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991.
Nicolas Soldermann Joerg Velker Olivier Vallat Helen Stoeckli‐Evans Reinhard Neier 《Helvetica chimica acta》2000,83(9):2266-2276
The novel tandem process Diels‐Alder reaction/Ireland‐Claisen rearrangement shows a high diastereoselectivity for the Ireland‐Claisen rearrangement starting from the endo‐product of the Diels‐Alder reaction. Based on this mechanistic knowledge, the novel tandem process could be applied to the synthesis of rac‐juvabione. 相似文献
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993.
994.
K. C. Nicolaou Jinyou Xu Fiona Murphy Sofia Barluenga Olivier Baudoin Heng-xu Wei David L. F. Gray Takashi Ohshima 《Angewandte Chemie (International ed. in English)》1999,38(16):2447-2451
The immunosuppressive agent sanglifehrin A has been prepared for the first time by total synthesis. The construction of the macrocyclic unit of the target molecule was achieved through a selective intramolecular Stille coupling, and the spirolactam unit by Paterson–aldol reactions. The final steps involve an intermolecular Stille coupling and the opening of the internal acetal unit. This convergent synthesis opens the way for the synthesis of libraries of novel sanglifehrin analogues for biological screening. 相似文献
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997.
Olivier Legrand Jean Michel Brunel Grard Buono 《Angewandte Chemie (International ed. in English)》1999,38(10):1479-1483
An addition-pseudorotation-elimination pathway is proposed for the first stereospecific ring-expansion reaction of chiral diazaphospholidine oxides by a 1,3-migration of P from N to C [Eq. (1)]. R=H, Ph; LDA=lithium diisopropylamide. 相似文献
998.
Thomas X. Neenan Matthew R. Callstrom Olivier J. A. Schueller 《Macromolecular Symposia》1994,80(1):315-322
We describe the synthesis and characterization of metallopolymers comprising poly(phenylene diacetylenes) containing platinum and cobalt species coordinated to the triple bonds of the diacetylene moities. Thermal treatment of these polymers as thin films results in their conversion to hetero glassy carbon (HGC). The coordinated metals are retained within the matrices of the glassy carbons as small metallic clusters (∼10-30 Å for Pt and 50-1000 Å for cobalt). The platinum doped glassy carbon shows remarkable activity for the reduction of both H+ and O2, a result that has important implications for the development of fuel cell electrodes. At both pH 0 and 7, the platinum Pt-HGC reduced the overpotential for O2 reduction by ∼800 mV, and resulted in a voltammetric response similar to that of pure platinum. 相似文献
999.
The global response of polycrystalline aggregates is investigated, in order to simulate grain size effects in IF ferritic steels. The mechanics of generalized continua is used to describe the studied phenomena. The polycrystal is regarded as a heterogeneous Cosserat medium, and the overall properties are estimated using a specific homogenization technique. To illustrate the capabilities of the model, some simple bidimensionnal computations are presented for different grain sizes. Afterwards tridimensionnal computations are shown in order to extract the global effect on the mechanical behaviour for grain sizes ranging from 5 µm to 120 µm. The finite element response is harder for the smallest grain size, but the model still underestimate the grain size effect on the tensile response. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
1000.
Andr Deluzet Olivier Guillou 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(7):m277-m279
The title compound is composed of one‐dimensional polymeric {[Er2(C12O12)(H2O)10]·4H2O}n chains containing Er in a slightly distorted antiprismatic eightfold coordination. The benzenehexacarboxylate ion is located about an inversion centre. Water molecules of crystallization, linked by hydrogen bonding to water molecules of the rare earth coordination spheres or the carboxylate groups of the organic ligands, fill the space generated by the packing of the separated chains. 相似文献