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排序方式: 共有397条查询结果,搜索用时 15 毫秒
1.
Rikuhei Tanikaga Yoshimasa MatsumotoMaki Sakaguchi Yohei KoyamaKentaro Ono 《Tetrahedron letters》2003,44(35):6781-6783
Lipase-mediated acetylations of trans- and cis-2-substituted cyclohexanols gave the corresponding (1R)-cyclohexyl acetates and (1S)-cyclohexanols in high yields and ee, but c-4-tert-butyl-c-2-ethenyl-r-1-cyclohexanol was unreactive owing to the steric interaction between the axial OH group and the axial H atoms at the 3- and 5-positions. In the cis-isomer the OH group occupies an equatorial position to bind to the lipase, and less bulky axial alkenyl and alkynyl groups might not so much prevent acetylations than an alkyl group. 相似文献
2.
The title compound a novel cyclophane containing p-tropoquinone, was synthesized starting from 5-methoxytropolone and its physical properties were discussed comparing with those of 3,7-dimethyl-p-tropoquinone and p-benzoquinonophane. The reduced quinone character exhibited by was ascribed to the intramolecular CT interaction and the deformation of the quinone ring. 相似文献
3.
The complete structure of palytoxin (1) was elucidated by us in 1982.1 Our continuous interests in palytoxin led us to examine minor constituents of Okinawan Palythoa tuberculosa. In this paper, we describe successful isolation and structural elucidation of four minor toxins, which were named homopalytoxin (2), bishomopalytoxin (3), neopalytoxin (4) and deoxypalytoxin (5). 相似文献
4.
5.
Yoshimasa Fukazawa Satoshi Harada Akira Inai Toshiya Okajima 《Tetrahedron letters》1993,34(52):8493-8496
The title compound (2) has been synthesized, the structure and the physical properties of which are investigated by X-ray, spectroscopic analyses, and MO calculations. There exists charge transfer (CT) interaction between the tropylium ion and the facing phenyl ring. From the pKR+ value of 2, it can be clear that the cation 2 is stabilized by the CT interaction. In spite of the presence of bond weakening σ-π orbital mixing, the cation 2 withstands retro[4+4]type bond cleavage, which is quite interesting when compared to a facile cleavage for the congener with anthracene photodimer type structure. 相似文献
6.
Kunihisa Yoshida Yoshimasa Toyo-Oka Kazusada Takeda 《Journal of heterocyclic chemistry》1995,32(2):701-702
The electrooxidation of 1-methylpyrazole in methanol containing sodium cyanide produced 1-methyl-pyrazole-4-carbonitrile 2 and ?5-carbonitrile 3 in yields of 23 and 8%, respectively (2e-oxidation products), together with 4-methoxy-1-methylpyrazole-5-carbonitrile 4 (4e-oxidation product, 4%). 相似文献
7.
Tetsuo Suami Hiroaki Sasai Kazuhiro Matsuno Nobuo Suzuki Yoshimasa Fukuda Osamu Sakanaka 《Tetrahedron letters》1984,25(40):4533-4536
Tunicamycins and their eight analogs have been synthesized by condensation of a N-acetyl-D-glucosamine derivative and an anomeric chloride of tunicaminyl uracil, followed by deprotections and N-acylation. 相似文献
8.
The resonance Raman spectra of tris(acetylacetonatoiron(III)) and ruthenium(III) complexes in various solvents and in water-acetonitrile (W-AN) mixtures were measured. The resonance Raman spectra of both complexes indicated peaks near 460 and around 1580 cm–1. Thev(C-O) peak (around 1580 cm–1) is shifted to low frequency with an increase in the dielectric constant T of the solvents, whereas thev(M-O) (M=Fe and Ru, near 460 cm–1) are constant, independent of T. It implies that the C-O bond in the acac– ligand is lengthened by the polarizability effect of the solvents, while both the Fe-O and Ru-O bonds, which are located in the inside of the complexes, are not influenced by the solvents indicating that the interaction does not depend on the properties of individual solvent molecules but on those of the aggregate. 相似文献
9.
Resorcinol and 5-methylresorcinol, respectively, react with 3-oxo-2-aryl-4,4,4-trifluorobutyronitrile using zinc chloride as a catalyst in dibutyl ether under the Hoesch reaction conditions to give a low yield of 3-aryl-7-hydoxy-4-trifluoromethyl- or 3-aryl-5-hydroxy-7-methyl-4-trifluoromethyl-2H-l-benzopyran-2-ones. However, the related reaction with m-methoxyphenol was found to produce poor yields of 3-aryl-7-methoxy-4-trifluoromethyl-2H-1-benzopyran-2-one and its 3,4-dihydro-4-hydroxy derivative. 相似文献
10.
Shunichi Manabe Kazumasa Wakamatsu Yoshimasa Hirata Kiyoyuki Yamada 《Tetrahedron》1979,35(16):1925-1929
13C NMR spectra are reported for derivatives of toxic sesquiterpenes, anisatin (I) and neoanisatin (II). Chemical shifts for each compound have been assigned on the basis of off-resonance decoupling experiments, known chemical shift rules, and comparison of the spectra among the compounds examined. Toxic anisatin (I) is known to isomerize under mild conditions to a non-toxic compound, anisatinic acid. The structure of anisatinic acid has been determined unambiguously to be IIIa by the 13C NMR spectral analysis of a derivative 8 of anisatinic acid. Some aspects of the substituent effects on the 13C chemical shifts obtained in the present investigation are described. 相似文献