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91.
Tanja Soldatović Predrag Čanović Radivoje Nikolić Ratomir Jelić Živadin D. Bugarčić 《Journal of solution chemistry》2009,38(1):57-71
The formation equilibria of the [Pt(SMC)(H2O)2]+ complex with some biologically relevant ligands such as L-methionine (L-met) and glutathione (GSH) were studied. The stoichiometry
and stability constants of the formed complexes are reported, and the concentration distribution of the various complex species
has been evaluated as a function of pH. The reaction between [PtCl2(SMC)] and guanosine-5′-monophosphate (5′-GMP) was studied by 1H NMR spectroscopy. The NMR spectra indicated that first step is the hydrolysis of the [PtCl2(SMC)] complex and second step is the substitution of an aqua ligand, either in the cis or trans position with guanosine-5′-monophosphate in molar ratio 1:1. The values of rate constant showed faster substitution of coordinated
H2O in the trans position to the S donor atom of S-methyl-L-cysteine, whereas the slower reaction was assigned to the displacement of the
cis coordinated aqua molecule. This is due to the strong trans labilization effect of coordinated sulfur.
Electronic Supplementary Material The online version of this article () contains supplementary material, which is available to authorized users. 相似文献
92.
Tanja Grkovic 《Tetrahedron》2009,65(32):6335-207
A survey of the secondary metabolite chemistry profiles of New Zealand sponges of the genus Latrunculia has yielded new members of the discorhabdin A- and B-type families. The structure elucidation of (+)-(6R,8S)-1-thiomethyldiscorhabdin G∗/I (5) and both enantiomers of 16a,17a-dehydrodiscorhabdin W (6) are reported. Absolute configurations were assigned by comparison with a dataset of recently reported electronic circular dichroism spectra of discorhabdin alkaloids. A stereochemical correction of the recently reported natural product (+)-3-dihydrodiscorhabdin A from (3S,5R,6S,8S)-(7) to the C3-epimeric (+)-(3R,5R,6S,8S)-(8) and assignment of absolute configuration is also presented. Semi-synthesis of (+)-(3S,5R,6S,8S)-(7) from (+)-discorhabdin A provided further evidence for this structure revision. Cytotoxicity data is reported for 5-8. 相似文献
93.
Bringmann G Kajahn I Reichert M Pedersen SE Faber JH Gulder T Brun R Christensen SB Ponte-Sucre A Moll H Heubl G Mudogo V 《The Journal of organic chemistry》2006,71(25):9348-9356
The isolation and structural elucidation of three novel-type naphthylisoquinoline alkaloids, ancistrocladinium A and B (the latter along with its atropisomer), from a Congolese Ancistrocladus species collected in the habitat Yeteto is reported. Their structures, including all stereochemical features, were elucidated by spectroscopic, chemical, and chiroptical methods. Ancistrocladinium A and B are the first N,C-coupled naphthyldihydroisoquinoline alkaloids found in nature, i.e., with an iminium-aryl axis. Although ancistrocladinium A, which is N,8'-coupled, is configurationally stable at this axis, ancistrocladinum B and its rotational isomer are based on a hitherto unprecedented N,6'-coupling type, with a slow rotation about the hetero biaryl axis at room temperature; they thus occur as a 46:54 mixture of two configurationally semistable atropo-diastereomers. For the isomerization of (P)-ancistrocladinium B to its (M)-diastereomer and for the opposite direction, the Gibbs free energies of activation were determined to be DeltaG double dagger1 = 105.8 kJ mol-1 and DeltaG double dagger2 = 105.7 kJ mol-1, respectively. In addition, the compounds were shown to have promising antileishmanial activities. 相似文献
94.
