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This study reports the formation of low-molecular-weight gelators based on carboxylic acids derived from chiral cyclic -β-amino acids. The effect of their stereochemistry on the gelation of organic solvents was investigated, and their assemblies with the intermolecular interactions in the xerogels were proposed via infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and crystallographic details of the related model compounds. The effect of the alkyl chain length on the gelators was studied, and they were applied to the chiral recognition of amines. Only one diastereomeric salt with amines afforded gels, whereas the others resulted in precipitates. Chiral recognition was also achieved in the gel state, and the appearance of the as-prepared gel changed upon the addition of each amine enantiomer, thus enabling the visual detection of their chirality.

Chiral amphiphiles are useful for controlling the structures and properties of supramolecular assemblies, but their stereocontrolled synthesis is generally difficult, because their long alkyl chains tend to bring unfavorable effects on the solubility, reactivity, and crystallinity of molecules. Typical examples are amphiphilic 1,2-amino alcohols (S)-1 and (1S,2S)-2 developed by our group, which were known to serve as chiral reaction media for controlling the stereochemistry of asymmetric photoreactions. We previously developed synthetic schemes for these 1,2-amino alcohols, but their synthetic efficiencies were unsatisfactory (13 steps with 2% overall yield for (S)-1; eight steps with 8% yield for (1S,2S)-2). As the main reason of such low efficiencies, the stereocontrolling methods we previously employed (diastereomer-salt crystallization for (S)-1; stereoselective reactions for (1S,2S)-2) were not ideal. Here, we report highly improved synthetic schemes for (S)-1 and (1S,2S)-2 based on the enantioselective high performance liquid chromatography (HPLC) separation of intermediates in preparative scales. Compared with the previous schemes, the new schemes are advantageous in fewer number of steps, higher overall yield, and lower risk of racemization (seven steps with 15% overall yield for (S)-1; seven steps with 26% overall yield for (1S,2S)-2).

We synthesized a polythiophene derivative containing a photocleavable coumarin unit in the side chain. The resulting polymer contained 56% coumarin units with a number-average molecular weight of 17,000. When a film of the polythiophene derivative was irradiated at 313 nm, 54% of the coumarin groups were photocleaved. Fourier transform infrared spectroscopy revealed that the photocleaved side chains were transformed to carboxyl groups. Formation of the carboxyl group changed the nature of the surface of the polymer film from hydrophobic to hydrophilic. Furthermore, photocleavage of the coumarin unit changed the solubility of the polymer in organic solvents. Taking advantage of this solubility change, we photopatterned the polythiophene film using a photomask. In addition, the photocleaved polythiophene film showed a 104-fold increase in electrical conductivity after chemical doping. We report a photoresponsive polythiophene derivative containing a photocleavable coumarin group with an octyloxy side chain as a solubilizing group. This polymer enables fabrication of solution-processed polymer film owing to the solubilizing group. Photoirradiation at 313 nm gives the photocleaved side chain, yielding a carboxyl group. Formation of the carboxyl group causes insoluble polythiophene. Change in the solubility provides a photopatterned film through a photomask. In addition, the photocleaved polythiophene film exhibits a 104-fold increase in the electrical conductivity by chemical doping.

The photocyclodimerization of 2-anthracenecarboxylic acid has been extensively studied as a model reaction of asymmetric photochemistry. So far, numerous chiral environments have been employed to control this photoreaction, while the scope of photoreactants has been limited only to 2-anthracenecarboxylic acid and its simple esters and amides. Here, we developed a systematic series of photoreactants (2 a-d) by introducing various substituents to 2-anthracenecarboxylic acid, which showed different reactivities and selectivities depending on the substituents. By using the photoreactants 2 a-d, we evaluated the performance of a chiral environment composed of an amphiphilic amino alcohol (1), where the photocyclodimerization of 2 a-d generally proceeded in excellent regio- and enantioselectivities (71-98 % regio ratio, 76-86 % ee). Furthermore, by reacting 2 a and 2 b together in the chiral environment of 1, we succeeded in the first stereocontrolled cross-photocyclodimerization between two prochiral anthracenes (58 % chemo ratio, 83 % regio ratio, 90 % ee).

