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941.
By means of the CHEVENARD thermobalance, the authors have traced the curve of pyrolysis of the following strontium compounds; sulphate, fluoride, iodate, arsenate, carbonate, chromate, oxalate and tartrate. They have determined the temperatures at which the dissociation of the sulphate and chromate begins to occur. They recommend as excellent the weighing of strontium in the form of the iodate and para periodate. 相似文献
942.
943.
The abstract boundary M of a normal complex-analytic surface singularity is canonically equipped with a contact structure. We show that if M is a rational homology sphere, then this contact structure is uniquely determined by the topological type of M. An essential tool is the notion of open book carrying a contact structure, defined by E. Giroux. To cite this article: C. Caubel, P. Popescu-Pampu, C. R. Acad. Sci. Paris, Ser. I 339 (2004). 相似文献
944.
Cl. Winkler 《Fresenius' Journal of Analytical Chemistry》1871,10(1):238-244
Ohne Zusammenfassung 相似文献
945.
Dr. Guillaume Despras Clémence Bernard Anthony Perrot Laurent Cattiaux Prof. Alain Prochiantz Dr. Hugues Lortat‐Jacob Dr. Jean‐Maurice Mallet 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(2):531-540
Chondroitin sulfate‐E (CS‐E) oligosaccharidic analogues (di to hexa) were prepared from lactose. In these compounds, the 2‐acetamido group was replaced by a hydroxyl group. This modification speeded up the synthesis, and large oligosaccharides were constructed in a few steps from a lactose‐originated block. The protecting groups used were as follows; Fmoc for hydroxyl groups to be glycosylated, allyl group for anomeric position protection, and trichoroacetimidate leaving groups were used to prepare up to octasaccharides. We took advantage of the presence of allyl group to develop a click biotinylation, through its transformation into a 3‐azido‐2‐hydroxyl propyl group in two steps (epoxidation and sodium azide epoxide opening). The biotinylating agent was a water‐soluble propargylated and biotinylated triethylene glycol (PEG). By using surface plasmon resonance (SPR), it was shown that the di‐, tetra‐, and hexasaccharides display a binding affinity and selectivity toward HSF/GSF and CXCL12 similar to that of CS‐E. A parallel study confirmed their mimicry of natural compounds, based on the hexasaccharide interaction with Otx2, a homeodomain protein involved in brain maturation, thus validating our simplification approach to synthesize bioactive GAG. 相似文献
946.
Highly Modular C1‐Symmetric Chiral (P,N) Ligands with a Stereolabile P Center: Experimental and Theoretical Studies
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Nicolas Humbert Dr. Evgeny Larionov Luca Mantilli Pradeep Nareddy Dr. Céline Besnard Dr. Laure Guénée Prof. Dr. Clément Mazet 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(3):745-751
An improved synthesis of a novel class of bidentate (P,N) ligands is presented, the structures of which are characterized by three distinct elements of chirality. The stereoselective installation of the elements of central chirality (at the benzylic carbon and the phosphorus atom) depends on the size of the phosphorus substituent. Thermal inversion of the phosphorus center has been studied experimentally and further correlated by DFT calculations. The potential of these ligands and the role of the phosphorus atom in the asymmetric α‐arylation of aldehydes (Pd) and hydrogenation of allylic alcohols (Ir) have also been investigated. 相似文献
947.
Ligand‐Controlled Regiodivergent Pathways of Rhodium(III)‐Catalyzed Dihydroisoquinolone Synthesis: Experimental and Computational Studies of Different Cyclopentadienyl Ligands
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Dr. Matthew D. Wodrich Baihua Ye Dr. Jérôme F. Gonthier Prof. Dr. Clémence Corminboeuf Prof. Dr. Nicolai Cramer 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(47):15409-15418
RhIII‐catalyzed directed C?H functionalizations of arylhydroxamates have become a valuable synthetic tool. To date, the regioselectivity of the insertion of the unsaturated acceptor into the common cyclometalated intermediate was dependent solely on intrinsic substrate control. Herein, we report two different catalytic systems that allow the selective formation of regioisomeric 3‐aryl dihydroisoquinolones and previously inaccessible 4‐aryl dihydroisoquinolones under full catalyst control. The differences in the catalysts are computationally examined using density functional theory and transition state theory of different possible pathways to elucidate key contributing factors leading to the regioisomeric products. The stabilities of the initially formed rhodium complex styrene adducts, as well as activation barrier differences for the migratory insertion, were identified as key contributing factors for the regiodivergent pathways. 相似文献
948.
An efficient and stereoselective three step synthesis of (+)-α-cyperone 1 is described. The key step involves an stereoselective Michael addition of chiral imine to (R)-dihydrocarvone. 相似文献
949.