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111.
In this paper we study theoretically the molecular structure of [Be(C5Me5)2], with special interest in similarities and differences found in the computed geometric parameters, depending on the treatment of the electron correlation used. Given the low energy differences found between the different configurations studied (less than 4 kcal mol−1), and the high fluxionality found in experimental studies for this compound, we analyzed the dynamics of the system by means of first principles molecular dynamics calculations. A complex dynamics is found and analyzed in terms of two molecular rearrangement processes: 1,2-sigmatropic intraring rearrangement and a ring inversion mechanism that interchanges the roles (with regard to their coordination to the central Be atom) of the two rings.Dedicated to Dr. Jeal Paul Malrieu on occasion of his 65th birthday. 相似文献
112.
[reaction: see text] The stereospecific alpha-lithiation of optically active styrene oxides and the trapping reaction of the corresponding highly reactive intermediates with electrophiles to produce optically active styrene oxide derivatives are described. This methodology has been applied to the synthesis of an optically active oral antifungal agent of industrial interest. 相似文献
113.
Marina DellaGreca Antonio FiorentinoMarina Isidori Lucio PreviteraFabio Temussi Armando Zarrelli 《Tetrahedron》2003,59(26):4821-4825
Investigation of the ethyl acetate extract of Juncus acutus rhizomes revealed seven benzocoumarins, probably derived from oxidation of phenanthrenes already isolated from the plant. The structures were determined by means of spectroscopic methods. The anti-algal activity of the isolated compounds tested on the green alga Pseudokirchneriella subcapitata are reported here. 相似文献
114.
115.
Antonio Cnovas Jesús Fonrodona Juan-Julio Bonet Marie Claire Brians Jos Luis Brians 《Helvetica chimica acta》1980,63(8):2380-2389
The UV. irradiation of 17 β-hydroxy-2-aza-4-androsten-3-one (1) , N-methyl-17 β-hydroxy-2-aza-4-androsten-3-one (3) , 17 β-hydroxy-4-aza-5 β-androst-1-en-3-one (2) and N-methyl-17 β-hydroxy-4-aza-5 β-androst-1-en-3-one (4) , gives rise to 1,10-seco (from 1 and 3 ) and 5, 10-seco (from 2 and 4 ) steroids. 相似文献
116.
Molecularly imprinted polymers (MIPs) are tailor-made synthetic polymers with a predetermined selectivity for a given analyte, or group of structurally related compounds, that make them ideal materials for use as stationary phases in affinity chromatography. However, extensive peak broadening and tailing, especially of the more retained compound (normally the template) are often observed. Thus, huge efforts have been made during recent years to use MIPs in capillary electrochromatography, which is inherently a more efficient chromatographic technique than conventional HPLC. Accordingly, this paper gives an overview of the attempts carried out in the recent past to improve the chromatographic performance of MIPs in capillary electrochromatography as well as more recent applications. It is concluded that MIPs are very promising materials for use as selective stationary phases in CEC. 相似文献
117.
118.
Let X be a complex projective manifold and AX a non-singular hypersurface which is an ample divisor having characteristic cycles Ai non-singular in every dimension i0. The pairs (X,A) such that g(A1)=h1,0 (X) are characterized. 相似文献
119.
Letizia JA Facchetti A Stern CL Ratner MA Marks TJ 《Journal of the American Chemical Society》2005,127(39):13476-13477
New carbonyl-functionalized quaterthiophenes, 5,5' '-diperfluorophenylcarbonyl-2,2':5',2' ':5' ',2' '-quaterthiophene [DFCO-4T], 5,5' '-diphenyl-2,2':5',2' ':5' ',2' '-quaterthiophene [DPCO-4T], and a polymer having the same basic motif as DFCO-4T, poly{1,4-bis[(3'-n-octyl-2,2'-dithiophene)carbonyl]-2,3,5,6-tetrafluorobenzene} [P(COFCO-4T)], have been synthesized, characterized, and the crystal structures of the molecules determined. Field-effect transistors fabricated with vapor-deposited and solution-cast films of DFCO-4T exhibit very high Ion:Ioff current ratios (up to 108) and electron mobilities up to approximately 0.51 and approximately 0.25 cm2.V-1.s-1, respectively. Solution-cast blends of P(COFCO-4T) and DFCO-4T (1:1 weight ratio) exhibit an electron mobility of approximately 0.01 cm2.V-1.s-1 (Ion:Ioff = 104). 相似文献
120.
Antonio J Moreno-VargasPierre Vogel 《Tetrahedron letters》2003,44(27):5069-5073
Enantiomerically pure 2,8-diazabicyclo[3.2.1]oct-2-ene derivatives (+)-5 and (−)-5 have been obtained from 2-azido-3-tosyl-7-azabicyclo[2.2.1]heptanes (+)-1 and (−)-2 and their enantiomers, by ring expansion under radical conditions. Compounds (+)-5 and (−)-5 were transformed into hemiaminals 9 ((3S,4R,5R)- and 10 ((3R,4S,5S)-5-(2-aminoethyl)-2,3,4-trihydroxypyrrolidine) that are good inhibitors of α-mannosidases. 相似文献