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221.
222.
Prof. Dr. Shinichiro Fuse Keiji Komuro Dr. Yuma Otake Dr. Hisashi Masui Prof. Dr. Hiroyuki Nakamura 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(27):7525-7532
Lactams are cyclic amides that are indispensable as drugs and as drug candidates. Conventional lactamization includes acid-mediated and coupling-agent-mediated approaches that suffer from narrow substrate scope, much waste, and/or high cost. Inexpensive, less-wasteful approaches mediated by highly electrophilic reagents are attractive, but there is an imminent risk of side reactions. Herein, a methods using highly electrophilic triphosgene in a microflow reactor that accomplishes rapid (0.5–10 s), mild, inexpensive, and less-wasteful lactamization are described. Methods A and B, which use N-methylmorpholine and N-methylimidazole, respectively, were developed. Various lactams and a cyclic peptide containing acid- and/or heat-labile functional groups were synthesized in good to high yields without the need for tedious purification. Undesired reactions were successfully suppressed, and the risk of handling triphosgene was minimized by the use of microflow technology. 相似文献
223.
Natsumi Koga Dr. Masaru Tanioka Prof. Dr. Shinichiro Kamino Prof. Dr. Daisuke Sawada 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(11):3761-3765
Superior pH-responsive molecules are required for the development of functional materials applicable to advanced molecular technologies. Despite having been widely developed, many rhodamine-based pH-responsive molecules exhibit a single configurational switch for “turn-on”. Herein, we report a new type of rhodamine-based pH-responsive molecule with multi-configurational switches displaying stable two-step structural and color conversion in response to pH. This rhodamine analogue could be successfully applied to optical sensing of pH gradient under extreme acidic environments both in solution and on hydrogel through high-contrast color change. We demonstrated that this multi-responsive character enabled optical memory of different pH information. 相似文献
224.
225.
Toshitaka Okamura Dr. Syusuke Egoshi Dr. Kosuke Dodo Prof. Dr. Mikiko Sodeoka Prof. Dr. Yoshiharu Iwabuchi Prof. Dr. Naoki Kanoh 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(70):16002-16006
Despite the potential of α-fluoroethers in medicinal chemistry, their synthetic methods, especially etherification of aliphatic alcohols, have been limited. Herein, we developed two- and three-step gem-difluoropropargylation of aliphatic alcohols including amino acid derivatives and naturally occurring bioactive molecules. Highly chemoselective etherification proceeded by using the gem-difluoropropargyl bromide dicobalt complex in the presence of silver triflate and triethylamine. Decomplexation of dicobalt complexes was achieved by using cerium ammonium nitrate or N,N,N′-trimethylethylenediamine. The thus obtained gem-difluoropropargyl ethers were converted to various α-difluoroethers which are expected to be useful for medicinal chemistry. 相似文献
226.
Asymmetric Total Synthesis of Heronamides A–C: Stereochemical Confirmation and Impact of Long‐Range Stereochemical Communication on the Biological Activity
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Prof. Dr. Naoki Kanoh Shunya Itoh Kohei Fujita Dr. Kohei Sakanishi Ryosuke Sugiyama Yuta Terajima Prof. Dr. Yoshiharu Iwabuchi Prof. Dr. Shinichi Nishimura Prof. Dr. Hideaki Kakeya 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(25):8586-8595
Heronamides are biosynthetically related metabolites isolated from marine‐derived actinomycetes. Heronamide C shows potent antifungal activity by targeting membrane phospholipids possessing saturated hydrocarbon chains with as‐yet‐unrevealed modes of action. In spite of their curious hypothesized biosynthesis and fascinating biological activities, there have been conflicts in regard to the reported stereochemistries of heronamides. Here, we describe the asymmetric total synthesis of the originally proposed and revised structures of heronamide C, which unambiguously confirmed the chemical structure of this molecule. We also demonstrated nonenzymatic synthesis of heronamides A and B from heronamide C, which not only proved the postulated biosynthesis, but also confirmed the correct structures of heronamides A and B. Investigation of the structure–activity relationship of synthetic and natural heronamides revealed the importance of both long‐range stereochemical communication and the 20‐membered macrolactam ring for the biological activity of these compounds. 相似文献
227.
