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en: Improvement of Asymmetric Reactions via Remote Electronic Tuning of N-Heterocyclic Carbene Catalysts

en: ChemCatChem

ja: ChemCatChem


en: Remote Electronic Tuning for High-performance N-Heterocyclic Carbene Catalysis

ja: 遠隔位電子チューニングによるN-複素環式カルベン触媒の高性能化

en: Journal of Synthetic Organic Chemistry, Japan

ja: 有機合成化学協会誌


en: Remote Electronic Tuning of Chiral N-Heterocyclic Carbenes

en: Our recent efforts to develop novel N-Heterocyclic carbene (NHC)-catalyzed asymmetric reactions are described. During our investigation for development of the acylation reactions via acylazoliums generated by the reactions of NHCs and α-oxidized aldehydes, we have observed significant effects of substitution at a remote site of the carbene carbon of NHCs. In addition, we also observed a significant enhancement of the enantioselectivity by the addition of carboxylate anions. From this observation, we proposed a novel working hypothesis involving a formation of a complex of the substrate and additive to reinforce the recognition of the catalyst for enhancement of the catalytic performance of the asymmetric N-heterocyclic carbene system. By applying this concept, we achieved the kinetic resolutions of both cyclic and acyclic alcohols in excellent enantioselectivities. The effects of the remote substitution were also observed in intramolecular Stetter reaction and intermolecular benzoin reaction. In these reactions, the comparison of the catalytic performance of the NHCs bearing variable remote substitutions provided insights into the reaction mechanism because the remote substitution tuned the electronic nature of NHCs without affecting the steric and electrostatic factors around the reaction site. We also developed an intramolecular benzoin condensation involving two aldehydes, which is challenging to realize. Using the substrates bearing proper protecting groups, we succeeded in the stereo divergent synthesis of a variety of inososes, which are important intermediates for the synthesis of biologically active cyclitols.

en: Chemical Record

ja: Chemical Record


en: Synthesis of Non-canonical Amino Acids and Peptide Containing Them for Establishment of the Template for Drug Discovery

en: Chemical & Pharmaceutical Bulletin

ja: Chemical & Pharmaceutical Bulletin


en: Invention of stimulus-responsive peptide-bond-cleaving residue (Spr) and its application to chemical biology tools

en: Elucidation of biological functions of peptides and proteins is essential for understanding peptide/protein-related biological events and developing drugs. Caged peptides and proteins that release a parent active peptide/protein by photo-irradiation have successfully been employed to elucidate the functions. Whereas the usual caged peptide/protein enables conversion of an inactive form to an active form (OFF-to-ON conversion) by photo-induced deprotection, photo-triggered main chain cleavage is reported to be applicable to ON-to-OFF conversion. These peptides and proteins are photo-responsive; however, if peptides and proteins could respond to other stimuli such as disease-related environment or enzymes, their range of application should be widened. To convert the photo-responsive peptide/protein into other stimulus-responsive peptide/protein, quite laborious de novo design and synthesis of the stimulus-responsive unit are required. In this context, we designed a stimulus-responsive peptide-bond-cleaving residue (Spr) in which the stimuli available for the main chain cleavage vary according to the choice of protecting groups on the residue. In this review, design and synthesis of Spr are introduced, and challenges to apply Spr to other fields to enable, for example, functional control, localization control, delivery of cargos, labeling of a protein of interest in living cells, and identification of target proteins of bioactive ligands are discussed. Copyright © 2017 European Peptide Society and John Wiley & Sons, Ltd.

en: Journal of Peptide Science

ja: Journal of Peptide Science


en: 天然アミノ酸配列に適用可能な新規タンパク質チオエステル合成法の開発

ja: 天然アミノ酸配列に適用可能な新規タンパク質チオエステル合成法の開発

en: ケミカルバイオロジー

ja: ケミカルバイオロジー


en: Development of Innovative HydrogenBondDonor Catalysts Based on Heterocyclic Scaff olds and Their Applications to Asymmetric Reactions

ja: 複素環骨格を基盤とする新規水素結合供与型有機分子触媒の開発と不斉反応への応用

en: We have designed and synthesized novel bifunctional hydrogen-bond (HB) donor catalysts bearing a benzothiadiazine or a quinazoline scaffold, whose HB-donating activity as well as recognition modes of the substrates were found to be significantly different from thiourea-typed organocatalysts by comparison of their 1H NMR studies, X-ray crystallographic analyses, spectrophotometric analyses, and computational investigations. We found that quinazoline-typed catalysts were effective for the highly enantioselective hydrazination of 1,3-dicarbonyl compounds and that benzothiadiazine-type catalysts showed great activity for the asymmetric isomerization of alkynoates to allenoates. In both cases, these newly developed catalysts were much more efficient than thiourea-typed organocatalysts, indicating that the HB-donating moiety of the catalysts was important for the recognition and activation of the substrates to facilitate the reaction.