Liquid interfaces are unique environments in which a variety of fundamental phenomena occur. Therefore, it is important to obtain a molecular-level understanding of liquid interfaces for both basic science and industrial applications. However, it is not an easy task to investigate molecules in the interface region that only has nanometer thicknesses. Second-order nonlinear spectroscopy, or even-order nonlinear spectroscopy more generally, is intrinsically interface-selective because the relevant nonlinear signal is generated only in the region in which the inversion symmetry is broken under the dipole approximation. In the past 2 decades, we have been developing and applying new interface nonlinear spectroscopic methods, aiming to bring up the level of knowledge on interfacial molecules to that on molecules in solution. During this attempt, we developed electronic sum-frequency generation spectroscopy, heterodyne-detected electronic sum-frequency generation spectroscopy, and heterodyne-detected vibrational sum-frequency generation spectroscopy, as well as fourth-order Raman spectroscopy. We also extended the methods to femtosecond time-resolved measurements. Using these methods, we are now able to study the structure and dynamics at liquid interfaces, in particular exposed interfaces such as air/liquid interfaces, at a similar level to the study for solution. I overview our interface research while describing thoughts we had at each turning point.
{"title":"Working on a dream: bringing up the level of interface spectroscopy to the bulk level","authors":"Tahei Tahara","doi":"10.1093/bulcsj/uoae012","DOIUrl":"https://doi.org/10.1093/bulcsj/uoae012","url":null,"abstract":"\u0000 Liquid interfaces are unique environments in which a variety of fundamental phenomena occur. Therefore, it is important to obtain a molecular-level understanding of liquid interfaces for both basic science and industrial applications. However, it is not an easy task to investigate molecules in the interface region that only has nanometer thicknesses. Second-order nonlinear spectroscopy, or even-order nonlinear spectroscopy more generally, is intrinsically interface-selective because the relevant nonlinear signal is generated only in the region in which the inversion symmetry is broken under the dipole approximation. In the past 2 decades, we have been developing and applying new interface nonlinear spectroscopic methods, aiming to bring up the level of knowledge on interfacial molecules to that on molecules in solution. During this attempt, we developed electronic sum-frequency generation spectroscopy, heterodyne-detected electronic sum-frequency generation spectroscopy, and heterodyne-detected vibrational sum-frequency generation spectroscopy, as well as fourth-order Raman spectroscopy. We also extended the methods to femtosecond time-resolved measurements. Using these methods, we are now able to study the structure and dynamics at liquid interfaces, in particular exposed interfaces such as air/liquid interfaces, at a similar level to the study for solution. I overview our interface research while describing thoughts we had at each turning point.","PeriodicalId":9511,"journal":{"name":"Bulletin of the Chemical Society of Japan","volume":null,"pages":null},"PeriodicalIF":4.0,"publicationDate":"2024-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140368665","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Six platinum complexes bearing monodentate phosphine ligands were prepared and their structures and photophysical properties examined. The complexes were photoluminescent in the solid state, with a maximum quantum yield of 72%. The tris(phosphine) platinum complexes displayed more red-shifted emissions than the tetrakis complexes. The nature of the emissive excited states is discussed based on the results of density functional theory and time-dependent density-functional theory calculations.
{"title":"Photoluminescence of Three- and Four-Coordinate Platinum(0) Phosphine Complexes","authors":"Yoji Mizumoto, Mio Murao, Yasuomi Yamazaki, Taro Tsubomura","doi":"10.1093/bulcsj/uoae035","DOIUrl":"https://doi.org/10.1093/bulcsj/uoae035","url":null,"abstract":"\u0000 Six platinum complexes bearing monodentate phosphine ligands were prepared and their structures and photophysical properties examined. The complexes were photoluminescent in the solid state, with a maximum quantum yield of 72%. The tris(phosphine) platinum complexes displayed more red-shifted emissions than the tetrakis complexes. The nature of the emissive excited states is discussed based on the results of density functional theory and time-dependent density-functional theory calculations.","PeriodicalId":9511,"journal":{"name":"Bulletin of the Chemical Society of Japan","volume":null,"pages":null},"PeriodicalIF":4.0,"publicationDate":"2024-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140380710","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The development of quinoidal systems with extended π−conjugation has elucidated the influence that diradical characteristics exert on structure-property relationships, which is significant because it broadens the possibilities for the use of organic semiconducting materials in organic electronics. However, the chain-length elongation of such quinoidal molecules has resulted in low chemical stability due to the large contribution of diradical characteristics and to the high level of the highest occupied molecular orbital (HOMO), both of which limit the synthesis of π−extended quinoidal molecules. Here, we describe solving this problem via aromatic stabilization. To accomplish this, we designed a system that utilizes electron-accepting pyrazine-fused thieno[3,4-b]pyrazine following the development of the isothianaphthene quinoids of thiophene 3-mer and 6-mer. Theoretical calculations indicate that the introduction of a pyrazine-annelated structure suppresses the diradical characteristics and stabilizes the HOMO energy level of quinoidal oligothiophenes. The thermal, photophysical, and physicochemical properties of newly synthesized quinoidal molecules with full annelation of the benzene and pyrazine rings were investigated. Quinoidal thiophene 3-mer functioned as an acceptor in organic solar cells with a power conversion efficiency of 1.04%. This study demonstrates that the introduction of pyrazine-fused rings is an effective molecular design to extend the chain length of quinoidal oligothiophenes.
