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31.
We present the study of exact inhomogeneous cosmological solutions to a four-dimensional low energy limit of string theory
containing non-minimal interacting electromagnetic, dilaton and axion fields. We focus at Einstein-Rosen solutions of Einstein-Maxwell-dilaton-axion
equations. Several cases are analyzed and some of them have asymptotically velocity-term dominated (AVTD) singularities. 相似文献
32.
Anatol P. Spork Stefan Koppermann Birger Dittrich Regine Herbst-Irmer Christian Ducho 《Tetrahedron: Asymmetry》2010,21(7):763-766
The reaction of protected uridine 5′-aldehydes with sulfur ylides has been reinvestigated. Further transformation of the resulting epoxide product provided a compound of which a single crystal for X-ray diffraction was obtained. As a consequence from the elucidated structure, the stereochemical configuration of the epoxide furnished by the sulfur ylide reaction was revised. Based on these results, an efficient synthesis of the core structure of the naturally occurring muraymycin and caprazamycin nucleoside antibiotics was developed. 相似文献
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35.
E. Maurer F. Hartmann F. Mylius F. Foerster G. Schoene H. Schenck Alexander Fischer G. T. Dougherty M. Dittrich A. Leonhard O. L. Barnebey J. V. Mc Crae R. L. Dowdell L. Jordan J. G. Thompson J. S. Acken J. H. S. Dickenson P. Herasymenko G. Pondélik Th. R. Cunningham R. J. Price C. H. Herty G. R. Fitterer J. E. Eckel J. J. Egan W. Crafts und A. B. Kinzel 《Fresenius' Journal of Analytical Chemistry》1935,101(1-2):50-53
Ohne Zusammenfassung 相似文献
36.
Ohne Zusammenfassung 相似文献
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38.
Lamellarin K is a complex pyrrole natural product and member of the lamellarin family – a group of natural products known for their potent biological activities, such as, antiproliferative activity and inhibition of P-gp mediated drug efflux pumps. We herein describe the synthesis of the N-benzyl-des-D ring analogue of lamellarin K using a route that centres on an acyl-Claisen reaction to eventually prepare a highly-functionalised 1-aryl-4-methyl-1,4-diketone. Paal-Knorr pyrrole formation using this diketone undergoes auto-oxidation to give a fully-substituted 5-formyl pyrrole which was converted into the natural lactone B ring. Antiproliferative testing of the N-benzyl-des-D ring analogue gave an IC50 of 2.63 μM against the MDA-MB-231 breast cancer cell line. 相似文献
39.
Dennis Dittrich Heiko Tewes Christoph Wölper Dieter Bläser Stephan Schulz Joachim Roll 《Transition Metal Chemistry》2017,42(3):237-241
Reaction of [Zn4(µ4-O)(O2CCH3)6] with one equivalent of 4-tertiary-butylpyridine leads to a nearly quantitative formation of the heptanuclear cluster [Zn7O2(O2CCH3)10(tbupy)2] (1). Here, we present the crystal structure of 1 and first results of the examination of its catalytic activity in transesterification reactions and polymerization of lactide compared to the activity of [Zn4(µ4-O)(O2CCH3)6] in the presence of 4-tertiary-butylpyridine. 相似文献
40.
<正>A new practical method for the synthesis of unsymmetrical ureas was achieved by reaction of phenylurea with primary and secondary amines under neutral and mild condition in very good yields.The reaction took place in refluxing dioxane and does not require any catalyst or additives. 相似文献