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At least 1,189 records · Page 66Linked to original sources
PubMed1995

Antihyperglycemic N-sulfonyl-1a,2,6,6a-tetrahydro-1H,4H- [1,3]dioxepino[5,6-b]azirines: synthesis, X-ray structure analysis, conformational behavior, quantitative structure-property relationships, and quantitative structure-activity relationships.

A series of 1-sulfonyl-1a,2,6,6a-tetrahydro-1H,4H- [1,3]dioxepino[5,6-b]azirines, 4, has been synthesized and evaluated for its effects on blood glucose-decreasing activity. These derivatives were prepared from 4,7-dihydro-1,3-dioxepins 1 via vic(acylamino)halogenodioxepanes 2 and dioxepinoazirines 3. Quantitative structure--property relationship and quantitative structure--activity relationship models, based on X-ray and molecular mechanics analyses, to our knowledge the first in the field of antihyperglycemics, were developed. They allow the prediction of properties (RP-HPLC attention times) and activities (hypoglycemic activity ratio) by the Connolly's molecular surface areas. The lead compound in these models, sulfonyldioxepinoazirine 4i, expressed superior antihyperglycemic activity in comparison to metformin in alloxanized mice, irrespective of route of application. It significantly reduced blood glucose levels in glucose-primed mice, but it did not cause a dose dependent decrease of blood glucose level in healthy (nondiabetic, control) animals.

Animals↗
PubMed2001

X-ray crystal structures and conformational analysis of bicyclo[5.3.1]undec-1(11)-enes: twisting versus pyradidalization in anti-bredt olefins.

The synthesis of several 9,11,11-trihalo[5.3.1]propellanes and their 4-dimethylsila analogues is described. They solvolyze under formation of the corresponding isomeric 7,9,11- trihalobicyclo[5.3.l]undec-1(11)-enes which are "anti-Bredt" olefins with a strained trans double bond in a bridged eight-membered ring; in the presence of nucleophiles such as water or ethanol, the corresponding 7-hydroxy or 7-ethoxy derivatives, respectively, are obtained. On the basis of the X-ray crystal structures of four of these compounds (1a, 9a, 15, 17b), the effect of strain and of the substitution pattern on the degree of twisting and pyramidalization of the double bond is discussed.

Journal Article↗
PubMed1997

Synthesis, Conformational Analysis, and Binding Properties of Molecular Clips with Two Different Side Walls.

A new general route toward the synthesis of diphenylglycoluril clips with two different side walls starting from the new precursor 6b and the known compound 2b is described. A variety of clips are accessible in this way, some of them containing metal binding ligand systems, viz. phenanthroline, pyridine, salophen, and porphyrin for future applications as supramolecular catalysts. The physical and binding properties of the new clips are presented and discussed.

Journal Article↗
PubMed2006

Conformational analysis of sulfate species on Ag/Al2O3 by means of theoretical and experimental vibration spectra.

The formation and configuration of sulfate species on Ag/Al2O3 were studied by means of in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and density functional theory (DFT) calculations. The comparison between theoretical and experimental vibration spectra enable us to draw the following conclusions: Bidentate sulfate species rather than tridentate sulfate species are the predominant surface species on Ag/Al2O3. Moreover, both bidentate and tridentate sulfate species may coexist on the catalyst surface at a lower coverage. The accumulation of surface sulfate species could well explain the blue shift of the sulfate species in IR spectra. In addition, the in situ DRIFTS could distinguish between the sulfate species that linked to Al site and Ag site, which was well supported by temperature-programmed desorption (TPD) results.

Journal Article↗
PubMed2006

Conformational analysis. 24. Structure and composition of gaseous oxalyl fluoride, C(2)F(2)O(2): electron-diffraction investigation augmented by data from microwave spectroscopy and molecular orbital calculations.

The molecular structure and composition of gaseous oxalyl fluoride (OXF) has been investigated by electron diffraction (GED) at nozzle-tip temperatures of -10, 149, and 219 degrees C. The GED data were augmented by molecular orbital calculations, and the analysis was aided by use of rotational constants from microwave (MW) spectroscopy. As in the other oxalyl halides, there are two stable species, of which the more stable is periplanar anti (i.e., trans). However, unlike these other halides in which the second form is gauche, the second form of oxalyl fluoride was known from MW work to be periplanar syn (i.e., cis). Our results are consistent with a mixture of trans and cis forms, and yield values for the structural parameters, the composition of the system at the three temperatures cited, and the thermodynamic quantities deltaG(o), deltaH(o), and deltaS(o) for the reaction trans --> cis. Some trans/cis distances (r(g)/Angstrom) and angles (<(alpha)/deg) at -10 degrees C are r(C=O) = 1.178(2)/1.176(2), r(C-F) = 1.323(2)/1.328(2); r(C-C) = 1.533(3)/1.535(3), <(C-C=O) = 126.4(2)/124.2(2), <(C-C-F) = 109.8(2)/112.2(2), and <(O-C-F) = 123.8(2)/123.6(2). The mixture compositions (percent trans) at -10 degrees C/149 degrees C/219 degrees C are 75(3)/58(7)/52(8), from which deltaH(o) and deltaSO) are found to be 1.14 kcal/mol and 2.12 cal/(mol x deg). The system properties are discussed.

Journal Article↗
PubMed2005

Tyrosinase inhibition: conformational analysis based studies on molecular dynamics calculations of bipiperidine based inhibitors.

Two series of variably N-substituted biperidines were synthesized by condensing various acid chlorides, alkyl halides and anhydrides with 1,4-bipiperidine. The new compounds were tested as tyrosinase inhibitors and a structure-activity relationship (SAR) study was carried out. Potent inhibition was observed in the case of the 4'-methylbenzyl substitution on this atom (IC50 = 1.72 microM) with this compound being a lead for future drug design. Additionally, calculations of the important QSAR molecular descriptors were done on the biperidine analogues after their 2 ps molecular dynamics (MD) simulations using molecular mechanics force field (MMFF) approaches. Using MD simulations potential and total energies were calculated for the energy minimized models of bipiperidine and the most active analogs 2, 3, 4, 6, 8 and 10.

Enzyme Inhibitors↗