具有扩展π共轭的类醌体系的开发阐明了二叉特性对结构-性质关系的影响，这一点意义重大，因为它拓宽了有机半导体材料在有机电子学中应用的可能性。然而，由于二叉特性的巨大贡献以及最高占位分子轨道（HOMO）的高水平，这类类醌分子的链长拉长导致化学稳定性较低，这两者都限制了 π 延伸类醌分子的合成。在此，我们介绍通过芳香稳定化来解决这一问题。为了实现这一目标，我们设计了一个系统，该系统利用与噻吩[3,4-b]吡嗪融合的电子接受噻吩[3,4-b]吡嗪，这是继 3-巯基噻吩和 6-巯基噻吩的异噻吩类醌化合物之后的又一发展成果。理论计算表明，引入吡嗪沟道化结构可抑制低聚噻吩的二叉特性并稳定其 HOMO 能级。研究了新合成的苯环和吡嗪环完全环化的醌族分子的热学、光物理和物理化学性质。醌噻吩 3-mer在有机太阳能电池中用作受体，功率转换效率为 1.04%。这项研究表明，引入吡嗪融合环是延长醌基低聚噻吩链长的有效分子设计。
{"title":"Isothianaphthene Quinoids: Pyrazine-Annelated Structures for Tuning Electronic Properties","authors":"Keitaro Yamamoto, Seihou Jinnai, Yutaka Ie","doi":"10.1093/bulcsj/uoae036","DOIUrl":"https://doi.org/10.1093/bulcsj/uoae036","url":null,"abstract":"\u0000 The development of quinoidal systems with extended π−conjugation has elucidated the influence that diradical characteristics exert on structure-property relationships, which is significant because it broadens the possibilities for the use of organic semiconducting materials in organic electronics. However, the chain-length elongation of such quinoidal molecules has resulted in low chemical stability due to the large contribution of diradical characteristics and to the high level of the highest occupied molecular orbital (HOMO), both of which limit the synthesis of π−extended quinoidal molecules. Here, we describe solving this problem via aromatic stabilization. To accomplish this, we designed a system that utilizes electron-accepting pyrazine-fused thieno[3,4-b]pyrazine following the development of the isothianaphthene quinoids of thiophene 3-mer and 6-mer. Theoretical calculations indicate that the introduction of a pyrazine-annelated structure suppresses the diradical characteristics and stabilizes the HOMO energy level of quinoidal oligothiophenes. The thermal, photophysical, and physicochemical properties of newly synthesized quinoidal molecules with full annelation of the benzene and pyrazine rings were investigated. Quinoidal thiophene 3-mer functioned as an acceptor in organic solar cells with a power conversion efficiency of 1.04%. This study demonstrates that the introduction of pyrazine-fused rings is an effective molecular design to extend the chain length of quinoidal oligothiophenes.","PeriodicalId":9511,"journal":{"name":"Bulletin of the Chemical Society of Japan","volume":null,"pages":null},"PeriodicalIF":4.0,"publicationDate":"2024-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140379350","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Shoji Iguchi, Yuki Ikeda, S. Naniwa, Tsunehiro Tanaka, K. Teramura
Photocatalytic conversion of CO2 is a promising technique for realising a carbon neutral society based on the use of renewable energy sources. The application of dual cocatalysts consisting of silver-cobalt or silver-iron significantly improved the photocatalytic activity of an Al−SrTiO3 photocatalyst for the conversion of CO2 to CO in water. In this work, the photocatalytic conversion of CO2 using Ga2O3 and K2YTa5O15 photocatalysts was successfully performed in the presence of a silver-iron dual cocatalyst loaded via a photodeposition method, and both the formation rate of CO and selectivity toward CO production were simultaneously increased by the addition of Fe species. The promotion of the H2O oxidation reaction through Fe addition ensures the superior activity for the CO2 conversion into CO.
