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961.
D. Ishii T. Yamada M. Nakagawa T. Iyoda H. Yoshida 《Journal of Thermal Analysis and Calorimetry》2006,86(3):681-685
The
thermally induced structural transformation of a hydrogen-bonded crystal formed
from an amphoteric molecule of 6-[2-methoxy-4-(pyridylazo)phenoxy]hexanoic
acid MeO was studied using differential scanning calorimetry (DSC), Fourier
transform infrared spectroscopy (FTIR) and X-ray diffraction measurement (XRD).
Crystal form of the hydrogen-bonded crystal was measured by single crystal
four circle diffractometer (Mo-Kα radiation). As
a result, the crystal of MeO was stabilized by many C–H⋅⋅⋅O hydrogen
bonds, and the C–H⋅⋅⋅O hydrogen bonds were broken by thermal energy
reversibly. After transformation the supramolecular architecture was composed
of supramolecular polymer including free-rotation pentamethylene main chains. 相似文献
962.
963.
Kazuhiko Sakaguchi Masahiro Yamamoto Takeshi Yamada Keiko Shimamoto 《Tetrahedron letters》2004,45(30):5869-5872
The synthesis of four types of optically active β-carbon-substituted analogs of threo-β-hydroxy aspartate (THA) and a β-carbon-substituted analog of threo-β-benzyloxy aspartate (TBOA), which are potent blockers of excitatory amino acid transporters in the mammalian central nervous system, via the chirality-transferring ester-enolate Claisen rearrangement of α-acyloxytrialkylsilane is described. 相似文献
964.
965.
966.
967.
968.
Bunichiro Yamada Toshihiko Tanaka Shigeki Mori Takayuki Otsu 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(6):697-710
Ceiling temperatures (Tc) and reactivities of N-phenylmethacrylamide (PMAm) and o-substituted PMAm's in free-radical polymerization and the thermal stability of the polymers obtained were investigated. Although PMAm and o-substituted analogs gave the same Tc, 123°C at 0.64 mol/L in N,N-dimethylformamide, that of 2,6-dimethyl-PMAm was found to be as low as 65°C. These findings are interpreted in terms of steric hindrance as a consequence of the bulkiness of the 2- and 6-substituents and of the rigid and planar structure expected for the polymers. In copolymerization with styrene, the o-monosubstituted PMAm's were estimated to be more reactive than PMAm by a factor of about 3 except for o-phenyl-PMAm. The enhanced reactivity of the PMAm with a relatively small o-substituent is explained by ground-state strain of the monomer tending toward a planar structure. 2,6-Dimethyl-PMAm and o-phenyl-PMAm showed lower and slightly higher reactivities than PMAm, respectively, probably due to the blocking effect of these substituents against the approaching polymer radical. Enhancement of thermal degradation owing to the substitution was confirmed by means of thermogravimetric analyses of the polymers. The polymers from the 2,6-dimethyl-substituted and the o-monosubstituted PMAm' exhibited similar maximum-degradation-rate temperatures. 相似文献
969.
Kenji Yamada Tatsuo Mitsutake Motowo Takayanagi Tisato Kajiyama 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(6):891-902
Poly(p-phenylene-3,4′-oxydiphenylene terephthalamide) (PPOT) and poly(4,4′-oxydiphenylene-4-carbonamidephthalimide-N-yl) (PAI) are compatible. Molecular composites were prepared by solution blending and subsequently solvent casting. The glass transition temperature of the composite increased with increasing fraction of PPOT. Intermolecular interactions between the two components increase due to formation of hydrogen bonds between the amide linkages of the component polymers. The elastic modulus of the composite was always higher than the modulus predicted on the basis of the additivity. Similar deviations from additivity were observed for the bulk density. These desirable results arise from an increase of the packing density of molecules due to the additional hydrogen bonding also shown by the infrared spectra. 相似文献
970.
Kohei Yamashita Yuji Kume Seiya Ashibe Cicilia A. D. Puspita Kotaro Tanigawa Naoki Michihata Prof. Dr. Shinnosuke Wakamori Prof. Dr. Kazutada Ikeuchi Prof. Dr. Hidetoshi Yamada 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(69):16408-16421
The total synthesis of mallotusinin, which bears a tetrahydroxydibenzofuranoyl (THDBF) bridge between the 2-oxygen and 4-oxygen of glucose on corilagin with a 3,6-O-(R)-hexahydroxydiphenoyl (HHDP) bridge, is described. The key features of the total synthesis are: 1) improvements of our previously reported method to synthesize corilagin; 2) establishment of the THDBF skeleton via an unusual intramolecular SNAr reaction of an HHDP analogue, and 3) the application of a two-step bislactonization strategy for a HHDP bridge construction into the 2,4-O-THDBF bridge. Oxidative phenol coupling of 1,2,4-orthoacetyl-3,6-di-(4-O-benzylgalloyl)-α-d -glucopyranose and the orthoester cleavage of the coupling product without the pyranose-furanose ring transformation are key reactions for the improved synthesis of corilagin, which enabled the adequate supply of a corilagin precursor that was required to develop the mallotusinin synthesis. These established methods are expected to help develop the synthesis of other ellagitannins with a bridge between the two oxygens of corilagin. 相似文献