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Nishio M.,CHPI Institute | Umezawa Y.,Institute of Microbial Chemistry BIKAKEN Tokyo | Fantini J.,Aix - Marseille University | Weiss M.S.,Helmholtz Center Berlin | Chakrabarti P.,Bose Institute of India
Physical Chemistry Chemical Physics | Year: 2014

This is a sequel to the previous Perspective "The CH-π hydrogen bond in chemistry. Conformation, supramolecules, optical resolution and interactions involving carbohydrates", which featured in a PCCP themed issue on "Weak Hydrogen Bonds-Strong Effects?": Phys. Chem. Chem. Phys., 2011, 13, 13873-13900. Evidence that weak hydrogen bonds play an enormously important role in chemistry and biochemistry has now accumulated to an extent that the rigid classical concept of hydrogen bonds formulated by Pauling needs to be seriously revised and extended. The concept of a more generalized hydrogen bond definition is indispensable for understanding the folding mechanisms of proteins. The CH-π hydrogen bond, a weak molecular force occurring between a soft acid CH and a soft base π-electron system, among all is one of the most important and plays a functional role in defining the conformation and stability of 3D structures as well as in many molecular recognition events. This concept is also valuable in structure-based drug design efforts. Despite their frequent occurrence in organic molecules and bio-molecules, the importance of CH-π hydrogen bonds is still largely unknown to many chemists and biochemists. Here we present a review that deals with the evidence, nature, characteristics and consequences of the CH-π hydrogen bond in biological macromolecules (proteins, nucleic acids, lipids and polysaccharides). It is hoped that the present Perspective will show the importance of CH-π hydrogen bonds and stimulate interest in the interactions of biological macromolecules, one of the most fascinating fields in bioorganic chemistry. Implication of this concept is enormous and valuable in the scientific community. This journal is © the Partner Organisations 2014.

Cui J.,Osaka University | Cui J.,Institute of Microbial Chemistry BIKAKEN Tokyo | Kawatake S.,Osaka University | Umegawa Y.,Osaka University | And 7 more authors.
Organic and Biomolecular Chemistry | Year: 2015

Phosphatidylglycerophosphate methyl ester (PGP-Me), a major constituent of the archaeal purple membrane, is essential for the proper proton-pump activity of bacteriorhodopsin (bR). We carried out the first synthesis of the bisphosphate head group of PGP-Me using H-phosphonate chemistry that led to the production of a simplified PGP-Me analogue with straight alkyl chains. To investigate the role of this head group in the structural and functional integrity of bR, the analogue was used to reconstitute bR into liposomes, in which bR retained the original trimeric structure and light-induced photocycle activity. Enhanced ordering of an alkyl chain of the 2H-labelled analogue was observed in 2H NMR spectra upon interaction with bR. These results together suggest that the bisphosphate moiety plays a role in the proper functioning of bR through the lipid-protein interaction. © The Royal Society of Chemistry 2015.

Umezawa Y.,Institute of Microbial Chemistry BIKAKEN Tokyo | Nishio M.,CHPI Institute
Supramolecular Chemistry | Year: 2013

A crystallographic database study was carried out to investigate the potentiality of guanidinium group acting as an effective CH acceptor (π-donor) of the CH/π hydrogen bond; it has been demonstrated that this group is a good receptor of CH in crystals of arginine and its derivatives. Implication of the present finding to protein biochemistry and rational drug design is suggested. © 2013 © 2013 Taylor & Francis.

Hashimoto K.,Institute of Microbial Chemistry BIKAKEN Tokyo | Kumagai N.,Institute of Microbial Chemistry BIKAKEN Tokyo | Shibasaki M.,Institute of Microbial Chemistry BIKAKEN Tokyo | Shibasaki M.,Japan Science and Technology Agency
Chemistry - A European Journal | Year: 2015

A readily recyclable asymmetric catalyst has been developed based on the self-assembly of a homogeneous catalyst in a fibrous network of multiwalled carbon nanotubes (MWNTs). Dimerization of an amide-based chiral ligand with a suitable spacer allows for the efficient formation of a heterogeneous catalyst by self-assembly on addition of Er(OiPr)3. The self-assembly proceeds in the MWNT fibrous network and small clusters of assembled catalyst are confined in the MWNTs, producing an easily handled solid-phase catalyst. The resulting MWNT-confined catalyst exhibits a good catalytic performance in a catalytic asymmetric Mannich-type reaction, which can be conducted in a repeated batch system and in a continuous-flow platform. © 2015 Wiley-VCH Verlag GmbH & Co. KGaA.

Tamura K.,Institute of Microbial Chemistry BIKAKEN Tokyo | Kumagai N.,Institute of Microbial Chemistry BIKAKEN Tokyo | Shibasaki M.,Institute of Microbial Chemistry BIKAKEN Tokyo | Shibasaki M.,Japan Science and Technology Agency
European Journal of Organic Chemistry | Year: 2015

A direct catalytic asymmetric Mannich-type reaction of benzyl isocyanide using a CuI catalyst and N-(diphenylthiophosphinoyl)imines was developed. The simultaneous activation strategy by soft-soft interaction was the key to promote the reaction using a weakly acidic pronucleophile, benzyl isocyanide. The spontaneous cyclization of the Mannich adduct afforded the corresponding enantioenriched imidazolines, which could be precursors for a variety of 1,2-diarylethylenediamines. Enantioenriched 4,5-diarylimidazolines were directly accessed by catalytic asymmetric C-C bond-forming reaction of benzyl isocyanide and N-(thiophosphinoyl)aldimines. The imidazolines were readily transformed into enantioenriched 1,2-diarylethylenediamines. Copyright © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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