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排序方式: 共有120条查询结果,搜索用时 296 毫秒
31.
Toshiyasu Inuzuka Yutaka Yamamoto Kaoru Yamada Daisuke Uemura 《Tetrahedron letters》2012,53(2):239-242
A polyol compound, amdigenol A, was isolated from the dinoflagellate Amphidinium sp. that adhered to the surface of the marine alga Digenea simplex. A structural elucidation was performed by 2D-NMR spectroscopy, degradation with a second generation Hoveyda–Grubbs catalyst and ESI-CID-MS/MS analyses. Amdigenol A consists of a C98-linear carbon backbone including two core structures of amphidinol analogs and is likely formed linearly by two amphidinol analogs. 相似文献
32.
This paper shows applications of the back-action evading amplifier, which amplifies a signal without degradation of the signal-to-noise ratio (SNR), to optical decoupling systems and clarifies the effects of the number of branches and the amplitude gain to SNR. As a result, it is shown that this concept provides an ideal optical system for networks with optical branches. 相似文献
33.
Akira Okada Satoshi Yokojima Noriyuki Kurita Yasuo Sengoku Shigenori Tanaka 《Journal of Molecular Structure》2003,630(1-3):283-290
A theory for charge transfer between the electrode and the donor/acceptor molecule coupled through a DNA bridge in solution is developed. We explore the crossover between the coherent tunneling and the incoherent sequential transfer regimes by varying the electrode potential and discuss the effects of single-base mismatches in DNA duplex in both regimes. In the former regime a single-base mismatch in DNA duplex causes a reduction in the charge transfer rate simply by decreasing the electron tunneling matrix element, however, in the latter regime the effects are rather complicated. 相似文献
34.
Tetsuya Sengoku 《Tetrahedron》2008,64(35):8052-8058
An enantiomerically and diastereomerically pure route has been developed for the first asymmetric synthesis of (1S,2R,3R,5R,7aR)- and (1S,2R,3R,5S,7aR)-1,2-dihydroxy-3,5-dihydroxymethylpyrrolizidine, hyacinthacine B1 and B2, featuring efficient and stereodefined elaboration via the asymmetric dihydroxylation (AD) of the functionalized homochiral pyrrolidine derivative prepared from (S)-(−)-2-pyrrolidone-5-carboxylic acid. 相似文献
35.
Iwanami K Choi JC Lu B Sakakura T Yasuda H 《Chemical communications (Cambridge, England)》2008,(8):1002-1004
The presence of the heterogeneous mesoporous Al-MCM-41 catalyst remarkably accelerated the cyanosilylation of various aldehydes and ketones with trialkylsilyl cyanide, giving the corresponding cyanohydrin silyl ethers in quantitative yields under mild reaction conditions. 相似文献
36.
Fanconi anemia (FA) is a rare genetic disorder characterized by aplastic anemia, cancer/leukemia susceptibility and cellular hypersensitivity to DNA crosslinking agents, such as cisplatin. To date, 12 FA gene products have been identified, which cooperate in a common DNA damage-activated signaling pathway regulating DNA repair (the FA pathway). Eight FA proteins form a nuclear complex harboring E3 ubiquitin ligase activity (the FA core complex) that, in response to DNA damage, mediates the monoubiquitylation of the FA protein FANCD2. Monoubiquitylated FANCD2 colocalizes in nuclear foci with proteins involved in DNA repair, including BRCA1, FANCD1/BRCA2, FANCN/PALB2 and RAD51. All these factors are required for cellular resistance to DNA crosslinking agents. The inactivation of the FA pathway has also been observed in a wide variety of human cancers and is implicated in the sensitivity of cancer cells to DNA crosslinking agents. Drugs that inhibit the FA pathway may be useful chemosensitizers in the treatment of cancer. Publication history: Republished from Current BioData's Targeted Proteins database (TPdb; http://www.targetedproteinsdb.com). 相似文献
37.
Jolanta WierzejskaManami Ohshima Toshiyasu InuzukaTetsuya Sengoku Masaki TakahashiHidemi Yoda 《Tetrahedron letters》2011,52(11):1173-1175
The first total synthesis of (+)-batzellaside B and its C8-epimer was completed from a known l-arabinose-derived tribenzyl ether in 22 steps with overall yields of 3.9% and 5.4%, respectively. The absolute configuration of (+)-batzellaside B was unambiguously determined to be 1S,3S,4S,5R,8S by the Mosher analysis of a synthetic intermediate prepared through a separate route. 相似文献
38.
Takuma Takemura Ichiro Hayakawa Emi Fukasawa Tetsuya Sengoku Hideo Kigoshi 《Tetrahedron》2012,68(32):6477-6484
The diastereoselective aldol-type reaction of a γ-pyrone via a sodium anion has been developed. This reaction is useful for synthesizing γ-pyrone-containing natural products. Also, we applied the Mukaiyama aldol-type reaction of silyl enol ether of γ-pyrone by using TiCl4. This Mukaiyama aldol-type reaction of γ-pyrone indicated higher anti-aldol selectivity than the aldol-type reaction of a γ-pyrone with NaHMDS. 相似文献
39.
[10]Cycloparaphenylene ([10]CPP) was selectively synthesized in four steps in 13% overall yield from commercially available 4,4'-diiodobiphenyl by using mono-I-Sn exchange, Sn-Pt transmetalation, I-Pd exchange, and subsequent oxidative coupling reactions. The single-crystal X-ray structure of [10]CPP is described. 相似文献
40.
In information theory, lossless compression of general data is based on an explicit assumption of a stochastic generative model on target data. However, in lossless image compression, researchers have mainly focused on the coding procedure that outputs the coded sequence from the input image, and the assumption of the stochastic generative model is implicit. In these studies, there is a difficulty in discussing the difference between the expected code length and the entropy of the stochastic generative model. We solve this difficulty for a class of images, in which they have non-stationarity among segments. In this paper, we propose a novel stochastic generative model of images by redefining the implicit stochastic generative model in a previous coding procedure. Our model is based on the quadtree so that it effectively represents the variable block size segmentation of images. Then, we construct the Bayes code optimal for the proposed stochastic generative model. It requires the summation of all possible quadtrees weighted by their posterior. In general, its computational cost increases exponentially for the image size. However, we introduce an efficient algorithm to calculate it in the polynomial order of the image size without loss of optimality. As a result, the derived algorithm has a better average coding rate than that of JBIG. 相似文献