Seven N2- and N3-ligands (L1–L7) were developed for the ligand-assisted CuI-catalyzed coupling reactions of aryl halides with phenols. The structural and electronic effects were studied for various combinations of pyridine and/or imine nitrogen binding sites in the ligands. 2-(1-Pyrazolyl)pyridine (L1) featuring two types of binding sites gave the best results, with yields of up to 90% at 100 °C at a catalyst loading of 10 mol% (CuI/L in 1:1 ratio). A non-radical mechanism, proposed for the L1-promoted coupling reaction, well explained the different effects of electronic nature of the substituent and steric hindrance on phenols and aryl halides.

The solvent effect on the enantioseparation of halogen-substituted mandelic acid derivatives via diastereomeric salt formation has been investigated. The diastereomeric salts of para-halogen-substi...

Amidine-based optically active resolving agents for enantiomer separation of axially chiral 1,1′-biaryl-2,2′-diols have been developed. A strongly basic amidine bearing no substituents on its nitrogen atoms enables the formation of their diastereomeric salts upon being mixed with weakly acidic phenol derivatives. Enantiopure 1,1′-biaryl-2,2′-diols can be obtained in high yields after only one crystallization of their salts with the chiral amidine derived from dehydroabietic acid. X-ray crystallography revealed that the amidine moiety forms a salt with the phenol group and additional intermolecular NH/π interactions contribute to the efficient chiral recognition process.

The synthesis and gelation properties of chiral β-amino acid-based low-molecular-weight organogelators, possessing methyl/trifluoromethyl side chains, are reported. The structure of the side chain and chirality were found to be important parameters affecting the gelation ability. The pure enantiomer of the trifluoromethylated β-amino acid displayed good gelation properties due to the formation of fibrillar networks, driven by enhanced amide hydrogen bonding. An investigation of the effects of the alkyl chain length showed that longer alkyl chain improved the gelation ability, yet the same supramolecular structure was observed in all, as well as an odd–even effect in both the melting points and Tg values.

In the DsTau experiment at the CERN SPS (NA65), an independent and direct way to measure tau neutrino production following high energy proton interactions was proposed. As the main source of tau neutrinos is a decay of D$_{s}$ mesons, produced in proton-nucleus interactions, the project aims at measuring a differential cross section of this reaction. The experimental method is based on a use of high resolution emulsion detectors for effective registration of events with short lived particle decays. Here we present the motivation of the study, details of the experimental technique, and the first results of the analysis of the data collected during test runs, which prove feasibility of the full scale study of the process in future. In the DsTau experiment at the CERN SPS, an independent and direct way to measure tau neutrino production following high energy proton interactions was proposed. As the main source of tau neutrinos is a decay of Ds mesons, produced in proton-nucleus interactions, the project aims at measuring a differential cross section of this reaction. The experimental method is based on a use of high resolution emulsion detectors for effective registration of events with short lived particle decays. Here we present the motivation of the study, details of the experimental technique, and the first results of the analysis of the data collected during test runs, which prove feasibility of the full scale study of the process in future.

The cobalt complexes CoIIL1(PF6)2 (1; L1 = 2,6-bis[2-(2,2′-bipyridin-6′-yl)ethyl]pyridine) and CoIIL2(PF6)2 (2; L2 = 2,6-bis[2-(4-methoxy-2,2′-bipyridin-6′-yl)ethyl]pyridine) were synthesized and used for photocatalytic CO2 reduction in acetonitrile. X-ray structures of complexes 1 and 2 reveal distorted trigonal-bipyramidal geometries with all nitrogen atoms of the ligand coordinated to the Co(II) center, in contrast to the common six-coordinate cobalt complexes with pentadentate polypyridine ligands, where a monodentate solvent completes the coordination sphere. Under electrochemical conditions, the catalytic current for CO2 reduction was observed near the Co(I/0) redox couple for both complexes 1 and 2 at E1/2 = −1.77 and −1.85 V versus Ag/AgNO3 (or −1.86 and −1.94 V vs Fc+/0), respectively. Under photochemical conditions with 2 as the catalyst, [Ru(bpy)3]2+ as a photosensitizer, tri-p-tolylamine (TTA) as a reversible quencher, and triethylamine (TEA) as a sacrificial electron donor, CO and H2 were pro...

