside exhibit special pH-effects, in which the polyglycoside moieties on the surface of the micelle serve as a steric protecting group to endow chemical stabilization.

Effects of the Hydrophilic-Lipophilic Balance of Alternating Peptides on Self-Assembly and Thermo-Responsive Behaviors.

A series of -substituted poly(Gly-alter-Val) peptides were successfully synthesized for the systematic evaluation of the micellization behavior of alternating peptides. Three-component polymerization employing an aldehyde, a primary ammonium chloride, and potassium isocyanoacetate afforded four alternating peptides in excellent yields. We investigated the dependence of the hydrophilic-lipophilic balance of alternating peptides on the micellization behavior.

Structural factors of benzylated glucopyranans for shear-induced adhesion.

We have prepared benzylated glucopyranans and evaluated the structural effects on the adhesion capacity. It was found that 97%-benzylated (1→2)-glucopyranan exhibited a unique shear-induced adhesion. The effects of structural factors on the adhesion behaviors are discussed through systematic adhesion tests, differential scanning calorimetry, theoretical models, and IR spectroscopy.

Induction of Single-Handed Helicity of Polyacetylenes Using Mechanically Chiral Rotaxanes as Chiral Sources.

Effective induction of preferred-handed helicity of polyacetylenes by pendant mechanically chiral rotaxanes is discussed. Polyacetylenes possessing optically active mechanically chiral rotaxanes in the side chains were synthesized by the polymerization of the corresponding enantiopure [2]rotaxane-type ethynyl monomers prepared by the chiral-phase HPLC separations. The CD Cotton effects revealed that the polyacetylenes took preferred-handed helical conformations depending on the rotaxane chirality.

One-pot synthesis of alternating peptides exploiting a new polymerization technique based on Ugi's 4CC reaction.

We developed a one-pot synthetic technique for alternating peptides. Central to this technique is a new, catalyst-free polymerization based on Ugi's 4CC reaction. The treatment of imines with the ambident molecules bearing both an isocyanide and a carboxylic acid afforded alternating peptides.

One-pot synthesis of glycyrrhetic acid polyglycosides based on grafting-from method using cyclic sulfite.

Glycyrrhetic acid polyglycosides were synthesized in one-pot via cationic ring-opening condensation polymerization of cyclic sulfite () initiated by glycyrrhetic acid as an aglycon. Sulfite worked as a practical monomer for the preparation of (1 → 2)-linked polysaccharide skeletons. The chemical stability of was evaluated by the comparison of thermodynamic parameters with those of conventional epoxide ().

Structural Analysis and Inclusion Mechanism of Native and Permethylated α-Cyclodextrin-Based Rotaxanes Containing Alkylene Axles.

Native α-cyclodextrin- (α-CD) and permethylated α-CD (PMeCD)-based rotaxanes with various short alkylene chains as axles can be synthesized through a urea end-capping method. Native α-CD tends to form [3]- or [5]pseudorotaxanes and not [2]- or [4]pseudorotaxanes, which indicates that the coupled CDs act as a single fragment. End-capping reactions of the pseudorotaxanes with C18 and C24 axle lengths do not occur because the axle termini are covered by the densely stacked CDs.

Thermotriggered Catalyst-Free Modification of a Glass Surface with an Orthogonal Agent Possessing Nitrile N-Oxide and Masked Ketene Functions.

The thermotriggered modification of surfaces was performed under catalyst-free conditions using an orthogonal agent possessing both nitrile N-oxide and Meldrum's acid moieties. The nitrile N-oxide moiety of the orthogonal agent successfully underwent catalyst-free 1,3-dipolar cycloaddition to unsaturated bonds of glass surfaces to produce Meldrum's acid-functionalized surfaces. The subsequent thermal decomposition of Meldrum's acid moiety in the presence of nucleophiles afforded versatile nucleophile-modified surfaces (e.

Exact helical polymer synthesis by a two-point-covalent-linking protocol between C2-chiral spirobifluorene and C2- or C(s)-symmetric anthraquinone monomers.

Two types of one-handed exact helical polymers, coil- and screw-shaped polymers, were synthesized by the two-point-covalent-linking protocol using C2-chiral spirobifluorene (SBF) and C2- or C(s)-symmetric anthraquinone spacers. Central to this protocol is a new aromatic ring-forming reaction based on the stepwise reductive cyclization of bis(aryloxy group)-substituted anthraquinone derivatives. The helical structures of the polymers annulated by aromatic skeletons exhibited high thermal stability attributed to the rigid C2-chiral SBF units and the covalently two-point-connected structure.

Reversible Transformation of a One-Handed Helical Foldamer Utilizing a Planarity-Switchable Spacer and -Chiral Spirobifluorene Units.

Polymeric quaterthiophenes containing optically active -chiral spirobifluorene skeletons were synthesized as a new type of helical foldamers, and their higher-order structures were investigated. Oxidization of quaterthiophene moieties caused the spacer units to be in planar structure, leading the conformation of the polymer to be a coil-shaped, rigid helix. This transformation was reversibly performed.

Linear-cyclic polymer structural transformation and its reversible control using a rational rotaxane strategy.

Linear-cyclic polymer structural transformation and its reversibility are demonstrated by a simple but rational strategy using the structural characteristics of crown ether-based rotaxanes. The structure of a polymer containing a [1]rotaxane unit at one end was controlled by conventional protection-deprotection reactions, giving rise to a reversible linear-cyclic polymer structural transformation.

Cyclodextrin-based size-complementary [3]rotaxanes: selective synthesis and specific dissociation.

α-Cyclodextrin (CD)-based size-complementary [3]rotaxanes with alkylene axles were prepared in one-pot by end-capping reactions with aryl isocyanates in water. The selective formation of [3]rotaxane with a head-to-head regularity was indicated by the X-ray structural analyses. Thermal degradation of the [3]rotaxanes bearing appropriate end groups proceeded by stepwise dissociation to yield not only the original components but also [2]rotaxanes.

Synthesis of Highly Reactive Polymer Nitrile -Oxides for Effective Solvent-Free Grafting.

A one-pot synthesis of polymer nitrile -oxides was achieved via the Michael addition of living polymer anions derived from vinyl monomers to commercially available -β-nitrostyrene and subsequent dehydration with concd HSO. The polymer nitrile -oxides are effective as grafting agents in catalyst- and solvent-free 1,3-dipolar cycloadditions to unsaturated-bond-containing polymers with high conversion and exhibit higher reactivity compared to that of nitrile -oxides prepared from 1,1-diphenylnitroethene. Application to the preparation of a functional glass surface was demonstrated using PBMA nitrile -oxide as a grafting agent.

Fluorescence control of boron enaminoketonate using a rotaxane shuttle.

The effect of rotaxane shuttling on the fluorescence properties of a fluorophore was investigated by exploiting fluorophore-tethered [2]rotaxanes. A fluorescent boron enaminoketonate (BEK) moiety was introduced in a rotaxane via transformation of an isoxazole unit generated as a result of an end-capping reaction using a nitrile N-oxide. The rotaxane exhibited a red shift of the fluorescence maximum along with a remarkable enhancement of the fluorescence quantum yield through wheel translation to the fluorophore.