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A series of boronic acid-containing saccharide receptors was synthesised via copper catalysed azide–alkyne cycloaddition (CuAAC) reactions. Their saccharide binding capacity was studied by 1H and 11B NMR spectroscopy titrations and isothermal titration calorimetry (ITC) techniques. Fluorescent sensors were generated by linking a phenylboronic acid (PBA) receptor with fluorophores via a triazole-linker. Fluorescence titrations with fructose revealed that the substitution pattern about the PBA influences the fluorescence response to saccharides. Titrations studied by 1H NMR spectroscopy suggested that fructose binding is enhanced when the aromatic ring bearing the boronic acid has the triazole-containing substituent at the ortho position. No evidence of either a dative N–B bond or solvent insertion (between B and N) was observed by 11B NMR spectroscopy. These results demonstrate that synthetic accessible triazole receptors may allow rapid sensor synthesis, screening and discovery.

ConspectusNitrogen fixation is an essential chemical process both biologically and industrially. Since the discovery of the first transition-metal–dinitrogen complex in 1965, a great deal of effort has been devoted to the development of artificial nitrogen fixation systems that work under mild reaction conditions. However, the transformation of chemically inert dinitrogen using homogeneous catalysts is still challenging because of the difficulty in breaking the strong triple bond of dinitrogen, and a very limited number of transition metal complexes have exhibited the catalytic activity for the direct transformation of dinitrogen into ammonia with low turnover numbers. To develop more effective nitrogen fixation systems, it is necessary to retrieve as much information as possible from the limited successful examples. Computational chemistry will provide valuable insights in the understanding of the reaction mechanisms involving unstable intermediates that are hard to isolate or characterize. We have been ...

The synthesis and reactions of 3,4-benzo-1,2-disilacyclobut-3-enes and benzo[1,2:4,5]bis(1,2-disilacyclobut-3-ene)s developed by our group are reported in this review. The palladium-, platinum- and nickel-catalyzed reactions of benzodisilacyclobutenes and benzobis(disilacyclobutene)s with unsaturated compounds afford various types of products. The structures of the products are dependent upon the nature of the transition metal used as a catalyst. The reactions of cis- and trans-benzodisilacyclobutenes with alkenes and alkynes in the presence of a transition-metal catalyst proceed with high stereospecificity to give the respective adducts. The thermal reactions of cis- and trans-benzodisilacyclobutenes with various substrates also proceed stereospecifically to give adducts. The results of theoretical calculations for the platinum-catalyzed reaction of disilacyclobutene with acetylene, the nickel-catalyzed reaction of benzodisilacyclobutene and the thermal reaction of benzobis(disilacyclobutene) are discussed in this review.

The development of green processes for the direct synthesis of H 2 O 2 from H 2 and O 2 is of environmental and commercial importance. Basic understanding toward the high activity and selectivity of the PdAu bimetallic catalysts will be helpful for its further improvement. In this mini review main results in our previous studies are discussed and summarized. A mechanistic explanation for the origin of the high activity and selectivity achieved on the PdAu catalysts is put forward on the basis of that the effect of the co-adsorbed H atoms on the PdAu surface is taken into account. The role of the catalyst in the direct H 2 O 2 synthesis might be just to supply active H atoms, by cleaving H 2 molecule, as the feedstock for the hydrogenation of O 2 . It is shown from our DFT calculations that on the PdAu bimetallic catalyst the high activity of Pd and the high selectivity of Au are balanced and then high overall performance is accomplished for the synthesis of H 2 O 2 .

Palladium-catalyzed decarboxylative coupling of benzoic acid derivatives with arylboroxins gave biaryls using a catalytic amount of Pd(TFA) 2 –hydrazone 1d system with Ag 2 CO 3 at 80 °C in good yields. We also found that decarboxylative coupling with aryl(trialkoxy)silanes gave biaryls using a Pd(TFA) 2 –hydrazone 1g system with AgF in good yields.

Quantum chemical studies by the author and co-workers on dioxygen activation and methane hydroxylation by diiron and dicopper enzyme species as well as related metal–oxo species are reviewed. The a...