An organocatalyst system, 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and nBu4NCl, was developed for the conversion of CO2 and internal epoxides to the corresponding disubstituted cyclic carbonates under rather mild conditions (1–4 atm of CO2 and 100–120 °C). Catalyst screening revealed that small Cl− opens epoxide rings more effectively than larger Br− and I− do when used as the counter anion of nBu4N+, suggesting that the steric hindrance of the internal epoxides is a factor. A practical and economical alternative system, DBU and nBuCl, is also presented.

We present a simple coarse-grained model with the molecular crowding effect in solvent to investigate the structure and dynamics of protein complexes including association and/or dissociation processes and investigate some physical properties such as the structure and the reaction rate from the viewpoint of the hydrophobic intermolecular interactions of protein complex. In the present coarse-grained model, a function depending upon the density of hydrophobic amino acid residues in a binding area of the complex is introduced, and the function involves the molecular crowding effect for the intermolecular interactions of hydrophobic amino acid residues between proteins. We propose a hydrophobic intermolecular potential energy between proteins by using the density-dependent function. The present coarse-grained model is applied to the complex of cytochrome f and plastocyanin by using the Langevin dynamics simulation to investigate some physical properties such as the complex structure, the electron tra...

We present a simple coarse-grained model of the effective interaction for charged amino acid residues, such as Glu and Lys, in a water solvent. The free-energy profile as a function of the distance between two charged amino acid side-chain analogues in an explicit water solvent is calculated with all-atom molecular dynamics simulation and thermodynamic integration method. The calculated free-energy profile is applied to the coarse-grained potential of the effective interaction between two amino acid residues. The Langevin dynamics simulations with our coarse-grained potential are performed for association of a small protein complex, GCN4-pLI tetramer. The tetramer conformation reproduced by our coarse-grained model is similar to the X-ray crystallographic structure. We show that the effective interaction between charged amino acid residues stabilises association and orientation of protein complex. We also investigate the association pathways of GCN4-pLI tetramer.

A hexacyclic chiral aromatic hydrocarbon (1), obtained by the reaction between indene and cyclopentadiene, has been characterized, and its enantioseparation has been achieved by the combination of stereoselective complexation with β-cyclodextrin and recrystallization. This method has been applied in the large-scale production of both pure enantiomers of 1. Enantiopure 1 and its derivatives have been used as chiral dopants in nematic liquid crystals.

The enantioseparation of three hydroxyphenylpropionic acid isomers via diastereomeric salt formation with (1 R ,2 S )-2-amino-1,2-diphenylethanol has been demonstrated. The racemates of all three acid isomers were successfully separated with high efficiency (0.56–0.84) after single crystallization. For 2-hydroxy-3-phenylpropionic acid 4 , the configuration of the less-soluble salt was controlled by the crystallization solvent: the ( R )- 4 salt was crystallized from water, while 2-propanol afforded the ( S )- 4 salt. The chiral recognition mechanism of the three acids was discussed based on the crystal structures of the diastereomeric salts.

An efficient and practical organocatalytic system comprising 3-hydroxypyridine and tetra- n -butylammonium iodide was developed for the synthesis of cyclic carbonates from carbon dioxide and epoxides under mild conditions (1 atm CO 2 , 25–60 °C) without organic solvent. By comparing with related hydroxypyridine derivatives, the effects of the hydroxyl group, the acidity and the steric factor, were discussed. Study on the mixtures of CO 2 and N 2 in various ratios indicated that the yield depends on CO 2 content, due to the solubility of CO 2 in the reaction mixture. The system was also shown not to be deteorated by the presence of H 2 O, air or O 2 .

Seven N2- and N3-ligands (L1–L7) were developed for the ligand-assisted CuI-catalyzed coupling reactions of aryl halides with phenols. The structural and electronic effects were studied for various combinations of pyridine and/or imine nitrogen binding sites in the ligands. 2-(1-Pyrazolyl)pyridine (L1) featuring two types of binding sites gave the best results, with yields of up to 90% at 100 °C at a catalyst loading of 10 mol% (CuI/L in 1:1 ratio). A non-radical mechanism, proposed for the L1-promoted coupling reaction, well explained the different effects of electronic nature of the substituent and steric hindrance on phenols and aryl halides.

