Search

The ammonia affinity can precisely evaluate the Lewis acidity of organoboronic acid derivatives including boronamides and boronates.

An electron-deficient triarylphosphine-coordinated Pt-catalyzed diboration of terminal alkynes with (pin)B–B(aam) provides vic-diborylalkenes, whose difference in the boron-Lewis acidities allows chemoselective cross-coupling to proceed sequentially.

Various naphthalene-1,8-diaminato (dan)-substituted organo- and silyl-boron compounds can directly be synthesized under transition metal-free conditions.

Surface ligands play a critical role in the synthesis of metal nanoclusters (NCs) tuning the sizes, compositions, structures, and properties at the atomic level. Chiral ligands often lead to the fo...

Migita–Kosugi–Stille coupling (MKSC) of arylstannanes has proven to be one of the most reliable methods that can be used for constructing various carbon frameworks of organic compounds, being otherwise difficult to be obtained. Cocatalysis of a copper salt is well established in MKSC; however, electronic and structural factors affecting the transmetalation between arylstannanes and a copper salt have scarcely been explored. Herein, we disclose that arylstannanes with high tin-Lewis acidity, high nucleophilicity, or a directing group are apt to undergo transmetalation with a copper salt. The tendency in the transmetalation has been applied to Pd/Cu-cocatalyzed site-selective MKSC by use of perfluoroaryl- and heteroaryl-stannanes, where the transmetalation-active SnBu3 moieties can exclusively be coupled with aryl halides, leaving other SnBu3 moieties intact. Furthermore, tin-Lewis acidity of various arylstannanes, one of the major factors determining the transmetalation activity, can be quantitatively estimated by correlating experimental data (119Sn NMR chemical shifts) with various computed values (fluoride ion affinity, LUMO energy level, global electrophilicity index).

Theoretical calculation-based ammonia affinity (AA) has been found to unifiedly evaluate Lewis acidity of organoboronic acid derivatives [boronates: B(pin), B(neop), B(cat), B(eg), B(nad); boronamides: B(dan), B(aam), B(mdan)], while other methods [LUMO energies, global electrophilicity index (GEI), fluoride ion affinity (FIA)] were only partially applicable. The AA analysis estimated that the Lewis acidity of the B(mdan) moiety was sufficiently diminished but stronger than the B(dan) moiety; this was experimentally demonstrated by excellent stability toward hydrolysis and direct cross-coupling with a weak base.

We herein describe the direct Suzuki–Miyaura coupling of dan-substituted, saturated organoboron compounds. Despite its Lewis acidity-diminished and robust character of the boron center, cyclopropyl–B(dan) can be activated by t-BuOK to under-go transmetalation with a palladium complex. The increased s-character of the C–B(dan) bond as compared with other alkyl–B(dan) should be the key to the smooth reaction.

A B(dan) moiety (dan=naphthalene-1,8-diaminato) of diminished boron-Lewis acidity has efficiently been installed into organic frameworks by three-component carboboration of alkenes under copper catalysis, where a Cu-B(dan) species, generated by chemoselective σ-bond metathesis between a copper catalyst and an unsymmetrical diboron [(pin)B-B(dan)], acts as a key intermediate. The Cu-B(dan) species has also turned out to serve as a B(dan) nucleophile to afford various dan-substituted organoboranes via borylative substitution of carbon electrophiles. Furthermore, borylation reactions with another Lewis acidity-diminished boron unit, B(aam) (aam=anthranilamidato), have become feasible by use of (pin)B-B(aam) or H-B(aam). The resulting dan/aam-substituted organoboranes have been demonstrated to undergo direct cross-coupling without prior acidic deprotection, regardless of their diminished boron-Lewis acidity. Synthesis of diverse organostannanes based upon copper-catalyzed carbostannylation and borylstannylation, in which Lewis acidity increment of a tin center facilitates the progress in some cases, have also been described.