Anthracene, with its molecular panel-like shape and robust photophysical behaviour, is a versatile building block that is widely used to construct attractive and functional molecules and molecular assemblies through covalent and non-covalent linkages. The intrinsic photophysical, photochemical and chemical properties of the embedded anthracenes often interact to engender desirable chemical behaviours and properties in multi-anthracene assemblies. This review article focuses on molecular architectures with linear, cyclic, cage, and capsule shapes, each containing three or more anthracene subunits.

The four stereoisomers of YCZ-2013 are synthesized and their effects on Arabidopses stem elongation is studied.

A conformational search method based on the density functional theory (DFT) was successfully applied to explore a mechanism for the highly enantioselective alkylation by binaphthyl-modifed chiral phase-transfer catalysts. Key interactions that govern the enantioselectivity were analyzed. The computational results are encouraging for further application of the DFT-based conformational search toward the rational design of next-generation asymmetric phase transfer catalysts.

Hydrolytic enantioselective protonation of dienyl esters and a β-diketone catalyzed by phase-transfer catalysts are described. The latter reaction is the first example of an enantio-convergent retro-Claisen condensation. Corresponding various optically active α,β-unsaturated ketones having tertiary chiral centers adjacent to carbonyl groups were obtained in good to excellent yields and enantiomeric ratios (83-99%, up to 97.5:2.5 er).

The macrocycle (III) is obtained in low yield by Suzuki coupling of diboronic acid (I) with ditriflate (II).

The ring expansion reaction of ethyl cyclopropylideneacetate (1) with benzosilacyclobutenes proceeded smoothly in the presence of Ni(cod)2-TOPP (tribiphenyl-2-yl phosphite) to give benzosilacycloheptenes in good yields. This formal σ bond metathesis reaction proceeded in a selective manner. The Ni-catalyzed reaction of 1 with biphenylenes was also examined.

Carbonyl compounds react with benzyl chloromethyl ether in the presence of samarium(II) iodide to afford the corresponding addition products which, when subsequently hydrogenolysed, yield 1,2diols. Simple aldehydes and ketones react with diiodomethane in the presence of samarium metal to give iodohydrins in good yields. Under similar reaction conditions, α-halogeno substituted ketones and aromatic 1,4-diketones are converted into cyclopropanols. These cyclopropanations have been shown to proceed through the initial generation of samarium enolates, followed by the Simmons Smith type reaction. A novel transformation of esters to cyclopropanols via tandem one-carbon homologation is also described.

The ESR spectrum of the cationic triradical of 1,3,5-tris(diphenylamino)benzene (TDAB) is discussed. The tricationic state of TDAB was observed by means of cyclic voltammetry. The orange cationic triradical was prepared by oxidation of TDAB with trifluoroacetic anhydride in the presence of tetra-n-butylammonium tetrafluoroborate in CH 2 Cl 2 . The ESR spectrum of the randomly oriented radicals in the CH 2 Cl 2 glass agrees well with the theoretical prediction of a quartet (S=3/2) spin state with a zero-field splitting parameter D' of 13.1 G (0.0012 cm -1 )

Treatment of RMgX (1 equiv. R = alkyl; X = Cl, Br) with ZnCl 2 (1 equiv.) in a mixed solvent of THF and Et 2 O leads to a highly turbid white suspension. Addition of LiCl (1∼2 equiv.) solubilizes the insoluble species to yield a colorless clear solution. Addition of a catalytic amount of a Cu(II)-salt followed by allylic halides or mesylates at 0 °C ∼ room temperature yielded S N 2′products in high yields. Application for the synthesis of ( E )-alkene dipeptide isosteres is also reported.

The benzyl phosphate-protection for phosphoamino acid is very useful for Boc mode solid-phase synthesis of phosphopeptides. A phosphothreonine-containing peptide related to the EGF receptor protein was synthesized by use of this methodology.

