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131.
Hinata Yokokawa Seiya Ishizawa Dr. Katsuya Saito Dr. Yasuhiro Meguro Prof. Shigefumi Kuwahara Dr. Masaru Enomoto 《European journal of organic chemistry》2023,26(6):e202201482
The first total synthesis of aculene D, a structurally rare nordaucane-type natural product exhibiting quorum sensing inhibitory activity, has been accomplished from a known five-membered hydroxy carboxylic acid. Nucleophilic addition of methallylzinc bromide to a β-keto aldehyde intermediate under Barbier conditions to install the secondary hydroxy group on the seven-membered ring of aculene D gave the corresponding alcohol with an undesired configuration predominantly. On the other hand, the protection of its keto group as the ethylene acetal induced a reversal of diastereoselectivity, affording a desired diastereomer in a selective manner. The construction of the seven-membered ring was realized by ring-closing metathesis using a triethylsilyl-protected monocyclic diene ester precursor. An additional five-step manipulation on the cyclization product including the installation of an ethyl group on the five-membered ring completed the synthesis of aculene D, whose esterification with an N-protected l -proline followed by deprotection also achieved the first total synthesis of aculene B. 相似文献
132.
For the solid-state photoisomerization of benzyl (Z,Z)-muconate to the corresponding (E,E)-muconate, the direct observation of a change in the crystal structure has revealed that the isomerization occurs by a topochemical reaction process according to a bicycle-pedal model and is finally accompanied by a phase transition to a stable crystal structure. 相似文献
133.
A photochromic diarylethene containing naphthyl groups formed a chiral crystal when co-crystallized with octafluoronaphthalene, although both molecules are achiral, and underwent highly enantioselective photocyclization owing to the conformational confinement in the crystal. 相似文献
134.
Seiya Negami 《Discrete Mathematics》2012,312(5):973-991
A graph is said to be -distinguishable if there is a labeling such that no automorphism of other than the identity map preserves the labels of vertices given by . The smallest for which is -distinguishable is called the distinguishing number of . We shall prove that every 4-representative triangulation on a closed surface, except the sphere, is 2-distinguishable after establishing a general theorem on the distinguishability of polyhedral graphs faithfully embedded on closed surfaces, and show that there is an upper bound for the distinguishing number of triangulations on a given closed surface, applying the re-embedding theory of triangulations. 相似文献
135.
Uchida K Walko M de Jong JJ Sukata S Kobatake S Meetsma A van Esch J Feringa BL 《Organic & biomolecular chemistry》2006,4(6):1002-1006
Upon UV irradiation of the hydrogen-bond confined crystal state of a dithienylhexafluorocyclopentene with (R)-N-phenylethylamide substituents, the photochemical cyclization reaction proceeds diastereoselectively to form the coloured, closed-ring isomer with 97% de. 相似文献
136.
A diarylethene derivative bearing a phenylenediamine group formed radical ions with an electron acceptor molecule in solution, and the concentration of the radical ions was modulated by the photochromic reaction of the diarylethene, reflecting the difference in the electron-donating character between the open- and closed-ring isomers. 相似文献
137.
138.
Jun Manabe Nagisa Sako Mizuki Ito Dr. Masaru Fujibayashi Dr. Chisato Kato Dr. Goulven Cosquer Prof. Katsuya Inoue Dr. Kiyonori Takahashi Prof. Takayoshi Nakamura Prof. Tomoyuki Akutagawa Dr. Seiya Shimono Dr. Hiroki Ishibashi Prof. Yoshiki Kubota Prof. Sadafumi Nishihara 《欧洲无机化学杂志》2023,26(34):e202300449
Materials exhibiting irreversible phase transitions, leading to changes in their properties, have a potential for novel application in electronic components such as a non-rewritable high-security memory. Here, we focused on the two salts, [(9-triptycylammonium)([18]crown-6)][Ni(dmit)2] ( 1 ) and [(9-triptycylammonium)([15]crown-5)][Ni(dmit)2] ( 2 ), which featured 2D sheet structures with alternately stacked cation and anion layers. Both salts exhibit similar cation arrangements, however, their anion arrangements differ significantly. The temperature-dependent magnetic susceptibilities of 1 and 2 were well reproduced by the alternating chain model (JAC1/kB=−306(8), JAC2/kB=−239(3) K) and the Curie-Weiss model (θ=−3.9(1) K), respectively. 1 experience a reversible phase transition around 40–60 K, causing anomalies in magnetic behavior. Moreover, an irreversible single-crystal-to-single-crystal phase transition to 1′ undergo at ~381 K, inducing a rearrangement of [Ni(dmit)2]− anions and a resistivity decrease from 6.5×106 to 6.5×102 Ω cm. The susceptibility curve of 1′ was reproduced by a combination of the Curie-Weiss and dimer models (Jdimer/kB=−407(5), θ=−26.7(5) K). The irreversible transition of 1 is the first example for such supramolecule and [Ni(dmit)2]− system to our knowledge, in opening potential new-type materials. 相似文献