Giant cell arteritis (GCA) and Takayasu arteritis (TAK) are two types of primary large vessel vasculitis (LVV). LVV is an intractable, rare disease with a high relapse rate. Disease progression in asymptomatic patients is an important issue in the clinical management of LVV. Useful biomarkers associated with clinical phenotypes, disease activity, and prognosis may be present in peripheral blood. In this review, we focused on peripheral leukocyte counts, surface markers, functions, and gene expression in LVV patients. In particular, we explored longitudinal changes in circulating immune cell phenotypes during the active phase of the disease and during treatment. The numbers and phenotypes of leukocytes in the peripheral blood were different between LVV and healthy controls, GCA and TAK, LVV in active versus treatment phases, and LVV in treatment responders versus non-responders. Therefore, biomarkers obtained from peripheral blood immune cells may be useful for longitudinal monitoring of disease activity in LVV.

Imparting chirality affords additive values, functions and responsiveness in molecular systems including nanoscale materials. Here, we report pathway-dependent chirality control in silver nanoclusters (NCs). The use of enantiomeric ligand, α-dihydrolipoic acid (DHLA), for the synthesis of Ag NCs leads to the preferential formation of one-handed chiral Ag

Sulfonium salts and sulfur ylides are important S(IV) motifs, and have displayed many unique reactivities to provide simple, effective, and often stereoselective synthesis toward sulfur containing compounds. Impressive developments have been witnessed within this field during the past several years. In light of the increasing demand of organosulfur compounds across the range of chemical sciences, our aim of this review is to provide a concise overview of recent advances of sulfonium salt and sulfur ylide chemistry. Selected examples are organized in three parts on the basis of their role in organic reactions (reactants, intermediates and catalysts).

A highly stable, air-resistant silylborane containing a PhMe2Si moiety, whose boron Lewis acidity was diminished, was synthesized.

Chiral surface ligands have often been employed to impart optical activity to metal nanoclusters, metal nanoparticles and semiconductor nanocrystals. They are considered to form a chiral structure to a certain degree whereas the effect of such chiral structure on the global physicochemical properties apart from chiroptical ones has been unexplored. We herein demonstrate the impact of optical purity of chiral surface ligand on the emission property of silver nanocluster (NCs). Chiral bidentate α-dihydrolipoic acid (DHLA) with varied enantiomeric excess (ee) values was employed as a surface capping ligand to prepare a series of silver NCs, displaying identical absorption and emission profiles typical for Ag29 NCs. Interestingly, the emission quantum yields exhibited a clear dependence on the enantiopurity of DHLA. The more enantiopure DHLA afforded more emissive NCs. This |ee|-dependent emission efficiency was discussed in association with the orientation of ligands on the Ag29 NCs. The surface structures of Ag29(dithiolate)12 models composed of enantiopure and racemic ligand systems were compared with the aid of DFT calculations, suggesting that the enantiopure surface is more stable with one-handed ligand orientation. Two-dimensional NMR technique also supported the observation that well-defined ligand orientations depend on the enantiomeric composition of chiral ligand.

Dithiazolylthienothiophene bisimide (TzBI) is a promising building unit for donor-acceptor π-conjugated polymers due to its strong electron-deficiency and high coplanarity. We previously reported a...

The optical activity of a metal nanocluster (NC) is induced either by an asymmetric arrangement of constituents or by a dissymmetric field of a chiral ligand layer. Herein, we unveil the origin of chirality in Ag29 NCs, which is attributed to the intrinsically chiral atomic arrangement. The X-ray crystal structure of a Ag29(BDT)12(TPP)4 NC (BDT: 1,3-benzenedithiol; TPP: triphenylphosphine) manifested the presence of intrinsic chirality in the outer shell capping the icosahedral achiral Ag13 core. The enantiomers of the Ag29(BDT)12(TPP)4 NC are separated by high-performance liquid chromatography (HPLC) using a chiral column for the first time, showing mirror-image circular dichroism (CD) spectra. The CD spectra are reproduced by time-dependent density functional theory (TDDFT) calculations based on enantiomeric Ag29 models with achiral 1,3-propanedithiolate ligands. The mechanism of chiral induction in the synthesis of Ag29(DHLA)12 (DHLA: α-dihydrolipoic acid) NCs with a chiral ligand system is further discussed with the aid of DFT calculations. The use of the enantiomeric DHLA ligand preferentially leads to a one-handed atomic arrangement which is more stable than the opposite one, inducing the enantiomeric excess in the population of intrinsically chiral Ag29 NCs with CD activity.