光催化转化二氧化碳是实现基于可再生能源的碳中和社会的一项前景广阔的技术。银-钴或银-铁双催化剂的应用大大提高了 Al-SrTiO3 光催化剂在水中将 CO2 转化为 CO 的光催化活性。在这项工作中，通过光沉积方法负载银-铁双助催化剂的情况下，利用 Ga2O3 和 K2YTa5O15 光催化剂成功地实现了 CO2 的光催化转化，并且通过添加铁物种同时提高了 CO 的生成率和 CO 生成的选择性。铁的加入促进了 H2O 氧化反应，确保了 CO2 转化为 CO 的卓越活性。
{"title":"Photocatalytic conversion of CO2 using K2YTa5O15 photocatalyst in the presence of silver-iron dual cocatalyst","authors":"Shoji Iguchi, Yuki Ikeda, S. Naniwa, Tsunehiro Tanaka, K. Teramura","doi":"10.1093/bulcsj/uoae033","DOIUrl":"https://doi.org/10.1093/bulcsj/uoae033","url":null,"abstract":"\u0000 Photocatalytic conversion of CO2 is a promising technique for realising a carbon neutral society based on the use of renewable energy sources. The application of dual cocatalysts consisting of silver-cobalt or silver-iron significantly improved the photocatalytic activity of an Al−SrTiO3 photocatalyst for the conversion of CO2 to CO in water. In this work, the photocatalytic conversion of CO2 using Ga2O3 and K2YTa5O15 photocatalysts was successfully performed in the presence of a silver-iron dual cocatalyst loaded via a photodeposition method, and both the formation rate of CO and selectivity toward CO production were simultaneously increased by the addition of Fe species. The promotion of the H2O oxidation reaction through Fe addition ensures the superior activity for the CO2 conversion into CO.","PeriodicalId":9511,"journal":{"name":"Bulletin of the Chemical Society of Japan","volume":null,"pages":null},"PeriodicalIF":4.0,"publicationDate":"2024-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140237754","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This review focuses on recent advancements regarding mechanoresponsive functions of diacetylene (DA) and polydiacetylene (PDA). Their ability to undergo pronounced topochemical polymerization and chromatic behavior variations in response to external stimuli has marked them as a promising platform for chemo- and bio-sensing over the past few decades. Notably, major advances, showcasing selective and highly sensitive mechanoresponses along with their quantitative analysis, have been achieved in recent years. The categorization includes DAs undergoing pressure-controlled crystalline transitions and polymerization, as well as PDAs exhibiting mechanochromic or mechanofluorochromic transitions. Accordingly, this review covers molecular designs allowing mechanical activation for topochemical polymerization, nanostructured or hybridized PDAs for amplifying stimulus-optical response feedback, nanoscopic analytical tools for mechanochromism, and their potential applications in mechanochemical sensing and imaging.
{"title":"Mechanoresponsive Diacetylenes and Polydiacetylenes: Novel Polymerization and Chromatic Functions","authors":"Yuna Kim, Ken-ichi Iimura, N. Tamaoki","doi":"10.1093/bulcsj/uoae034","DOIUrl":"https://doi.org/10.1093/bulcsj/uoae034","url":null,"abstract":"\u0000 This review focuses on recent advancements regarding mechanoresponsive functions of diacetylene (DA) and polydiacetylene (PDA). Their ability to undergo pronounced topochemical polymerization and chromatic behavior variations in response to external stimuli has marked them as a promising platform for chemo- and bio-sensing over the past few decades. Notably, major advances, showcasing selective and highly sensitive mechanoresponses along with their quantitative analysis, have been achieved in recent years. The categorization includes DAs undergoing pressure-controlled crystalline transitions and polymerization, as well as PDAs exhibiting mechanochromic or mechanofluorochromic transitions. Accordingly, this review covers molecular designs allowing mechanical activation for topochemical polymerization, nanostructured or hybridized PDAs for amplifying stimulus-optical response feedback, nanoscopic analytical tools for mechanochromism, and their potential applications in mechanochemical sensing and imaging.","PeriodicalId":9511,"journal":{"name":"Bulletin of the Chemical Society of Japan","volume":null,"pages":null},"PeriodicalIF":4.0,"publicationDate":"2024-03-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140244945","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
To further explore the π-conjugated systems of anthracene bisimide (ABI) and investigate their electronic properties, we synthesized donor–acceptor linear arrays. These arrays consist of an ABI unit as the acceptor and a 9,10-anthrylene unit as the donor, linked by a butadiynylene spacer. We constructed these donor–acceptor arrays through Hay coupling of the corresponding 9,10-diethynylABI derivative with a 9,10-diethynylanthracene derivative. Theoretical calculations and electronic spectra analysis were employed to compare the photophysical properties of these compounds with those of their acetylene analogs. Moreover, we evaluated the intramolecular electronic interactions between the ABI and anthrylene units, focusing on the effects of the butadiynylene spacer and array sequences.
