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131.
Francesco Trotta Giovanni Moraglio Orfeo Zerbinati Antonello Nonnato 《Journal of inclusion phenomena and macrocyclic chemistry》1995,23(4):269-276
The synthesis is described of alkyl capped carbonates of-cyclodextrin, obtained from diols activated with carbonyldiimidazole. The reaction preferentially gave monocapped derivatives which were characterized by HPLC, TLC, FT-IR and13C-NMR. These compounds are stable at pH <7, and methyl orange was found to form stronger inclusion compounds with capped-cyclodextrin than with the parent-cyclodextrin. Paramagnetic Gd(III) complexes were also studied, but they were found to be included into capped-cyclodextrin as well as into-cyclodextrin.Part of this work was presented at the 7th International Symposium on Cyclodextrins, 1994, Tokyo, April 25–28, Book of Abstract, page 54. 相似文献
132.
Benedetto Di Blasio Antonello Santini Vincenzo Pavone Carlo Pedone Ettore Benedetti Vittorio Moretto Marco Crisma Claudio Toniolo 《Structural chemistry》1991,2(5):523-527
A synthetic, terminally blocked homohexapeptide from-aminoisobutyric acid has been examined by single-crystal X-ray diffraction and the structure refined toR = 0.047. The compound is folded into almost two turns of a 310-helix, stabilized by four consecutive intramolecular N—H·O=C H-bonds. An asymmetric covalent geometry for the-aminoisobutyric acid residues, known to be responsible for the onset of the 310-helix in homopeptides from this C,-dialkylated-aminoacid on the basis of a theoretrical conformational analysis, has been experimentally found also in this structure. 相似文献
133.
Filippi A Trout NA Brunelle P Adcock W Sorensen TS Speranza M 《The Journal of organic chemistry》2004,69(17):5537-5546
The diastereofacial selectivity of 2-methyl-5-X-adamant-2-yl cations IX (X = CN, Cl, Br, CH3O, COOCH3, C6H5, CH3, and (CH3)3Sn) toward methanol has been investigated in the gas phase at 750 Torr and in the 40-120 degrees C temperature range and compared with that of IF (X = F) and ISi (X = (CH3)3Si) measured previously under similar conditions. Detailed analysis of the energy surface of the IMe (X = CH3) ion reveals that the activation barrier of its syn addition to methanol is significantly lower than that of the anti attack. In the 40-100 degrees C range, such a difference is strongly reduced by adverse entropic factors which are large enough to invert the IMe diastereoselectivity from syn to anti at T > 69 degrees C. The behavior of IMe diverges markedly from that of IF and ISi. Large adverse entropic factors account for the predominant syn diastereoselectivity observed in the reaction with IF (X = F), notwithstanding the anti enthalpy barrier is lower than the syn one. Adverse entropy plays a minor role in the reaction with ISi (X = (CH3)3Si) which instead exhibits a preferred anti diastereoselectivity governed by the activation enthalpies. Depending on the electronic properties of X, the kinetic behavior of the other IX ions obeys one of the above models. The gas-phase diastereoselectivity of IX ions responds to a subtle interplay between the sigma-hyperconjugative/electrostatic effects of the X substituent and the activation entropy terms. sigma-Hyperconjugation/field effects determine the pyramidal structure and the relative stability of the syn and anti conformers of IX as well as the relative stability of their addition transition structures and their position along the reaction coordinate. The diastereoselectivity of IX in the gas phase is compared with that measured in solution and with theoretical predictions. 相似文献
134.
R. Acciarri M. Antonello B. Baibussinov M. Baldo-Ceolin P. Benetti F. Calaprice E. Calligarich M. Cambiaghi N. Canci F. Carbonara F. Cavanna S. Centro A.G. Cocco F. Di Pompeo G. Fiorillo C. Galbiati V. Gallo L. Grandi G. Meng I. Modena C. Vignoli 《Nuclear Physics B - Proceedings Supplements》2009,173(1):70-73
135.
Razvigor Ossikovski Makrina Anastasiadou Antonello De Martino 《Optics Communications》2008,281(9):2406-2410
We show that the product decomposition of a depolarizing Mueller matrix (S.-Y. Lu, R.A. Chipman, J. Opt. Soc. Am. A 13 (1996) 1106) as well as the recently proposed reverse decomposition (R. Ossikovski, A. De Martino, Opt. Lett. 32 (2007) 689) need to be extended in order to account for Mueller matrices with negative determinants. The necessity of such an extension of the formalism is illustrated on experimentally determined Mueller matrices. The procedure of the modified decomposition formalism is explicitly described. 相似文献
136.
137.
138.
Fago G Filippi A Giardini A Laganà A Paladini A Speranza M 《Angewandte Chemie (International ed. in English)》2001,40(21):4051-4054
139.
Haak RM Decortes A Escudero-Adán EC Martínez Belmonte M Martin E Benet-Buchholz J Kleij AW 《Inorganic chemistry》2011,50(17):7934-7936
We describe a selective and template-controlled synthesis of a series of Zn(8) metal complexes based on a bis-nucleating salen ligand scaffold. Our results, a combination of X-ray analysis and solution studies, show that discrete, shape-persistent metal clusters can be prepared in high yield. Their activity in organic carbonate catalysis is a function of the metal-connecting fragment present in the exterior of the cluster complex. The high stability of the clusters has been confirmed by (1)H, (13)C (DEPTQ) and DOSY NMR, gel permeation chromatography, high-performance liquid chromatography, and mass spectrometry. 相似文献
140.
Vitagliano L Vergara A Bonomi G Merlino A Verde C di Prisco G Howes BD Smulevich G Mazzarella L 《Journal of the American Chemical Society》2008,130(32):10527-10535