The OPERA experiment discovered muon neutrino into tau neutrino oscillations in appearance mode, detecting tau leptons by means of nuclear emulsion films. The apparatus was also endowed with electronic detectors with tracking capability, such as scintillator strips and resistive plate chambers. Because of its location in the underground Gran Sasso laboratory, under 3800 m.w.e., the OPERA detector has also been used as an observatory for TeV muons produced by cosmic rays in the atmosphere. In this paper the measurement of the single muon flux modulation and its correlation with the seasonal cycle of atmospheric temperature is reported. The OPERA experiment discovered muon neutrino into tau neutrino oscillations in appearance mode, detecting tau leptons by means of nuclear emulsion films. The apparatus was also endowed with electronic detectors with tracking capability, such as scintillator strips and resistive plate chambers. Because of its location, in the underground Gran Sasso laboratory, under 3800 m.w.e., the OPERA detector has also been used as an observatory for TeV muons produced by cosmic rays in the atmosphere. In this paper the measurement of the single muon flux modulation and of its correlation with the seasonal variation of the atmospheric temperature are reported.

Chiral supramolecular hosts comprising urea-modified l-phenylalanines and achiral primary amines were developed, which facilitated enantioselective inclusion of alkyl aryl sulfoxides (3) up to 89% ee owing to the formation of ternary inclusion crystals. From the structural optimization of the components, the combination of N-(phenylcarbamoyl)-l-phenylalanine (1a) and benzhydrylamine (2e) showed the best inclusion ability among the considered supramolecular hosts. The type of the hydrogen-bonding network of ammonium-carboxylate salts 1a·2 was dependent on the steric bulk of combined primary amine 2. The rigid phenylurea moiety of 1a and moderate steric bulk of 2e played an important role in their high inclusion ability. Host 1a·2e afforded two ternary polymorphic inclusion crystals with the inclusion of acetonitrile. Furthermore, the crystal structures of 1a·2e·3 revealed that the inclusion of 3 was assisted by hydrogen bonding to the host and that stereoselectivity reversal occurred for larger sulfoxides,...

Two chiral diarylmethylamines with a phenolic hydroxy group at their ortho positions (1c and 1d) were synthesized, and their direct enantioseparation via diastereomeric salt formation was investigated. Crystallographic analyses of the diastereomeric salts involving 1c were conducted: water molecules incorporated in the space played an important role in chiral recognition. Enantiopure 1 were applied for the enantioselective addition of diethylzinc to benzaldehyde. Ligand (R)-1d afforded the product in very high yield (96%) and enantiopurity (92% ee). Not only the phenyl group on the stereogenic center of (R)-1d but also its bulky tert-butyl group is important for chiral induction.

The structure and inclusion ability of eight types of salts prepared from a combination of four tartaric acid derivatives (dibenzoyl- and three positional isomers of ditoluoyl-L-tartaric acid) and two V-shaped dianilines were investigated. They afforded 1 : 1 or 2 : 1 stoichiometric salts and the hydrogen-bonding networks changed from three-dimensional to two- and one-dimensional networks as the distance between the methyl and carboxyl groups on the tartaric acid increased. When the methylene group of dianiline was changed to an oxygen atom, the molecular structure became thinner, forming a different hydrogen-bonding network. Despite such diverse hydrogen-bonding networks, all the salts incorporated water and/or 2-butanol molecules in their structure, affording ternary or quaternary inclusion crystals.

A highly simple, economical, and selective synthesis of five-membered cyclic carbonates was achieved by the reaction of CO2 with 1,2-halohydrins in the presence of K2CO3. This method allows the efficient preparation of cyclic carbonates (72–95% yields for monosubstituted cyclic carbonates and 43% for 1,1- and 1,2-disubstituted cyclic carbonates) under mild reaction conditions, atmospheric pressure of CO2 at 30 °C, and not only in dry DMF, but also in commercial “anhydrous” DMF. The reaction mechanism was elucidated using the SEM and XRD data of the by-products, KHCO3 and KBr.

An efficient, metal- and solvent-free catalytic system was developed for the conversion of CO2 and epoxides to the corresponding cyclic carbonates under mild conditions (T = 25–45 °C, 1 atm CO2) in high-to-excellent yields. The catalyst could be easily recycled, providing a more sustainable process for the chemical fixation of CO2.