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991.
The absolute configuration of phomopsidin, a marine-derived fungal metabolite from Phomopsis sp. isolated at Pohnpei, was determined by the exciton chirality method as 6S, 7S, 8S, 11S, 12R, and 15R. The biosynthetic study using 13C-labeled precursors revealed the origin of all carbon atoms in phomopsidin, which was built by nine acetates and three methyl groups from l-methionine. Inhibitory activities of phomopsidin and its Me ester derivative against microtubule assembly were examined together with the structurally related compounds MK8383, solanapyrones, and tanzawaic acids. Phomopsidin and its (16Z)-isomer (MK8383) showed anti-microtubule activity at IC50 of 5.7 and 8.0 μM, respectively, while the Me ester and other compounds were not active at 100 μM. 相似文献
992.
Ichimura K Matsuda H Nakanishi H Kobayashi T 《Physical review. B, Condensed matter》1993,47(11):6250-6255
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Ishibashi H Kobayashi T Nakashima S Tamura O 《The Journal of organic chemistry》2000,65(26):9022-9027
Bu(3)SnH-mediated aryl radical cyclization onto methylenecycloalkanes having a phenylthio, an ester, or a nitrile group at the terminus of the alkenic bond provides exclusively exo cyclization products. The results are in sharp contrast to those reported for nonsubstituted methylenecycloalkanes, which give exclusively endo cyclization products. Formation of endo cyclization products has been suggested to be a result of a consecutive 5-exo cyclization of an aryl radical and neophyl rearrangement. The exo-selective aryl radical cyclization offers a new method for synthesizing fused aromatic compounds containing a benzylic quaternary carbon atom. 相似文献
998.
When the photoscintillo-roentgenography is used for relating the scintigram of internal organs to the anatomic structures, this method is found to have some defects--the difference of magnification between the emission scan and the roentgenogram, the inaccuracy due to the geometric distortion of the X-ray image, the impossibility of the simultaneous photographing of the scan and the X-rays, etc. Then, to diminish the influence of these defects we improved on the photographic recording system of a dual-heal scanner, and made use of the transmission scanning method. That is, we combined the recording parts, Ch1 and Ch2, into one system, using Ch1 for the light source of transmission scan and Ch2 for that of emission scan. In this way, we managed to make the two incident rays from those light sources converge into a focus upon a film. Thus we could perform a simultaneous emission-transmission scanning, by moving, at the same time in the same direction, the scanning detector over the patient and the small radioactive source (241Am) under him. This method can be applied to any radioactive nuclide to be used in transmission scanning and emission scanning. As the result of applying this method clinically in our department, the method has proved to be very useful for anatomic localization. 相似文献
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Kanazawa Y Tsuchiya Y Kobayashi K Shiomi T Itoh J Kikuchi M Yamamoto Y Nishiyama H 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,12(1):63-71
New asymmetric conjugate reduction of beta,beta-disubstituted alpha,beta-unsaturated ketones and esters was accomplished with alkoxylhydrosilanes in the presence of chiral rhodium(2,6-bisoxazolinylphenyl) complexes in high yields and high enantioselectivity. (E)-4-Phenyl-3-penten-2-one and (E)-4-phenyl-4-isopropyl-3-penten-2-one were readily reduced at 60 degrees C in 95 % ee and 98 % ee, respectively, by 1 mol % of catalyst loading. (EtO)2MeSiH proved to be the best hydrogen donor of choice. tert-Butyl (E)-beta-methylcinnamate and beta-isopropylcinnamate could also be reduced to the corresponding dihydrocinnamate derivatives up to 98 % ee. 相似文献