H-B(dan) was demonstrated to serve as a B(dan) electrophile, despite its highly diminished boron-Lewis acidity, leading to direct and transition metal-free approach to R-B(dan) of high synthetic utility upon treatment with Grignard reagents. Iterative cross-coupling of 5-bromo-2-pyridyl-B(dan), synthesized by the present method, was also achieved.

Ozasa R., Matsugaki A., Ishimoto T., et al. Bone fragility via degradation of bone quality featured by collagen/apatite micro-arrangement in human rheumatic arthritis. Bone, 155, 116261. https://doi.org/10.1016/j.bone.2021.116261., Although increased bone fragility is a well-recognized consequence in patients with rheumatoid arthritis (RA), the essential cause of degenerate bone strength remains unknown. This study aimed to determine factors contributing to bone dysfunction in RA by focusing on the bone matrix micro-arrangement, based on the preferential orientation of collagen and the related apatite c-axis as a bone quality index. The classical understanding of RA is limited to its severe pathological conditions associated with inflammation-induced bone loss. This study examined periarticular proximal tibiae from RA patients as compared with osteoarthritis (OA) patients as controls. Bone tissue material strength was disrupted in the RA group compared with the control. Collagen/apatite micro-arrangement and vBMD were significantly lower in the RA group, and the rate of decrease in apatite c-axis orientation (−45%) was larger than that in vBMD (−22%). Multiple regression analysis showed that the degree of apatite c-axis orientation (β = 0.52, p = 1.9 × 10−2) significantly contributed to RA-induced bone material impairment as well as vBMD (β = 0.46, p = 3.8 × 10−2). To the best of our knowledge, this is the first report to demonstrate that RA reduces bone material strength by deteriorating the micro-arrangement of collagen/apatite bone matrix, leading to decreased fracture resistance. Our findings represent the significance of bone quality-based analysis for precise evaluation and subsequent therapy of the integrity and soundness of the bone in patients with RA.

”Copper effect” in Migita–Kosugi–Stille coupling (MKSC) has been well known as acceleration effect by a copper cocatalyst, which has thus far been ascribed to two different actions of copper depending on polarity of solvents, i.e., Sn/Cu transmetalation (in polar solvent such as DMF and NMP) and scavenging of ligands (in less polar ethereal solvent). Herein, we report on reconsideration of the copper effect; MKSC is markedly accelerated based on the Sn/Cu transmetalation in ethereal solvents. In particular, perfluorophenyl- and heteroaryl-stannanes were found to undergo the Sn/Cu transmetalation with excellent site-selectivity in the presence of other Ar–Sn bonds under the ethereal conditions, leading to highly chemoselective, sequential MKSC without masking/unmasking process on a tin center. Moreover, we have also demonstrated that a combination of 119Sn NMR chemical shifts (experimental) and computed FIA (theoretical) provides a quantitative criterion estimating tin-Lewis acidity that is strongly linked to activity toward the present MKSC.

Trialkylsilyl lithium species have turned out to be facilely generated by treating hexaalkyl disilanes with methyl lithium in the presence of tris(N,N-tetramethylene)phosphoric triamide (TPPA) as an activator, which can be trapped by boron electrophiles to afford silylboronic esters including long-awaited Me3Si–B(pin).

