Bulletin of the Chemical Society of Japan

Nakatani, Kazuhiko

doi: 10.1246/bcsj.82.1055pmid: N/A

Mismatch binding ligand (MBL) selectively binds to mismatched base pairs with discrimination of the nucleotide bases composing the mismatch. This review focuses on the inside story regarding the molecular design of MBL and its function, and potential application in genomic science.

Morisaki, Yasuhiro; Chujo, Yoshiki

doi: 10.1246/bcsj.82.1070pmid: N/A

We synthesized π-stacked polymers by incorporating [2.2]paracyclophane units into conjugated polymer backbones and developed corresponding through-space-conjugated polymers and aromatic-ring-layered polymers. We also synthesized [2.2]paracyclophane-containing polyamidoamine (PAMAM) dendrimers and optically active polymethylenes. These polymers and dendrimers are the first well-defined and well-characterized conjugated polymers with cyclophane units in their main chain. We studied the properties of the [2.2]paracyclophane-containing through-space-conjugated polymers. We demonstrated the use of these through-space-conjugated polymers in optoelectronic applications such as an EL device. Further, we developed a synthetic strategy for new π-stacked polymers comprising layered aromatic rings on a xanthene skeleton as the scaffold. The occurrence of fluorescence resonance energy transfer from the layered cyclophanes to the end-capping aromatic moieties was verified.

Matsubara, Ryosuke; Berthiol, Florian; Nguyen, Huy V; Kobayashi, Shu

doi: 10.1246/bcsj.82.1083pmid: N/A

A novel nucleophile, sulfonylimidate, has been successfully employed in Mannich-type reactions. Due to electron-withdrawing property of sulfonyl group of sulfonylimidate, the acidity of α-proton is enhanced so that sulfonylimidate bearing no activating functional group at α-position is deprotonated by relatively weak base. DBU-catalyzed reactions of sulfonylimidates with protected imines in DMF provided the adducts in high yields with high anti selectivity. This reaction represents a wide substrate scope and a high catalytic turnover. A thorough kinetic study revealed that rate-determining step is most likely deprotonation step in case of Ts-imidate. Alkali earth metal alkoxide and its HMDS salt also catalyze Mannich-type reactions of sulfonylimidates. The reactions catalyzed by Mg(OtBu)2 in DMF provided the adducts with high anti selectivity, while those catalyzed by [Sr(HMDS)2]2 gave syn selectivity. The asymmetric variant of Mannich-type reaction of sulfonylimidate was also achieved. Several transformations of sulfonylimidates to other functional groups were also demonstrated. Finally, direct-type catalytic formation of β-amino acid ester from aldehyde and sulfonylimidate was achieved via in situ formation of sulfonylimine and DBU-assisted hydrolysis of sulfonylimidate.

Moghani, Ali

doi: 10.1246/bcsj.82.1103pmid: N/A

Matured and unmatured groups were introduced by S. Fujita who used them in the Q-conjugacy character table of a finite group (Bull. Chem. Soc. Jpn.1998, 71, 2071). He then applied his results in this area of research to enumerate isomers of molecules. In this paper, we introduce a new simple method to specify how a given finite group is matured or unmatured via some useful examples. The Q-conjugacy character tables of the fullerene C80 and tetranitrocubane are then verified.

Pratt, Lawrence M; Trần, Phương Thảo Thị; Nguỹên, Ngân Van; Ramachandran, Bala

doi: 10.1246/bcsj.82.1107pmid: N/A

Computational results are presented to support experimental evidence that cyclopropanation reactions of halomethyllithium carbenoids with alkenes occur through the concerted (methylene transfer) pathway rather than the alternate stepwise (carbometalation) pathway in non-polar and polar (THF, ε = 7.85) media. These results complement and confirm the recent findings of Ke, Zhao, and Phillips (KZP) [J. Org. Chem.2007, 72, 848] for ethylene in nonpolar and moderately polar (DME, ε = 4.34) solvents. We also studied carbenoid reactions with 2,3-dimethyl-2-butene. The explanation for the preference for the concerted pathway is provided by detailed examination of the reaction pathways of aggregated carbenoid species, which are the dominant reactive species in both polar and nonpolar solvents. The details of the syn and anti eliminations of lithium halide from the intermediate formed in the two-step mechanism with ethylene are also studied for the first time. Two stable dimeric structures were identified for the carbenoids and both have been studied. By explicit coordination of the monomeric and dimeric organolithium species to THF ligands, we also find that a clear preference for the concerted pathway is shown by both monomers and dimers in polar solvents, and solvent steric factors are dominant in determining the relative stabilities of the aggregates of the carbenoid species in THF solution.