新しい低原子価サマリウム試剤の調製と反応について検討を行った。金属サマリウムと臭素Br2を4:3のモル比で反応させることにより,Sm-SmBr3系反応試剤を調製した,本反応試剤の還元力はヨウ化サマリウム(II)のそれよりも強いことが観察された。たとえば,ヨウ化サマリウム(II)では還元されない芳香族エステルが本反応試剤と室温で容易に反応し,還元的に二量化した生成物を与えた。また,この試剤とシクロプロパン-1,2-ジカルボレ酸ジエチルとの反応では三員環の還元的開裂が起こり,グルタル酸ジエチルが生成した。また,SmBr3-n-BuLi系反応試剤を用いた場合にも,芳香族エステルが還元的に二量化した生成物を与えた。一方,金属サマリウムとヨウ化水銀または臭化水銀を組み合わせた試剤と,シクロプロパン-1,11ジカルボン酸ジメチルの反応は室温で円滑に進行し,ビス[3,3-ビス(メトキシカルボニル)プロピル]水銀が良好な収率で生成した。

2-Quinolinylmethyl thioethers were efficiently cleaved to generate the corresponding symmetrical disulfides using the following systems; FeCl3/N,N-dimethylformamide (DMF)/H2O, FeCl3/ethanol (EtOH)/H2O, and CuCl2/DMF/H2O. The 2-quinolinylmethyl group was utilized as a thiol protecting group in the synthesis of a model peptide.

The time‐resolved spectroscopy in polydiacetylene single crystals (PDA‐MADF {poly‐1‐[3‐(methylamino)phenyl]‐4‐[3,5‐bis(trifluoromethyl)phenyl]‐1, 3‐butadiyne}) on femtosecond and picosecond time scales was performed. The time dependence of the photoinduced reflectance change in PDA‐MADF exhibits three components with lifetimes ∼200 fs, 1–2 ps, and ≫200 ps. These components are assigned to the free 1Bu excitons, self‐trapped excitons, and triplet excitons. From the excitation intensity dependence of the reflectance change, a significant role of bimolecular interactions between singlet excitons for the formation of triplet excitons is clarified. A model of the mechanism of triplet exciton formation after the creation of singlet excitons is proposed.

This account recounts the application of self-assembled coordination hosts as molecular tools and the development of unusual chemical reactions and interactions generated within their cavities. Starting from the simple molecular recognition of guest molecules, coordination hosts have been used to accelerate reaction rates, endow regio- and stereoselectivity, and create unique reactions in their nanometer-sized cavities. Coordination hosts were also used to develop a new, practical method for constructing discrete stacks of aromatic molecules with unique electronic and magnetic properties.

Dimethyl cyclopropane-1,1-dicarboxylate is readily subjected to reductive ring opening reaction with samarium(II) iodide in the presence of tris(dibenzoyl-methiodo)iron(III). The generated organosamarium intermediate is trapped by aliphatic ketones to afford 5,5-disubstituted 2-methoxycarbonyl-5-pentanolides.

Two new xanthones, garciniaxanthone D (1) containing a dihydrobenzofuran ring and 1,4,5-trihydroxyxanthone (2), have been isolated from Garcinia subelliptica as superoxide anion scavengers. Their structures have been determined mainly by spectroscopic methods and some chemical reactions.

A new mycotoxin, sambutoxin (1), has been isolated from wheat culture of Fusarium sambucinum which was obtained from rotted potato tuber. Its chemical structure was elucidated as 3-{5-methyl-6-[( E )-1,3,5-trimethylhept-1-enyl]tetrahydropyranyl}-5-( p -hydroxyphenyl)-1-met -4-hydroxy-2(1 H )-pyridone mainly by NMR analyses of 1 .

(SP)-9-Anthryl(l-menthyloxy)phenylphosphine-borane and (SP)-(1-l-menthyloxy)benzo[b]phosphole-borane were synthesized, and their structures were characterized by X-ray crystallographic analysis. The latter compound was reduced by lithium naphthalenide at −78°C with cleavage of the PO bond, and the subsequent reaction with electrophiles afforded the corresponding tertiary phosphine-boranes possessing good to excellent enantiomeric excesses.

The geometrical and electronic structures of large cyclic polyenes, annulenes, with 18, 30, 42, 54, and 66 CH units, which belong to a subgroup of aromatic (4n + 2)π electron systems and can exhibi...

