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241.
Isoda T Yamamura I Tamai S Kumagai T Nagao Y 《Chemical & pharmaceutical bulletin》2006,54(10):1408-1411
An orally active carbapenem L-084, which exhibits high bioavailability in humans, has a 1-(1,3-thiazolin-2-yl)azetidin-3-ylthio moiety at the C-2 position of the 1beta-methylcarbapenem skeleton. We established a practical and cost-effective synthesis of 3-mercapto-1-(1,3-thiazolin-2-yl)azetidine (1) for further scale-up production of L-084. This synthesis method entails an industry-oriented reaction of azetidine ring-closure to yield N-benzyl-3-hydroxyazetidine (16), which is eventually converted to 1 via key intermediates, Bunte salts 19 and 20. 相似文献
242.
Chemoenzymatic synthesis of sacranosides a and B 总被引:1,自引:0,他引:1
Direct beta-glucosidation between (-)-myrtenol and nerol and D-glucose (3) using the immobilized beta-glucosidase from almonds with the synthetic prepolymer ENTP-4000 gave myrtenyl O-beta-D-glucoside (4) and neryl O-beta-D-glucoside (10), respectively. The coupling of the myrtenyl or neryl O-beta-D-glucopyranoside congeners (7 or 13) and 2,3,4-tri-O-benzoyl-beta-L-arabinopyranosyl bromide (8) afforded the coupled products (9 or 14), respectively. Deprotection of the coupled products (9 or 14) afforded the synthetic myrtenyl 6-O-alpha-L-arabinopyranosyl-beta-D-glucopyranoside (Sacranoside A, 1) or neryl 6-O-alpha-L-arabinopyranosyl-beta-D-glucopyranoside (Sacranoside B, 2), respectively. 相似文献
243.
Isoda T Hayashi K Tamai S Kumagai T Nagao Y 《Chemical & pharmaceutical bulletin》2006,54(11):1616-1619
The tandem and stepwise Staudinger/aza-Wittig reactions of several azides were examined in detail. The tandem reaction method (Method I) exhibited superior results in the yield of the corresponding isothiocyanates bearing an electron-withdrawing group than the conventional stepwise method (Method II) which involves the sequential treatment of the azides with triphenylphosphine and then carbondisulfide. The mechanistic consideration for both reaction methods was proposed on the basis of the 1H-NMR analyses. 相似文献
244.
Shindo M Kita T Kumagai T Matsumoto K Shishido K 《Journal of the American Chemical Society》2006,128(4):1062-1063
We have developed the E-selective olefination of ester carbonyls to afford tetrasubstituted, functionalized olefins and the C-S insertion of thiol esters to give beta-keto thiol esters via ynolates. 相似文献
245.
246.
K. Kuge N. Yasuda H. Kumagai K. Nakazawa T. Kobayashi N. Aoki A. Hasegawa 《Radiation measurements》2001,34(1-6):203-206
A photographic colour film, which was exposed to heavy ions, reveals a coloured dye image of the ion tracks. Since the colour film consists of several layers and different colours appear on each layer, three-dimensional information on the tracks in the layers can be obtained by the colour image. Previously, we have reported the method for which the tracks in different colours represented differences of track depth and we also discussed the disadvantages of using commercial colour films. Here we present the procedure for a self-made photographic coating and the development formula which can overcome the disadvantages. 相似文献
247.
A fractal field is a collection of fractals with, in general, different Hausdorff dimensions, embedded in 2. We will construct diffusion processes on such fields which behave as Brownian motion in 2 outside the fractals and as the appropriate fractal diffusion within each fractal component of the field. We will discuss the properties of the diffusion process in the case where the fractal components tile 2. By working in a suitable shortest path metric we will establish heat kernel bounds and large deviation estimates which determine the trajectories followed by the diffusion over short times. 相似文献
248.
Saito T Maruyama R Ono S Yasukawa N Kodaira K Nishizawa M Ito S Inoue M 《Applied biochemistry and biotechnology》2003,111(3):185-190
Benzil (1) was selectively reduced to (S)-benzoin (2) in the presence of a wild-type Bacillus cereus Tim-r01. A 92% yield of 2 with 94% enantiomeric excess ratio was attained in phosphate-buffered saline (PBS) (pH 7.5) by using glucose as a nutrient at 37 degrees C for 12 h. Compound 2 was not reduced further to hydrobenzoin (3) at all. The reduction activity differed greatly depending on the strain of B. cereus. Under these conditions the B. cereus strains IFO3001, IFO15305, IAM1110, IAM1229, IAM1656, and IAM1729 gave 2 in yields ranging from 23 to 46% and the configuration of 2 was (S)-form (7 to 86% ee). 相似文献
249.
250.
Tsutomu Kumagai Takumi Nittono Noriyuki Tanaka Toshio Mukai 《Tetrahedron letters》1985,26(49):6093-6096
Upon irradiation, 2-dicyanomethylenebenzonorbornene f was converted into 1-dicyanomethylenebenzobicyclo[3.1.1]heptene . The reaction pathway is discussed with reference to the photoreaction of parent hydrocarbon. 相似文献