为了进一步探索蒽二亚胺（ABI）的π-共轭体系并研究其电子特性，我们合成了供体-受体线性阵列。这些阵列由作为受体的 ABI 单元和作为供体的 9,10-蒽单元组成，并由丁二烯间隔物连接。我们通过将相应的 9,10-二乙炔基ABI 衍生物与 9,10-二乙炔基蒽衍生物进行干草耦合，构建了这些供体-受体阵列。通过理论计算和电子光谱分析，我们将这些化合物的光物理特性与其炔类似物的光物理特性进行了比较。此外，我们还评估了 ABI 和蒽单元之间的分子内电子相互作用，重点研究了丁二烯间隔和阵列序列的影响。
{"title":"Synthesis and Electronic Properties of Donor–Acceptor Linear Arrays Comprising Anthracene Bisimide with Butadiynylene Spacers","authors":"Tetsuo Iwanaga, Keisuke Tanaka, Kento Kawano","doi":"10.1093/bulcsj/uoae031","DOIUrl":"https://doi.org/10.1093/bulcsj/uoae031","url":null,"abstract":"\u0000 To further explore the π-conjugated systems of anthracene bisimide (ABI) and investigate their electronic properties, we synthesized donor–acceptor linear arrays. These arrays consist of an ABI unit as the acceptor and a 9,10-anthrylene unit as the donor, linked by a butadiynylene spacer. We constructed these donor–acceptor arrays through Hay coupling of the corresponding 9,10-diethynylABI derivative with a 9,10-diethynylanthracene derivative. Theoretical calculations and electronic spectra analysis were employed to compare the photophysical properties of these compounds with those of their acetylene analogs. Moreover, we evaluated the intramolecular electronic interactions between the ABI and anthrylene units, focusing on the effects of the butadiynylene spacer and array sequences.","PeriodicalId":9511,"journal":{"name":"Bulletin of the Chemical Society of Japan","volume":null,"pages":null},"PeriodicalIF":4.0,"publicationDate":"2024-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140251921","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Recently, the supramolecular polymerization of chlorophyll pigments mimicking a natural light-harvesting apparatus (chlorosome) was demonstrated in low-polar organic solvents or aqueous solutions. To obtain the most aggregation models, a concentrated solution of the pigments in a polar organic solvent was diluted with a large amount of a nonpolar organic solvent or water. Here, bacteriochlorophyll-d analogs possessing different-length branched alkyl chains at the peripheral 17-propionate residue on the core chlorin π-system were prepared, and their well-soluble chlorosomal supramolecules were produced in single 1-chlorooctane as a low-polar solvent. Temperature-dependent electronic absorption and circular dichroism spectroscopies were employed to analyze their self-aggregation and disaggregation mechanisms. The synthetic analogs were monomeric at high temperatures and self-aggregated during cooling of the hot solution through a non-sigmoidal pathway. The obtained chlorosomal self-aggregates were reversibly monomerized by heating the homogeneous solution. The disaggregation pathway was fitted to an isodesmic model whose melting points depended on the alkyl-chain lengths.
