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排序方式: 共有238条查询结果,搜索用时 31 毫秒
1.
Giovanni Cerioni Costantino Floris Giaime Marongiu Gabriele Navarra Francesca Sotgiu 《Journal of heterocyclic chemistry》1994,31(5):1151-1155
1-5-benzoxathiepine compounds are a novel class of heterocyclic rings that present interesting properties as central nervous system depressants. With the aim to contribute to the elucidation of the structure-activity relationship of this class of compounds we report a structural study of the 3-hydroxy-1,5-benzoxathiepine both in solution and in the solid state. Studies by dynamic 13C-nmr in solution show that three conformations are possible for the oxathiepin ring. A unique chair conformation characterizes the atoms in the oxathiepine ring of the crystallized molecule. The crystal structure was solved by direct methods. Values of bond distances and angles are within the expected range. 相似文献
2.
R. Arnaldi R. Averbeck K. Banicz J. Castor B. Chaurand C. Cicalo A. Colla P. Cortese S. Damjanovic A. David A. De Falco A. Devaux A. Drees L. Ducroux H. En’yo A. Ferretti M. Floris A. Foerster P. Force N. Guettet A. Guichard H. Gulkanian J. Heuser M. Keil L. Kluberg J. Lozano C. Lourenço F. Manso A. Masoni P. Martins A. Neves H. Ohnishi C. Oppedisano P. Parracho P. Pillot G. Puddu E. Radermacher P. Ramalhete P. Rosinsky E. Scomparin J. Seixas S. Serci R. Shahoyan P. Sonderegger H.J. Specht R. Tieulent G. Usai R. Veenhof H.K. Wöhri 《The European Physical Journal C - Particles and Fields》2007,49(1):235-241
The NA60 experiment at the CERN SPS has studied low-mass muon pairs in 158 A GeV In–In collisions. A strong excess of pairs
is observed above the yield expected from neutral meson decays. The unprecedented sample size close to 400000 events and the
good mass resolution of about 2% made it possible to isolate the excess by subtraction of the decay sources. The shape of
the resulting mass spectrum shows some non-trivial centrality dependence, but is largely consistent with a dominant contribution
from π+π-→ϱ→μ+μ- annihilation. The associated ϱ spectral function exhibits considerable broadening, but essentially no shift in mass. The
pT-differential mass spectra show the excess to be much stronger at low pT than at high pT. The results are compared to theoretical model predictions; they tend to rule out models linking hadron masses directly to
the chiral condensate.
PACS 25.75.-q; 12.38.Mh; 13.85.Qk 相似文献
3.
Wijdeven MA Botman PN Wijtmans R Schoemaker HE Rutjes FP Blaauw RH 《Organic letters》2005,7(18):4005-4007
The stereoselective total synthesis of the novel quinolizidine alkaloid (+)-epiquinamide is presented, starting from the amino acid l-allysine ethylene acetal. Key steps in the synthesis involved a highly diastereoselective N-acyliminium ion allylation and a ring-closing metathesis reaction to provide the bicyclic skeleton. [reaction: see text] 相似文献
4.
Floris P. J. T. Rutjes Henk Hiemstra Hendrik H. Mooiweer W. Nico Speckamp 《Tetrahedron letters》1988,29(52):6975-6978
Acid catalyzed cyclization of methoxymethyl substituted acyclic hydrazides 4 provides cyclic hydrazides 5 in moderate to good yields through the intermediacy of N,N′-di(methoxycarbonyl)hydrazinium intermediates. 相似文献
5.
6.
Summary We describe a large class of one-parameter families , {}, , of two-dimensional diffeomorphisms which arestable for <0, exhibit acycle for =0, and thereafter have a bifurcation set of positive but arbitrarily smallrelative measure for in small intervals [0, ]. A main assumption is that the basic sets involved in the cycle havelimit capacities that are not too large.The second author acknowledges hospitality and financial support from IMPA/CNPq during the period this paper was prepared 相似文献
7.
20 lactating ewes were allotted to two groups: 10 subjects received orally 100 mg/day of CdCl2 for 108 consecutive days, and the remaining 10 acted as control. Reproductive performance in ewes and cadmium tissue accumulation, both in ewes and their lambs, were investigated. The results showed that in ewes: 1) the regular cadmium intestinal intake negatively influences all reproductive parameters; 2) cadmium is particularly accumulated in kidney and liver, but also in mammary gland, although at a distinctly lower level; 3) chronic administration does not increase cadmium placental transfer in lactating pregnant subjects. 相似文献
8.
Jorge M.M. Verkade Peter J.L.M. Quaedflieg Floris L. van Delft 《Tetrahedron letters》2006,47(46):8109-8113
Mild and efficient procedures for deprotection of the amine nitrogen protecting p-methoxyphenyl (PMP) group are described. Periodic acid and trichloroisocyanuric acid (TCCA) were found to be particularly effective in realizing amine liberation using 1 and 0.5 equiv of the oxidant, respectively. Extension of the periodic acid-mediated conditions to simultaneous alcohol oxidation by combination with a catalytic amount of sodium dichromate led to smooth conversion of PMP-protected Mannich products into the corresponding β-amino acids in a one-pot procedure. 相似文献
9.
Ruhal Floris 《Rendiconti del Circolo Matematico di Palermo》1980,29(2):291-302
In this paper we study gometrical conditions on the border of an open setX inC n that nullify some cohomological groups with values in the sheaf {ie291-1} of holomorphic functions. This attempt to define a «geometric convexity» (see n. 4) does succeed only in a particular case (theorem 3), mainly because we use rather weak conditions and not the best techniques: however these ones are interesting for themselves (approximation with sets derived from coronae rather than from discs). 相似文献
10.
[reaction: see text] Both unsaturated proline derivatives and optically active tryptophan analogues have been obtained via Pd-catalyzed cyclization of aniline-containing acetylenic amino acids. The side chain length of the cyclization precursor determines which one of the two possible products will be formed. 相似文献