The optical activity of a metal nanocluster (NC) is induced either by an asymmetric arrangement of constituents or by a dissymmetric field of a chiral ligand layer. Herein, we unveil the origin of chirality in Ag29 NCs, which is attributed to the intrinsically chiral atomic arrangement. The X-ray crystal structure of a Ag29(BDT)12(TPP)4 NC (BDT: 1,3-benzenedithiol; TPP: triphenylphosphine) manifested the presence of intrinsic chirality in the outer shell capping the icosahedral achiral Ag13 core. The enantiomers of the Ag29(BDT)12(TPP)4 NC are separated by high-performance liquid chromatography (HPLC) using a chiral column for the first time, showing mirror-image circular dichroism (CD) spectra. The CD spectra are reproduced by time-dependent density functional theory (TDDFT) calculations based on enantiomeric Ag29 models with achiral 1,3-propanedithiolate ligands. The mechanism of chiral induction in the synthesis of Ag29(DHLA)12 (DHLA: α-dihydrolipoic acid) NCs with a chiral ligand system is further discussed with the aid of DFT calculations. The use of the enantiomeric DHLA ligand preferentially leads to a one-handed atomic arrangement which is more stable than the opposite one, inducing the enantiomeric excess in the population of intrinsically chiral Ag29 NCs with CD activity., Enantioseparation of Ag29 nanoclusters with intrinsic chirality was performed by chiral HPLC, affording a pair of fractions with mirror image CD spectra.

Installation of a boron functionality into a more substituted carbon of terminal alkynes has been a challenging issue in chemical synthesis, since inherently Lewis acidic boron moieties, in principle, favor their attachment to a terminal carbon. Herein, we report on the highly internal-selective borylation of terminal alkynes under copper catalysis, wherein diminishment of boron-Lewis acidity and ligand-derived steric bulk around a copper center are the key to the success. In particular, the use of an anthranilamide-substituted boron moiety [B(aam)] is of high synthetic significance, because its properly diminished Lewis acidity enabled the internal regioselectivity and the Suzuki–Miyaura cross-coupling activity to be compatibly achieved. This method provided direct and universal approach to variously substituted branched alkenylboron compounds, regardless of electronic and steric properties of a substituent on terminal alkynes.

N-type (electron-transporting) semiconducting polymers are essential materials for the development of truly plastic electronic devices. Here, we synthesized for the first time dithiazolylthienothiophene bisimide (TzBI), as a new family for imide-based electron-deficient π-conjugated systems, and semiconducting polymers by incorporating TzBI into the π-conjugated backbone as the building unit. The TzBI-based polymers are found to have deep frontier molecular orbital energy levels and wide optical bandgaps compared to the dithienylthienothiophene bisimide (TBI) counterpart. It is also found that TzBI can promote the π–π intermolecular interactions of the polymer backbones relative to TBI most probably because the thiazole ring, which replaced the thiophene ring, at the end of the framework gives a more coplanar backbone. In fact, TzBI-based polymers function as the n-type semiconducting material in both organic field-effect transistor (OFET) and organic photovoltaic (OPV) devices. Notably, one of the TzBI-based polymers provides a power conversion efficiency of 3.3% in the all-polymer OPV device, which could be high for a low-molecular-weight polymer (

Aim Perceived health status, including physical and cognitive fitness, will be negatively associated with future health conditions among old-old adults. The coronavirus disease 2019 (COVID-19) pandemic has caused sudden changes in lifestyle. Thus, this study examined the associations of participation in an exercise class before the COVID-19 pandemic and the exercise habits and disruption to the rhythms of daily life during the COVID-19 state of emergency with perceived declining physical and cognitive fitness among community-dwelling old-old adults. Methods In July 2020, we carried out a mail survey of community-dwelling old-old adults aged between 77 and 99 years in Bibai, Hokkaido, Japan, to determine their perceived declining physical and cognitive fitness during the COVID-19 state of emergency. Results Of the 774 responders, 339 (43.8%) participants reported a decline in physical fitness, whereas 259 (33.5%) perceived declining cognitive fitness during the COVID-19 state of emergency. In a multivariate logistic regression model adjusted for potential confounders, exercise habits during the COVID-19 state of emergency were significantly associated with a lower perception of declining physical fitness. Disruption to the rhythms of daily life during the COVID-19 state of emergency was significantly associated with a higher perception of declining physical and cognitive fitness. Conclusions Approximately half and more than one-third of community-dwelling old-old adults perceived declining physical and cognitive fitness, respectively, during the COVID-19 state of emergency. During this period, exercise habits were positively correlated with perceived health status among old-old adults, whereas disruption to the rhythms of daily life was negatively correlated. Geriatr Gerontol Int 2021; ••: ••-••.