Taiki Morita Somaraju Yugandar Shinichiro Fuse Hiroyuki Nakamura 《Tetrahedron letters》2018,59(13):1159-1171
Isoxazole is an important pharmacophore that is critical for biological activity. The isoxazole ring ranks 33rd in frequency among the 351 ring systems found in marketed drugs, thus suggesting a great deal of interest in the synthesis of functional isoxazoles. In recent years, various approaches have been developed for the synthesis and functionalization of isoxazoles. This comprehensive survey summarizes the recent new synthetic approaches to functionalized isoxazoles, with particular focus on the last three years with regard to the following reaction types: (1) 1,3-dipolar cycloaddition, (2) condensation, (3) cycloisomerization, and (4) direct functionalization. 相似文献
228.
Yoshihiko Ooka Fumihiko Kanai Shinichiro Okabe Takuya Ueda Ryota Shimofusa Sadahisa Ogasawara Tetsuhiro Chiba Yasunori Sato Masaharu Yoshikawa Osamu Yokosuka 《Magnetic resonance imaging》2013
Purpose
To assess the value of gadoxetic acid-enhanced magnetic resonance imaging (MRI) for the pre-therapeutic detection of hepatocellular carcinoma (HCC) using receiver operating characteristic (ROC) analysis with the combination of computed tomography (CT) arterial portography and CT hepatic arteriography (CTAP/CTHA).Materials and Methods
A total of 54 consecutive patients with 87 nodular HCCs were retrospectively analyzed. All HCC nodules were confirmed pathologically. Three blinded readers independently reviewed 432 hepatic segments, including 78 segments with 87 HCCs. Each reader read two sets of images: Set 1, CTAP/CTHA; Set 2, gadoxetic acid-enhanced MRI including a gradient dual-echo sequence and diffusion-weighted imaging (DWI). The ROC method was used to analyze the results. The sensitivity, specificity, positive predictive value, negative predictive value and sensitivity according to tumor size were evaluated.Results
For each reader, the area under the curve was significantly higher for Set 2 than for Set 1. The mean area under the curve was also significantly greater for Set 2 than for Set 1 (area under the curve, 0.98 vs. 0.93; P = .0009). The sensitivity was significantly higher for Set 2 than for Set 1 for all three readers (P = .012, .013 and .039, respectively). The difference in the specificity, positive predictive values and negative predictive values of the two modalities for each reader was not significant (P > .05).Conclusion
Gadoxetic acid-enhanced MRI including a gradient dual-echo sequence and DWI is recommended for the pre-therapeutic evaluation of patients with HCC. 相似文献229.
Yoshihiro Maruyama Masaru Joe Fuse Takeshi Yokomori Ryo Ohmura Shigeru Watanabe Toru Iwasaki Wataru Iwabuchi Toshihisa Ueda 《Proceedings of the Combustion Institute》2013,34(2):2131-2138
Flame spreading over pure methane hydrate in a laminar boundary layer is investigated experimentally. The free stream velocity (U∞) was set constant at 0.4 m/s and the surface temperature of the hydrate at the ignition (Ts) was varied between ?10 and ?80 °C. Hydrate particle sizes were smaller than 0.5 mm. Two types of flame spreading were observed; “low speed flame spreading” and “high speed flame spreading”. The low speed flame spreading was observed at low temperature conditions (Ts = ?80 to ?60 °C) and temperatures in which anomalous self-preservation took place (Ts = ?30 to ?10 °C). In this case, the heat transfer from the leading flame edge to the hydrate surface plays a key role for flame spreading. The high speed flame spreading was observed when Ts = ?50 and ?40 °C. At these temperatures, the dissociation of hydrate took place and the methane gas was released from the hydrate to form a thin mixed layer of methane and air with a high concentration gradient over the hydrate. The leading flame edge spread in this premixed gas at a spread speed much higher than laminar burning velocity, mainly due to the effect of burnt gas expansion. 相似文献
230.
Shinichiro Kamino Takako Yamaguchi Terumi Mori Mika Miyamoto Yukimi Kusumi Yoshikazu Fujita 《Analytical sciences》2005,21(12):1549-1552
A highly spectrophotometric method for the determination of aluminum was developed. This method used the color reaction between m-carboxyphenylfluorone (MCPF) as a novel chemical probe and aluminum in the presence of a surfactant, poly(N-vinylpyrrolidone) (PVP, K-90) (0.03 - 1.40 microg of aluminum in a final volume of 10 ml at 561 nm). The proposed method showed excellent sensitivity (molar absorptibity of 1.70 x 10(5) l mol(-1) cm(-1)) and reproducibility (within-day precision: RSD = 0.35% n = 6, between-day precision: RSD = 0.44% n = 6). Linearity was achieved over the range 3 - 140 microg L(-1) with a correlation coefficient of 0.9999, and the effects of foreign substances were low. 相似文献