Kitahama, Yasutaka; Tanaka, Yuhei; Itoh, Tamitake; Ishikawa, Mitsuru; Ozaki, Yukihiro

doi: 10.1246/bcsj.82.1126pmid: N/A

By lifting the limitation of ensemble measurement, concentration dependence of surface-enhanced Raman scattering (SERS) and background emission spectra were clearly observed in single Ag nanoaggregates adsorbed by thiacyanine dyes in aqueous solutions (0.5 µM–0.5 nM). Both SERS and background emission spectra at higher dye concentrations characterize the J-aggregates of thiacyanine dyes. On the other hand, no background emission was observed at lower dye concentrations, thereby suggesting that background emission is attributable to J-aggregates of thiacyanine dyes. Furthermore, temporally-stable and -fluctuating SERS spectra, together with the appearance and disappearance of SERS peaks in the 1000–400 cm−1 region, are discussed in terms of the J-aggregates and the monomers plus dimers of thiacyanine dyes.

Imamura, Yutaka; Tsukamoto, Yasuhiro; Kiryu, Hiroyoshi; Nakai, Hiromi

doi: 10.1246/bcsj.82.1133pmid: N/A

Non Born–Oppenheimer self-consistent field calculations including not only electron–electron (e–e) exchange correlation but also electron–nucleus (e–n) correlation energies have been carried out. In this study, Colle–Salvetti and B3LYP functionals for the e–n correlation and e–e exchange-correlation energies are adopted. Numerical assessments confirm that the standard enthalpies of formation are well reproduced for the G2-1 set. We also apply this method to ammoniated ammonium ion (N2H7+), one of the “vibrational bonding” systems, and discuss nuclear quantum effects such as the isotope effect.

Fujimoto, Kazuhiro; Hasegawa, Jun-ya; Nakatsuji, Hiroshi

doi: 10.1246/bcsj.82.1140pmid: N/A

Human red (HR), green (HG), and blue (HB) cone pigments are responsible for human color vision, and their photoabsorption wavelengths spread uniquely over the three primary colors. These pigments, however, include only one common chromophore, retinal. Here, we report physical basis of the color tuning in human vision on the basis of SAC-CI calculations for excited states of the cone pigments. The dominant origin of the red–green–blue distinction lies in differences in electrostatic interactions between retinal and its surrounding proteins. Structural distortion effect of the retinal chromophore is important in human blue pigment. Detailed analysis on individual roles of amino acids within these proteins has clarified elaborate mechanisms of the color tuning, in accordance with previous mutagenesis experiments. Furthermore, the color tuning is regulated by amino acids at specific positions in the proteins, suggesting some genetic origins for the color tuning.

Hatanaka, Masashi

doi: 10.1246/bcsj.82.1149pmid: N/A

Addition reactions of isocyanates were theoretically investigated. The simplest model compounds for urethanes, thiourethanes, and ureas were analyzed to find bimolecular reaction profiles. The transition states suggested intramolecular hydrogen-transfer processes, in which highly acidic hydrogens hopped.

Tomono, Kazuaki; Koyano, Ayako; Morita, Takashi; Miyamura, Kazuo

doi: 10.1246/bcsj.82.1152pmid: N/A

Five 1:1 salts of 3-X-1-methylpyridinium (X = benzoyl, acetyl, methoxycarbonyl, carboxy, and aminocarbonyl; abbreviated as Ben, Ace, Met, Car, and Ami, respectively) cations with a [Ni(dmit)2]− anion ([Ben]+[Ni(dmit)2]− (1), [Ace]+[Ni(dmit)2]− (2), [Met]+[Ni(dmit)2]− (3), [Car]+[Ni(dmit)2]− (4), and [Ami]+[Ni(dmit)2]− (5)) have been synthesized and characterized by single-crystal X-ray analysis and conductivity measurements. In the crystals, three cations 1–3 were found to form dimers by weak C–H···O hydrogen bonds, and the arrangements of cations had a strong relation with the electronic effect of the substituents. The cations of 1–3 formed similar centrosymmetrically associated dimers constructed by weak C–H···O hydrogen bonds, whose geometric parameters had a correlation with the electronic effect of the substituents. A cation of 4 also formed centrosymmetrically associated dimer, but it was made by an O–H···O hydrogen bond as usually observed in the case of carboxylic acid. In contrast with other complex salts, cations of 5 formed one-dimensional structure by C–H···O hydrogen bonding. The conductivities of salts 1, 2, 3, 4, and 5 at room temperature were 1.00 × 10−6, 1.10 × 10−6, 2.86 × 10−6, 9.77 × 10−6, and 8.75 × 10−7 S cm−1, respectively.