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221.
Formate dehydrogenase (FDH)–viologen with a long alkyl chain (CH3V(CH2) n COOH) immobilized on an indium–tin oxide (ITO) electrode, with the function of reduction of CO2 to formic acid, was investigated as an artificial photosynthesis device based on CO2 reduction. The amount of formic acid produced by use of FDH–CH3V(CH2) n COOH immobilized on ITO in CO2-saturated buffer solution, on application of a potential, as a result of one-electron reduction of viologen, depends on the carbon chain length of CH3V(CH2) n COOH. When a CH3V(CH2)9COOH–FDH/ITO electrode was used, production of formic acid was estimated to be 23 μmol after 3 h. 相似文献
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223.
We hypothesized that, because the stereoselectivity of anomeric radical reactions was significantly influenced by the anomeric effect, which can be controlled by restricting the conformation of the radical intermediate, the proper conformational restriction of the pyranose ring of the substrates would therefore make highly alpha- and beta-stereoselective anomeric radical reactions possible. Thus, the conformationally restricted 1-phenylseleno-D-xylose derivatives 9 and 10, restricted in a (4)C(1)-conformation, and 11 and 12, restricted in a (1)C(4)-conformation, were designed and synthesized by introducing the proper protecting groups on the hydroxyl groups on the pyranose ring as model substrates for the anomeric radical reactions. The radical deuterations with Bu(3)SnD and the C-glycosylation with Bu(3)SnCH(2)CH [double bond] CH(2) or CH(2) [double bond] CHCN, using the (4)C(1)-restricted substrates 9 and 10, afforded the corresponding alpha-products (alpha/beta = 97:3-85:15) highly stereoselectively, whereas the (1)C(4)-restricted substrates 11 and 12 selectively gave the beta-products (alpha/beta = 1:99-0:100). Thus, stereoselectivity was significantly increased by conformational restriction and was completely inverted by changing the substrate conformation from the (4)C(1)-form into the (1)C(4)-form. Ab initio calculations suggested that the radical intermediates produced from these substrates possessed the typical (4)C(1)- or (1)C(4)-conformation, which was similar to that of the substrates, and that the anomeric effect in these conformations would be the factor controlling the transition state of the reaction. Therefore, the highly alpha- and beta-selective reactions would occur because of the anomeric effect, which could be manipulated by conformational restriction of the substrates, as expected. This would be the first radical C-glycosylation reaction to provide both alpha- and beta-C-glycosides highly stereoselectively. 相似文献
224.
S Shuto N Shibuya S Yamada T Ohkura R Kimura A Matsuda 《Chemical & pharmaceutical bulletin》1999,47(8):1188-1192
Conformationally restricted analogs of baclofen (2), i.e., 5, 6, and their enantiomers ent-5, and ent-6, the conformations of which were restricted by introducing a cyclopropane ring, were designed as potential GABAB receptor ligands. Reaction of (R)-epichlorohydrin [(R)-7] and (4-chlorophenyl)acetonitrile in the presence of NaNH2 in benzene/tetrahydrofuran gave chiral cyclopropane derivatives 11 and 12, which were then converted into the target compounds 5 and 6, respectively. Their corresponding enantiomers, ent-5 and ent-6, were also synthesized starting from (S)-epichlorohydrin [(S)-7]. 相似文献
225.
Makoto Eishima Shigeru Ohba Masumi Suzuki Chiaki Nagasawa Takeshi Sugai 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(11):1391-1393
In the racemic crystals of (1S,2R)‐ or (1R,2S)‐1‐[N‐(chloroacetyl)carbamoylamino]‐2,3‐dihydro‐1H‐inden‐2‐yl chloroacetate, C14H14Cl2N2O4, (I), the enantiomeric molecules form a dimeric structure via the N—H?O cyclic hydrogen bond of the carbamoyl moieties. In the chiral crystals of (—)‐(1S,2R)‐1‐[N‐(chloroacetyl)carbamoylamino]‐2,3‐dihydro‐1H‐inden‐2‐yl chloroacetate, C14H14Cl2N2O4, (II), the N—H?O intermolecular hydrogen bond forms a zigzag chain around the twofold screw axis. The melting points and calculated densities of (I) and (II) are 446 and 396 K, and 1.481 and 1.445 Mg m?3, respectively. 相似文献
226.
Tsutomu Shinzawa Fumihiko Uesugi Iwao Nishiyama Kazumi Sugai Shunji Kishida Hidekazu Okabayashi 《应用有机金属化学》2000,14(1):14-24
A new type of precursor for aluminum chemical vapor deposition (Al‐CVD) has been developed by mixing dimethylaluminum hydride (DMAH) and trimethylaluminum (TMA). The new precursor has proven itself to be effective for Al‐CVD, where a good selectivity between the Si and the SiO2 mask, a 3.0 μΩ cm resistivity and a pure Al film with low C and O contamination levels (under 100 ppm) were achieved. Quadrupole mass and infrared absorption analysis have shown that the precursor contains a new molecular compound, consisting of a DMAH monomer and a TMA monomer. The mixture has lower viscosity than DMAH and can be easily bubbled for a stable precursor vapor supply. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
227.