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81.
K. Saki Raheem Nigel P. Botting Gary WilliamsonDenis Barron 《Tetrahedron letters》2011,52(52):7175-7177
We report the first total synthesis of 3,5-O-dicaffeoylquinic acid and its derivatives, 3,5-O-diferuloylquinic acid and 3,5-(3,4-dimethoxycinnamyl)quinic acid, in a nine-step sequence. The key step involves Knoevenagel condensations between vanillin, 3,4-dimethoxybenzaldehyde or 4-hydroxy-3-methoxybenzaldehyde and the dimalonate ester of quinic acid. 相似文献
82.
83.
An efficient method for asymmetric synthesis of the potent Gastrin/CCK-B receptor antagonist AG-041R was developed. Core oxindole stereochemistry was established by asymmetric alkylation of oxindole enolates with bromoacetic acid esters, using l-menthol as a chiral auxiliary. The key alkylation reaction of the oxindole enolates generated tetrasubstituted chiral intermediates with high diastereoselectivity. The stereoselective alkylation reactions are described in detail. 相似文献
84.
Chisato Emura 《Tetrahedron》2006,62(24):5682-5685
Irciniasulfonic acid B (1) was obtained from a marine sponge, Ircinia sp., together with a known multi-drug resistance modulator irciniasulfonic acid (2). Spectroscopic and chemical analyses revealed structure consisting of common unsaturated fatty acids, a novel unsaturated branched fatty acid, and a taurine. Final separation of irciniasulfonic acid B (1) was achieved with its methylated derivatives. Irciniasulfonic acid B (1) reversed the multi-drug resistance in the same way as irciniasulfonic acid. 相似文献
85.
86.
Six new ceramide dihexosides, amphimelibiosides A-F (1-6), were isolated from a Japanese marine sponge Amphimedon sp. The structure of amphimelibioside C (3), which is a major component of amphimelibiosides, was determined by 2D NMR techniques, chemical degradation, and a semisynthetic method to be 1-O-[beta-D-glucopyranosyl-(1-->6)-alpha-D-galactopyranosyl]-(2S,3S,4R,6E)-2-[(2'R)-2-hydroxydocosanoyl]-2-amino-6-octadecene-1,3,4-triol. The structures of the other constituents were elucidated by a combination of mass spectra, (1)H NMR, and GC-MS analysis. 相似文献
87.
M. Bogdanski T. Emura S.N. Ganguli A. Gurtu S. Hamada R. Hamatsu E. Jeannet I. Kita S. Kitamura J. Kishiro H. Kohno M. Komatsu P.K. Malhotra S. Matsumoto U. Mehtani L. Montanet R. Raghavan A. Subramanian T. Yamagata 《Physics letters. [Part B]》1976,62(1):117-120
Based on a sample of about 3500 events, we have measured the total and differential cross sections of in the 700–760 MeV/c incident momentum region. It is found that σCE = 10.7 ± 0.2 mb at the average momentum of 730 MeV/c. The differential angular distribution is characterised by a sharp peak and a dip in the forward direction followed by a secondary maximum. The position of the dip corresponds to |t| ≈ mπ2. These results are compared with the predictions of the model of Bryan-Phillips. On the other hand, this dip-bump structure can be well understood on a simple picture involving a π exchange and a constant background (for |t| ? 3 mπ2). 相似文献
88.
Yoshida H Chiba Y Endo I Hayashibara I Ohsugi T Taketani A Tanaka R Amako K Arai Y Boerner H Fukawa M Fukushima Y Ishihara N Kanzaki J Kondo T Maehata M Matsui T Odaka S Ogawa K Ohama T Sakamoto H Sakuda M Shirai J Sumiyoshi T Suekane F Teramoto Y Takasaki F Tsuboyama T Uehara S Unno Y Wake M Watase Y Yamada Y Noguchi Y Ono A Homma Y Hojyo Y Sakae H Hemmi Y Kikuchi R Kubo K Kurashige H Miyake K Nakamura T Sasao N Tamura N Tobimatsu K Haba J Kamitani T Kanematsu N Nagashima Y Osabe H Sakamoto S 《Physical review letters》1987,59(26):2915-2918
89.
Daisuke Takagi Saki Okamura Kota Tanaka Naoki Ikenaga Masayuki Iwashima Seyed Mohammad Ali Haghparast Nobuyuki Tanaka Jun Miyake 《Research on Chemical Intermediates》2016,42(11):7713-7722
Apprehension over exhaustion of fossil fuels and global warming, due to increasing amounts of CO2, has generated a lot of attention for the subject of renewable energy. Renewable energy has an intermittency problem and its output fluctuates depending on natural conditions. Biohydrogen is one of the promising renewable energy sources. Hydrogen produced by photosynthetic bacteria depends on the intensity of light irradiation and also fluctuates with the daily variation of sunlight. The co-culture system of dark-fermentative and photosynthetic bacteria is one solution for reducing the dependency of hydrogen production on light intensity. Because these two strains of bacteria have different processes of hydrogen production, it is possible to combine different outputs so far as the co-culture system works well. This study performed hydrogen production by the co-culture system composed of agar gels embedded with both dark-fermentative bacteria, Clostridium butyricum MIYAIRI, and photosynthetic bacteria, Rhodobacter sphaeroides RV, under a fluctuating light-irradiation. The time-course of hydrogen production was determined for the different conditions of co-culture in the mixing ratios of the two bacterial strains and light-irradiation patterns. As a result, the co-culture system succeeded in producing hydrogen exceeding that in the case of a single culture system and improved its stability against light fluctuation. Hydrogen production by the co-culture system would be applicable to the reduction of intermittency in renewable energies. 相似文献
90.
Neslihan Saki Burcak Icli Orkun Cevheroglu Engin U. Akkaya 《Journal of inclusion phenomena and macrocyclic chemistry》2006,55(3-4):219-222
In an attempted synthesis of peripherally pyridine-substituted cucurbituril, an unexpected cyclized product was obtained. A careful NMR analysis followed by mass spectrometry and preliminary crystallographic analyses, helped us in resolving the structure. The structure has two quaternized pyridine functionalities and a groove suitable as a potential receptor site. In addition, just like the parent glycoluril structure, two remaining urea-derived nitrogens can be alkylated by alkyl halides. Thus, we believe this high yielding reaction may become an entry point to a new class of anion receptors. 相似文献