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排序方式: 共有136条查询结果,搜索用时 218 毫秒
131.
Ronny Hesse Dr. Konstanze K. Gruner Dr. Olga Kataeva Dr. Arndt W. Schmidt Prof. Dr. Hans‐Joachim Knölker 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(42):14098-14111
We have developed a highly efficient route to 2‐hydroxy‐3‐methylcarbazole ( 1 ) via a palladium‐catalyzed construction of the carbazole skeleton. Using 1 as relay compound, different methods for annulations of pyran rings by reaction with terpenoid building blocks have been tested. The Lewis acid promoted reaction of 1 with prenal ( 21 ) opened up an efficient route to girinimbine ( 3 ) and the corresponding reaction with citral ( 25 ) afforded mahanimbine ( 5 ). Oxidation of compounds 3 and 5 provided murrayacine ( 4 ) and murrayacinine ( 6 ). Following the biogenetic proposal, mahanimbine ( 5 ) has been exploited for efficient biomimetic syntheses of the cyclized monoterpenoid pyrano[3,2‐a]carbazole alkaloids cyclomahanimbine ( 7 ), mahanimbidine ( 8 ) and bicyclomahanimbine ( 9 ). The interconversions of 5 , 7 , 8 and 9 are described and mechanistic implications are discussed. Structural assignments are unambiguously verified by X‐ray crystal structure determinations. Moreover, cyclomahanimbine ( 7 ) was transformed into murrayazolinine ( 10 ) and exozoline ( 11 ). 相似文献
132.
We describe the total synthesis of euchrestifoline featuring an unprecedented one-pot Wacker oxidation and double aromatic C-H bond activation. 相似文献
133.
Konstanze Rietsch 《Journal of the American Mathematical Society》2008,21(2):611-614
We make a correction to Remark 4.3 and the proof of Theorem 4.2 (Peterson's Theorem) which identifies with the coordinate ring of a certain affine stratum of the Peterson variety . Explicitly, we introduce additional coordinates to obtain a complete coordinate system on and then show that they lie in the defining ideal of the Peterson variety , hence play no role in the presentation of .
134.
Jens Hartung Irina Kempter Thomas Gottwald Michaela Schwarz Rainer Kneuer 《Tetrahedron: Asymmetry》2009,20(18):2097-2104
Esterification of cyclic thiohydroxamic acids, for example, N-hydroxypyridine-2(1H)-thione, N-hydroxy-4-methylthiazole-2(3H)-thione, and N-hydroxy-4-(p-chlorophenyl)-thiazole-2(3H)-thione, occurred with inversion of configuration at the attacked stereocenter, as evident from the use of chiral alcohols, alkyl p-toluene sulfonates, and cyclic sulfates. Stereochemical analysis of enantiomerically pure O-alkyl thiohydroxamates was performed on the basis of CD-spectroscopy and chemical derivatization. The assignment of the relative configuration in cyclic O-esters was feasible via NMR spectroscopy, whereas chiral aliphatic glycolato monoesters required hydroxyl group derivatization with chloro-(4R,5R)-bis[(1R,2S,5R)-menth-1-yloxycarbonyl)]-1,3,2-dioxaphospholane for this purpose. 相似文献
135.
We give a representation-theoretic proof of a conjecture from Rietsch (Adv Math 217:2401–2442, 2008) providing integral formulas for solutions to the quantum Toda lattice in general type. This result generalizes work of Givental
for SL
n
/B in a uniform way to arbitrary type, and can be interpreted as a kind of mirror theorem for the full flag variety G/B. We also prove the existence of a totally positive and totally negative critical point of the ‘superpotential’ in every mirror
fiber. 相似文献
136.
Frank Würthner Stefan Brse Norbert Sewald Rainer Herges Matthias O. Senge Thorsten Bach Thomas Gottwald Thomas Kopf Kristina pehar Jens Hartung Dietmar Plattner Andreas Gansuer Martin Oestreich Reinhard Brückner Jrg Pietruszka Roderick Süßmuth Michael Müller Elmar Weinhold Andres Jschke Markus Albrecht Henning Priepke Gerhard Roth Klaus Ditrich Alexander Ernst Lars Wortmann Schering Ag 《Nachrichten aus der Chemie》2003,51(3):286-315
Die enantioselektive Synthese bleibt zentrales Thema in metallorganischen, metallfreien and bioorganischen Transformationen sowie in der industriellen organischen Chemie. Glanzpunkte zielmolekülorientierter Synthesechemie waren ein Zugang zu C60, die Route zum Diazonamid A und die Totalsynthese von Vinblastin. Mit „Pyrrolysin”︁ wurde die 22. proteinogene Aminosäure entdeckt. Trotz der immer höheren Zahl an Testsubstanzen besteht in der medizinischen Chemie ein Engpass an klinisch erfolgreichen Wirkstoffen. 相似文献