Complexation Stabilized Conformational Regulation of Ferrocene Bearing Podand Dipeptide Chains (-l-Ala-l-Pro-NHPy)

The structural characterization of the palladium complex of the ferrocene 1 bearing podand dipeptide chains (-l-Ala-l-Pro-NHPy) was demonstrated. The ferrocene 1 forms the 1:1 trans complex 2 with PdCl2(MeCN)2 to stabilize the intramolecular conformational regulation in both solution and solid states. The crystal structure of 2 revealed a pseudohelical conformation through palladium binding and chirality organization via sterically constrained moieties (Pro) and intramolecular hydrogen bondings between CO (Ala) and NH (another Ala) of each podand dipeptide chain (N(1)···O(2*), 2.88 Å; N(1*)···O(2), 2.97 Å), giving a 10-membered hydrogen-bonded ring. Such an ordered conformation was supported by the induced circular dichroism. Another noteworthy feature of the ferrocene 1 is its strong tendency to self-assemble through participation of all available hydrogen-bonding donors in the solid state

Self-Assembly of Dipeptidyl Ureas: A New Class of Hydrogen-Bonded Molecular Duplexes

The dipeptidyl urea 1 composed of two dipeptide chains bearing the C-terminal pyridyl moiety (-l-Ala-l-Pro-NHPy) was prepared. Two molecules of 1 are revealed to be held together by six intermolecular hydrogen bonds to form a hydrogen-bonded duplex by the single-crystal X-ray structure determination. Proton magnetic resonance nuclear Overhauser effect (NOE) study indicates the hydrogen-bonded duplex even in solution. Furthermore, a shuttle-like molecular dynamics based on recombination of the hydrogen bonds was observed. The dipeptidyl urea composed of two dipeptide chains bearing the C-terminal pyrenyl moiety (-l-Ala-l-Pro-NHCH2Pyr) exhibited both monomer and eximer emissions in the fluorescence spectra, supporting the formation of a duplex. A combination of the C-terminal amide NH function in each side and the designed sequence of hydrogen-bonding sites are considered to be a crucial factor for the duplex formation

Chirality-Organized Ferrocene Receptor Bearing Podand Dipeptide Chains (−l-Ala-l-Pro-NHPyMe) for the Selective Recognition of Dicarboxylic Acids

The ferrocene receptor bearing the podand dipeptide chains (−l-Ala-l-Pro-NHPyMe) was found to provide a chirality-organized binding site through two intramolecular interchain hydrogen bonds between CO (Ala) and NH (another Ala) of each podand dipeptide chain. The size-selective and chiral recognition of dicarboxylic acids was achieved by multipoint hydrogen bonds of the binding site

Complexation Stabilized Conformational Regulation of Ferrocene Bearing Podand Dipeptide Chains (-l-Ala-l-Pro-NHPy)

The structural characterization of the palladium complex of the ferrocene 1 bearing podand dipeptide chains (-l-Ala-l-Pro-NHPy) was demonstrated. The ferrocene 1 forms the 1:1 trans complex 2 with PdCl2(MeCN)2 to stabilize the intramolecular conformational regulation in both solution and solid states. The crystal structure of 2 revealed a pseudohelical conformation through palladium binding and chirality organization via sterically constrained moieties (Pro) and intramolecular hydrogen bondings between CO (Ala) and NH (another Ala) of each podand dipeptide chain (N(1)···O(2*), 2.88 Å; N(1*)···O(2), 2.97 Å), giving a 10-membered hydrogen-bonded ring. Such an ordered conformation was supported by the induced circular dichroism. Another noteworthy feature of the ferrocene 1 is its strong tendency to self-assemble through participation of all available hydrogen-bonding donors in the solid state

Chirality Organization of Ferrocenes Bearing Dipeptide Chains of Heterochiral Sequence

The symmetrical introduction of two dipeptide chains of heterochiral sequence (-l-Ala-d-Pro-NHPy) into the ferrocene scaffold as a central reverse-turn unit was demonstrated to induce both antiparallel β-sheet-like and type II β-turn-like structures simultaneously, affording the chirality-organized structure. The ferrocene bearing only one dipeptide chain (-l-Ala-d-Pro-NHPy) exhibited a left-handed helically ordered molecular assembly through a network of intermolecular hydrogen bonds instead of intramolecular hydrogen bonds

Oxovanadium(V)-Catalyzed Synthesis of Unsymmetrical Ureas by Activation of Carbon Dioxide under Ambient Pressure

A sustainable approach for the catalytic synthesis of unsymmetrical ureas from disilylamines through catalytic activation of carbon dioxide as a C1 building block under ambient pressure was performed by using a commercially available easy-to-handle NH4VO3. This catalytic system displayed a wide range of substrate applicability without the use of any dehydrating reagents or bases. Gram-scale catalytic reaction was successfully performed to validate the scalability of this catalytic synthesis of unsymmetrical ureas under ambient carbon dioxide pressure

Chirality Organization of Ferrocenes Bearing Dipeptide Chains of Heterochiral Sequence

The symmetrical introduction of two dipeptide chains of heterochiral sequence (-l-Ala-d-Pro-NHPy) into the ferrocene scaffold as a central reverse-turn unit was demonstrated to induce both antiparallel β-sheet-like and type II β-turn-like structures simultaneously, affording the chirality-organized structure. The ferrocene bearing only one dipeptide chain (-l-Ala-d-Pro-NHPy) exhibited a left-handed helically ordered molecular assembly through a network of intermolecular hydrogen bonds instead of intramolecular hydrogen bonds

Chirality Organization of Aniline Oligomers through Hydrogen Bonds of Amino Acid Moieties

Aniline oligomers bearing amino acid moieties were designed by the introduction of l/d-Ala-OMe into aniline oligomers to induce chirality organization of the π-conjugated aniline oligomer moieties, wherein the formation of intramolecular hydrogen bonds was demonstrated to play an important role to regulate the aniline oligomer moieties conformationally

Chirality Organization of Aniline Oligomers through Hydrogen Bonds of Amino Acid Moieties

Aniline oligomers bearing amino acid moieties were designed by the introduction of l/d-Ala-OMe into aniline oligomers to induce chirality organization of the π-conjugated aniline oligomer moieties, wherein the formation of intramolecular hydrogen bonds was demonstrated to play an important role to regulate the aniline oligomer moieties conformationally

Induction of γ-Turn-Like Structure in Ferrocene Bearing Dipeptide Chains via Conformational Control

A combination of the ferrocene scaffold as a central reverse-turn unit with the dipeptide chains (-l-Pro-l-Ala-NHPy) was demonstrated to induce both inverse γ-turn-like and antiparallel β-sheet-like structures. Only the antiparallel β-sheet-like structure was formed in the ferrocene bearing the heterochiral dipeptide chains (-l-Pro-d-Ala-NHPy), in which highly organized self-assembly was achieved through a network of intermolecular hydrogen bonds