Three new prenylated xanthones, garciniaxanthones F (1), G (2) and H (3), have been isolated as antioxidative substances from the wood of Garcinia subelliptica (Guttiferae). Their structures have been elucidated on the basis of spectroscopic data involving comparison of their 13 C-NMR data with those of previously known xanthones. The antioxidant properties of the new compounds have been evaluated by three assay systems : anti-lipid peroxidation, α,α-diphenyl-β-picrylhydrazyl radical scavenging activity and superoxide radical scavenging activity.

A new route to the disaccharide moiety (2-O-(3-O-carbamoyl-α-d-mannopyranosyl)-l-gulopyranose) of the antitumor agent bleomycin was developed. Both the l-gulose synthon 21 and the 3-O-carbamoyl-d-mannose segment 30 were prepared from d-mannose in a regioselective manner by applying stannylene acetal methodology. Glycosylation of 21 with 30 proceeded smoothly, and further conversion to disaccharide derivatives (33 and 34) was successfully accomplished.

A library of 16 hexasaccharides related to landomycin A is prepared, by the synthesis of eight distinct trisaccharides and selective β-glycosylation between the glycosyl donors and acceptors.

The ionization-potential and oxidation-potential values have been examined as stability parameters in the gas and solution phase, respectively, for cyclopentadienide ions with from one to four condensed aromatic rings. They indicate that, without solvation effects, the condensed aromatic rings intrinsically stabilize the cyclopentadienide ion in solution as well as in the gas phase, and that an apparent destabilization effect by the aromatic rings in solution is most probably ascribed to a decrease in the stabilizing solvation effects due to charge delocalization on the carbanions. Theoretical investigations from governing orbital interactions using the frontier orbital theory demonstrate that the essential stability of the cyclopentadienide ions is dependent on the structure, itself.

The minimum energy migration path and the minimum barrier height of lithium diffusion are discussed for the layer compound LixCoO2. The Universal Force Field (UFF) is adapted for use in solid state compounds. Molecular dynamics simulations with additional impulse dynamics method, performed at a microcanonical ensemble, point out that the lithium migration between the Co–O octahedron layers takes place by ion hopping from one octahedral to another octahedral site via an interstitial tetrahedral site. The barrier height of lithium migration is estimated to be 28.7 kJ mol−1 (0.30 eV) for an original layer distance of 2.54 A; a potential energy profile is developed from molecular mechanics calculations. The observation that the repulsive van der Waals interaction between Li+ and neighboring O2− ions is the most important contribution to the barrier height is consistent with the fact that the activation energy of lithium diffusion is very sensitive to the layer distance, within the experimentally observed values.

A series of ethyl 7-amino-2,4-dioxopteridine-6-carboxylates 4 and ethyl 7-amino-4-oxo-2-thioxopteridine-6-carboxylates 5, of interest biologically, has been prepared in one step from the reaction of such vicinal-diamines as 1,3-dialkyl-5,6-diaminouracils 2 or 1,3-dialkyl-5,6-diamino-2-thiouracils 3 with diethyl (E)-2,3-dicyanobutenedioate (1). Moreover, ethyl 3-amino[1,2,4]triazino[2,3-a]-1H-benzimidazole-2-carboxylate (11) was also obtained from the reaction between 1,2-diamino-1H-benzimidazole (10) and 1. The structural studies of 4, 5, and 11 prepared were carried out by nmr experiments in some details.

A disulfide-bridged dicopper(I) complex [Cu2(Py2SSPy2)](ClO4)2 (1), synthesized by the redox reaction of a Cu(II) salt with a thiol-containing N3S-donor ligand, N,N-bis[2-(2-pyridyl)ethyl]-2-mercapto-2-methylpropylamine (Py2SH), is demonstrated to catalyze epoxidation and hydroxylation with H2O2 as an oxidant.

Claisen and Cannizzaro reactions were found to proceed efficiently under solvent-free conditions. The solvent-free Claisen reactions were especially effective for the ester substituted with sterically bulky groups, which does not react in solution.