Objectives Large vessel vasculitis (LVV) is characterised by a high relapse rate. Because accurate assessment of the LVV disease status can be difficult, an accurate prognostic marker for initial risk stratification is required. We conducted a comprehensive longitudinal investigation of next‐generation RNA‐sequencing data for patients with LVV to explore useful biomarkers associated with clinical characteristics. Methods Key molecular pathways relevant to LVV pathogenesis were identified by examining the whole blood RNA from patients with LVV and healthy controls (HCs). The data were examined by pathway analysis and weighted gene correlation network analysis (WGCNA) to identify functional gene sets that were differentially expressed between LVV patients and HCs, and associated with clinical features. We then compared the expression of the selected genes during week 0, week 6, remission and relapse. Results The whole‐transcriptome gene expression data for 108 samples obtained from LVV patients (n = 27) and HCs (n = 12) were compared. The pathway analysis and WGCNA revealed that molecular pathway related to interleukin (IL)‐1 was significantly upregulated in LVV patients compared with HCs, which correlated with the positron emission tomography vascular activity score, a disease‐extent score based on the distribution of affected arteries. Further analysis revealed that the expression levels of genes in the IL‐1 signalling pathway remained high after conventional treatment and were associated with disease relapse. Conclusion Upregulation of the IL‐1 signalling pathway was a characteristic of LVV patients and was associated with the extent of disease and a poor prognosis., In this study, we found that interleukin (IL)‐1 signalling was upregulated in large vessel vasculitis (LVV) and correlated with the disease‐extent score. IL‐1 signalling remained upregulated even after conventional treatment and was associated with disease relapse. Targeting IL‐1 signalling may be a promising therapeutic approach for LVV.

Arynes have been demonstrated to be sequentially inserted into an F–Sn bond of a tin fluoride and a C(aryl)–Sn bond of 2-fluoroarylstannanes generated therefrom. This one-pot fluorostannylation–ary...

Rheumatoid arthritis (RA) is a common inflammatory form of arthritis leading to the progressive bone and joint destruction. Many factors are closely involved in the pathology of RA, in particular bone-related cells and inflammatory cytokines such as TNF-α and interleukin-6 (IL-6). Because RA patients with progressive bone destruction experience accelerated deterioration of their quality of life, inhibition of disease progression and joint destruction has become an important clinical goal. Recent studies have also found that drug intervention targeting proinflammatory cytokines such as IL-6 results in bone repair in addition to suppression of bone and joint destruction, and these results suggest the potential for new therapeutic goals. Regarding the relationship between IL-6 and bone destruction, essential roles of osteoclasts have been reported over many years; however, more recent studies have explored the relationship of IL-6 with osteoblasts and osteocytes. In this review, we highlight the perspectives of basic and clinical research, adding new findings on the relationships between IL-6 and bone-related cells associated with inflammation, and the possibility of bone repair by blocking IL-6.

Trialkylsilyllithium species have turned out to be facilely generated by treating hexaalkyldisilanes with methyllithium in the presence of tris(N,N-tetramethylene)phosphoric triamide (TPPA) as an activator, which can be trapped by boron electrophiles to afford silylboronic esters including long-awaited Me3Si–B(pin).

Unsymmetrical B(MIDA)-containing diborons of potential synthetic utility were found to be synthesized from the readily available (neop)B–B(neop) and (HO)2B–B(OH)2, and the procedure was extended to the generation of symmetrical (MIDA)B–B(MIDA). NMR and X-ray crystal structure studies revealed that B(MIDA) units of all of the diborons obtained in this study were in rigid tetrahedral environment., This work was financially supported by JSPS KAKENHI Grant Numbers JP16H01031 in Precisely Designed Catalysts with Customized Scaffolding and JP17K05864.

Naphthobispyrazine (NPz), a family of naphthalene-based electron-deficient fused heteroaromatic rings, and its derivatives including a polymer are efficiently synthesized via the ring-opening reaction of corresponding naphthobisthiadiazole derivatives. The electrochemical and optical measurements of the NPz-based molecules and polymers revealed that NPz has relatively weak electron deficiency and thus affords medium band-gap polymers. The photovoltaic properties of the polymer, in combination with PC61BM, were also studied.