{"title":"Temperature-dependent chlorosomal self-aggregation of bacteriochlorophyll-d analogs with a branched alkyl chain in a single 1-chlorooctane solvent","authors":"Nobuyuki Hara, Hitoshi Tamiaki","doi":"10.1093/bulcsj/uoae032","DOIUrl":"https://doi.org/10.1093/bulcsj/uoae032","url":null,"abstract":"\u0000 Recently, the supramolecular polymerization of chlorophyll pigments mimicking a natural light-harvesting apparatus (chlorosome) was demonstrated in low-polar organic solvents or aqueous solutions. To obtain the most aggregation models, a concentrated solution of the pigments in a polar organic solvent was diluted with a large amount of a nonpolar organic solvent or water. Here, bacteriochlorophyll-d analogs possessing different-length branched alkyl chains at the peripheral 17-propionate residue on the core chlorin π-system were prepared, and their well-soluble chlorosomal supramolecules were produced in single 1-chlorooctane as a low-polar solvent. Temperature-dependent electronic absorption and circular dichroism spectroscopies were employed to analyze their self-aggregation and disaggregation mechanisms. The synthetic analogs were monomeric at high temperatures and self-aggregated during cooling of the hot solution through a non-sigmoidal pathway. The obtained chlorosomal self-aggregates were reversibly monomerized by heating the homogeneous solution. The disaggregation pathway was fitted to an isodesmic model whose melting points depended on the alkyl-chain lengths.","PeriodicalId":9511,"journal":{"name":"Bulletin of the Chemical Society of Japan","volume":null,"pages":null},"PeriodicalIF":4.0,"publicationDate":"2024-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140253728","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Precisely defined deuterium labeling of simplified Maruoka Catalyst® markedly increases its robustness under basic conditions, but the reason for this has remained unclear. Based on MC_DFT calculations, we find that an inverse kinetic isotope effect in singlet-to-triplet intersystem crossing contributes to the greater robustness of the deuterated catalyst.
{"title":"Inverse Kinetic Isotope Effect in Singlet-to-Triplet Intersystem Crossing Contributes to Greater Robustness of Deuterated Organocatalyst","authors":"Seiishiro Murayama, Takayoshi Ishimoto, Hiroshi Naka","doi":"10.1093/bulcsj/uoae028","DOIUrl":"https://doi.org/10.1093/bulcsj/uoae028","url":null,"abstract":"\u0000 Precisely defined deuterium labeling of simplified Maruoka Catalyst® markedly increases its robustness under basic conditions, but the reason for this has remained unclear. Based on MC_DFT calculations, we find that an inverse kinetic isotope effect in singlet-to-triplet intersystem crossing contributes to the greater robustness of the deuterated catalyst.","PeriodicalId":9511,"journal":{"name":"Bulletin of the Chemical Society of Japan","volume":null,"pages":null},"PeriodicalIF":4.0,"publicationDate":"2024-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140077447","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Takashi Miura, T. R. Malla, L. Brewitz, A. Tumber, E. Salah, Kang Ju Lee, Naohiro Terasaka, C. Owen, C. Strain-Damerell, P. Lukacik, M. Walsh, A. Kawamura, Christopher J. Schofield, T. Katoh, H. Suga
Due to their constrained conformations, cyclic β2,3-amino acids (cβAA) are key building blocks that can fold peptides into compact and rigid structures, improving peptidase resistance and binding affinity to target proteins, due to their constrained conformations. Although the translation efficiency of cβAAs is generally low, our engineered tRNA, referred to as tRNAPro1E2, enabled efficient incorporation of cβAAs into peptide libraries using the flexible in vitro translation (FIT) system. Here we report on the design and application of a macrocyclic peptide library incorporating three kinds of cβAAs: (1R,2S)-2-aminocyclopentane carboxylic acid (β1), (1S,2S)-2-aminocyclohexane carboxylic acid (β2), and (1R,2R)-2-aminocyclopentane carboxylic acid. This library was applied to an in vitro selection against the SARS-CoV-2 main protease (Mpro). The resultant peptides, BM3 and BM7, bearing one β2 and two β1, exhibited potent inhibitory activities with IC50 values of 40 nM and 20 nM, respectively. BM3 and BM7 also showed remarkable serum stability with half-lives of 48 h and >168 h, respectively. Notably, BM3A and BM7A, wherein the cβAAs were substituted with alanine, lost their inhibitory activities against Mpro and displayed substantially shorter serum half-lives. This observation underscores the significant contribution of cβAA to the activity and stability of peptides. Overall, our results highlight the potential of cβAA in generating potent and highly stable macrocyclic peptides with drug-like properties.
