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91.
92.
Giovanna Gasparri Fava Marisa Belicchi Ferrari Giovanni Casiraghi Gloria Rassu Pietro Spanu 《Journal of chemical crystallography》1991,21(5):629-633
The crystal structure of the title lactone, C20H30O9, a potential precursor of uncommon 11-carbon sugar derivatives, has been determined by single-crystal diffraction methods. The compound crystallizes in the orthorhombic space groupP212121 witha=15.581(3),b=14.047(2),c=9.888(2) Å, andZ=4. The structure was solved by direct methods and refined by full-matrix least-squares toR=0.054. The absolute configuration of the seven stereogenic carbon atoms was deduced as 4R, 5R, 6R, 7R, 8S, 9R, 10R, being (R)-(+)-glyceraldehyde its progenitor. An intramolecular O-HO hydrogen bond is present. Weak interaction C-HO links the molecules in sheets parallel to the (100) plane. 相似文献
93.
Giovanna Gasparri Fava Marisa Ferrari Belicchi Daniele Belletti Giovanni Casiraghi Gloria Rassu 《Journal of chemical crystallography》1991,21(3):261-264
The crystal structure of the title lactone, C13H18O7, has been determined by single crystal diffraction methods. The compound crystallizes in the monoclinic space groupP21 witha=13.231(2),b=10.248(2),c=5.348(1) Å,=96.66(2)°, andZ=2. A total of 1055 reflection intensities were recorded on a Siemens AED single-crystal diffractometer (CuK radiation) at room temperature. The structure was solved by direct methods and electron density calculations. Full-matrix least-squares refinement gaveR=0.055 for 946 unique reflections above 2(I). The absolute configuration of the six chiral carbon atoms was deduced as 4S, 5R, 6R, 7S, 9R, 10R (crystallographic numbering corresponds to C-6, 5, 4, 3, 2, 1 in the title compound). An intermolecular O-HO hydrogen bond joins the molecules in chains which run along the twofold screw axis. 相似文献
94.
95.
Alipázaga MV Moreno RG Linares E Medeiros MH Coichev N 《Dalton transactions (Cambridge, England : 2003)》2005,(23):3738-3744
NiIIGGH (GGH = glycylglycylhistidine) reacts rapidly with S(IV), in air-saturated solution, to produce NiIIIGGH. A mechanism is proposed where initial NiIII oxidizes SO3(2-) to SO3*-, which reacts with dissolved oxygen to produce SO5*-, initiating radical chain reactions. DNA strand breaks and 8-oxo-7,8-dihydro-2'-deoxyguanosine formation were observed in air-saturated solutions containing micromolar concentrations of Ni(II) and S(IV). The extent of DNA damage showed dependence on the ratio of the NiIIGGH : S(IV) concentrations and the ionic strength. 相似文献
96.
97.
A computational method to determine the energetically favorable positions of functional groups with respect to the transition states of stereoselective reactions based on force field energy minimization is presented. The parameters of this functionality mapping, the characteristics of the target transition states, and the features of the probe structures are outlined. Our method was found to reproduce the positions of the stereodiscriminating fragments for some known chiral ligands including the Masamune dimethylborolane, dimenthylborane, the Corey stien reagent, the Roush allylboronate tartrates, and the secondary amine Diels-Alder catalysts described by MacMillan. Functionality mapping can be used to better understand the specific interactions in the transition states leading to the products by providing a quantitative measure of the stabilization/destabilization afforded by the different ligand components via nonbonded interactions. The method can determine if a chiral ligand imparts the observed selectivity by stabilizing one reaction pathway, by destabilizing a reaction pathway, or by a combination of both. Orientational as well as positional information about potential functional groups is readily obtained. In addition to its utility as an analytical tool, functionality mapping can be used to explore starting points for the design of new chiral ligands. 相似文献
98.
Gerhard Buchbauer Gabriele Püspök Adelheid Angermayer Elisabeth Silbernagel Marisa Manz 《Monatshefte für Chemie / Chemical Monthly》1987,118(3):387-398
The synthesis of 4-(3,3-dimethyl-2-exo-norbornyl)-2-methyl-2-buten-1-ol (5), an analogue of -santalol (1) has been described. One route to5 starts with isocamphenilanyl propionic acid (8) which can be prepared in 4 steps from isocamphenilanic acid (9). Also 4 steps lead from8 to the target molecule5 with an overall yield of 24%. By a second and more convergent route, starting from the very easily obtainable bicyclic ketone19, the allylic alcohol5 could be obtained again in 4 steps, but this time with an overall yield of 1.3%. A new and easy synthesis of isocamphenilanyl acetic acid (15), a potential starting material to5, has been described, also the preparation of some new isocamphane derivatives.
26. Mitt:Buchbauer G,Pernold W,Ittner M,Ahmadi MF,Dobner R,Reidinger R (1985) Monatsh Chem 116: 1209 相似文献
99.
Kozlowski MC Dixon SL Panda M Lauri G 《Journal of the American Chemical Society》2003,125(22):6614-6615
Quantitative structure selectivity relationship (QSSR) models are described that provide consistently reliable predictions for the asymmetric addition of Et2Zn to PhCHO catalyzed by beta-amino alcohols. Statistically valid two-variable linear regression models that correlate the structures of the chiral catalysts with their enantioselectivities are obtained from three-dimensional physical property grids. The strength of the present method is that statistical models obtained from a small set of experimentally determined selectivities and relatively simple theoretical calculations yield selectivity predictions that are as accurate as those derived from higher-level calculations of transition-structure energies. Only minutes of computing time are required. Simple models are obtained which permit straightforward physical interpretation and generate realistic predictions. 相似文献
100.
Marisa Belicchi-Ferrari Franco BisceglieChiara Cavalieri Giorgio PelosiPieralberto Tarasconi 《Polyhedron》2007
This paper reports the synthesis and characterization of six compounds of copper(I), stabilized in its reduced state by two triphenylphosphines, in which 4-fluorobenzaldehyde thiosemicarbazone and N-methylthiosemicarbazone act as chelating through their sulfur and imino nitrogen. The three oxoanions that have been chosen, NO3−, SO42− and CH3COO−, play an important role: their oxygens are bad competitors with the imino nitrogen of the thiosemicarbazone moiety and moreover they form strong charge assisted hydrogen bondings that stabilize the neutral form of the ligand. The overall packing is determined by intermolecular phenyl–phenyl van der Waals interactions. 相似文献