{"title":"Cyclic β2,3-amino acids improve the serum stability of macrocyclic peptide inhibitors targeting the SARS-CoV-2 main protease","authors":"Takashi Miura, T. R. Malla, L. Brewitz, A. Tumber, E. Salah, Kang Ju Lee, Naohiro Terasaka, C. Owen, C. Strain-Damerell, P. Lukacik, M. Walsh, A. Kawamura, Christopher J. Schofield, T. Katoh, H. Suga","doi":"10.1093/bulcsj/uoae018","DOIUrl":"https://doi.org/10.1093/bulcsj/uoae018","url":null,"abstract":"\u0000 Due to their constrained conformations, cyclic β2,3-amino acids (cβAA) are key building blocks that can fold peptides into compact and rigid structures, improving peptidase resistance and binding affinity to target proteins, due to their constrained conformations. Although the translation efficiency of cβAAs is generally low, our engineered tRNA, referred to as tRNAPro1E2, enabled efficient incorporation of cβAAs into peptide libraries using the flexible in vitro translation (FIT) system. Here we report on the design and application of a macrocyclic peptide library incorporating three kinds of cβAAs: (1R,2S)-2-aminocyclopentane carboxylic acid (β1), (1S,2S)-2-aminocyclohexane carboxylic acid (β2), and (1R,2R)-2-aminocyclopentane carboxylic acid. This library was applied to an in vitro selection against the SARS-CoV-2 main protease (Mpro). The resultant peptides, BM3 and BM7, bearing one β2 and two β1, exhibited potent inhibitory activities with IC50 values of 40 nM and 20 nM, respectively. BM3 and BM7 also showed remarkable serum stability with half-lives of 48 h and >168 h, respectively. Notably, BM3A and BM7A, wherein the cβAAs were substituted with alanine, lost their inhibitory activities against Mpro and displayed substantially shorter serum half-lives. This observation underscores the significant contribution of cβAA to the activity and stability of peptides. Overall, our results highlight the potential of cβAA in generating potent and highly stable macrocyclic peptides with drug-like properties.","PeriodicalId":9511,"journal":{"name":"Bulletin of the Chemical Society of Japan","volume":null,"pages":null},"PeriodicalIF":4.0,"publicationDate":"2024-03-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140077958","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Efforts made over the past three decades have led to the development of various organic transformations that directly convert unfunctionalized C–H bonds into functional groups by metal catalysis. However, many of these transformations are restricted to specific reaction sites controlled by directing groups, which bring the metal centers into proximity with the C–H bonds being functionalized. These directing groups are typically tailored for specific C–H functionalization reactions, necessitating additional steps for their installation and removal, thereby limiting overall utility and efficiency. There is a strong desire to achieve site-selectivity control using catalysts with compounds bearing common functional groups. We have investigated catalytic Lewis-pair formations to electronically activate substrates and control the site-selectivity of metal-catalyzed arene C–H functionalization. In this account, we present C–C and C–B bond-forming reactions through cooperative transition metal/Lewis acid (LA) catalysis. Common Lewis acid catalysts derived from Zn, B, and Al have been demonstrated as highly efficient co-catalysts for Ni- and Ir-catalyzed arene C–H functionalization. Steric repulsion between the LA and Ni or Ir catalysts facilitates para-selective C–H functionalization, while ligands bearing such Lewis acid moieties effectively control meta-selectivity.
{"title":"Site-selective Arene C–H Functionalization by Cooperative Metal Catalysis","authors":"Yoshiaki Nakao","doi":"10.1093/bulcsj/uoae027","DOIUrl":"https://doi.org/10.1093/bulcsj/uoae027","url":null,"abstract":"\u0000 Efforts made over the past three decades have led to the development of various organic transformations that directly convert unfunctionalized C–H bonds into functional groups by metal catalysis. However, many of these transformations are restricted to specific reaction sites controlled by directing groups, which bring the metal centers into proximity with the C–H bonds being functionalized. These directing groups are typically tailored for specific C–H functionalization reactions, necessitating additional steps for their installation and removal, thereby limiting overall utility and efficiency. There is a strong desire to achieve site-selectivity control using catalysts with compounds bearing common functional groups. We have investigated catalytic Lewis-pair formations to electronically activate substrates and control the site-selectivity of metal-catalyzed arene C–H functionalization. In this account, we present C–C and C–B bond-forming reactions through cooperative transition metal/Lewis acid (LA) catalysis. Common Lewis acid catalysts derived from Zn, B, and Al have been demonstrated as highly efficient co-catalysts for Ni- and Ir-catalyzed arene C–H functionalization. Steric repulsion between the LA and Ni or Ir catalysts facilitates para-selective C–H functionalization, while ligands bearing such Lewis acid moieties effectively control meta-selectivity.","PeriodicalId":9511,"journal":{"name":"Bulletin of the Chemical Society of Japan","volume":null,"pages":null},"PeriodicalIF":4.0,"publicationDate":"2024-03-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140264222","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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