Dr. Yuzhou Wu Prof. Dr. Fedor Jelezko Prof. Dr. Martin B Plenio Prof. Dr. Tanja Weil 《Angewandte Chemie (International ed. in English)》2016,55(23):6586-6598
The currently available techniques for molecular imaging capable of reaching atomic resolution are limited to low temperatures, vacuum conditions, or large amounts of sample. Quantum sensors based on the spin‐dependent photoluminescence of nitrogen‐vacancy (NV) centers in diamond offer great potential to achieve single‐molecule detection with atomic resolution under ambient conditions. Diamond nanoparticles could also be prepared with implanted NV centers, thereby generating unique nanosensors that are able to traffic into living biological systems. Therefore, this technique might provide unprecedented access and insight into the structure and function of individual biomolecules under physiological conditions as well as observation of biological processes down to the quantum level with atomic resolution. The theory of diamond quantum sensors and the current developments from their preparation to sensing techniques have been critically discussed in this Minireview. 相似文献
95.
A stereospecific photochemical ring contraction was used as the key step in the first total synthesis of the marine pseudopteranyl diterpene 11-gorgiacerol and its 11-epimer. The synthesis allowed the correction of the configurations that had been misassigned in the literature. In addition, some novel pseudopteranyl derivatives have been made. 相似文献
96.
Chia PW Livesey MR Slawin AM van Mourik T Wyllie DJ O'Hagan D 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(28):8813-8819
N-Methyl-D-aspartate (NMDA) is the prototypical agonist of the NMDA receptor subtype of ionotropic glutamate receptors. Stereogenic placement of a C-F bond at the 3-position of (S)-NMDA generates either the (2S,3S)- or (2S,3R)- diastereoisomers of 3F-NMDA. The individual diastereoisomers were prepared by synthesis in enantiomerically pure forms and it was found that (2S,3S)-3F-NMDA is an agonist with a comparable potency to NMDA itself, whereas the (2S,3R)-diastereoisomer has negligible potency. The difference in potency of these stereoisomers is attributed to a preference of the C-F bond (2S,3S)-3F-NMDA to adopt a gauche conformation to the C-N(+) bond in the binding conformation, whereas the (2S,3R)-3F-NMDA forces these bonds anti, losing electrostatic stabilisation, to achieve the required binding conformation. These observations illustrate the utility of stereoselective fluorination in influencing the molecular conformation of β-fluorinated amino acids and thus probing the active conformations of bioactive compounds at receptors. 相似文献
97.
Schulz-Gasch T Schärfer C Guba W Rarey M 《Journal of chemical information and modeling》2012,52(6):1499-1512
Advantages like intuitive interpretation, objectivity, general applicability, and its easy, automated calculation make the rmsd (root-mean-squared deviation) the measure of choice for the investigation of the accuracy of conformational model generators. For comparing conformations of a single molecule this is a clearly superior method. Single molecule analysis is, however, a rare scenario. Typically, conformations are generated for huge corporate or external vendor databases of high diversity which are then further investigated with high-throughput computational methods like docking or pharmacophore searching, in virtual screening campaigns. Representative subsets for accuracy investigations of computational methods need to mimic this diversity. Averaged rmsd values over these data sets are frequently used to assess the accuracy of the methods. There are, however, significant weaknesses in rmsd comparisons for such kind of data sets. The interpretation is for example no longer intuitive because what can be expected in terms of good or bad rmsd values crucially depends on the data set composition like size or number of rotatable bonds of the underlying molecules. Further, rmsd lacks normalization which might result in very high averaged rmsd values for highly flexible molecules and thus might completely skew results. We have developed a novel measure to compare conformations of molecules called Torsion Fingerprint Deviation (TFD). It extracts, weights, and compares Torsion Fingerprints from a query molecule and generated conformations under consideration of acyclic bonds as well as ring systems. TFD is alignment-free and overcomes major limitations of rmsd while retaining its advantages. 相似文献
98.
99.
A Kaiser S Spies T Lommel C Richert 《Angewandte Chemie (International ed. in English)》2012,51(33):8299-8303
Extending both ways: A method for DNA-templated synthesis on solid support is described. Controlled, stepwise chain extension was demonstrated both in the direction favored by nature (3'-extension; see scheme) and in the direction typical for conventional DNA synthesizers (5'-extension). 相似文献
100.
Espinosa-Marzal RM Drobek T Balmer T Heuberger MP 《Physical chemistry chemical physics : PCCP》2012,14(17):6085-6093
In this work we revisit the surface forces measured between two atomically flat mica surfaces submerged in a reservoir of potassium nitrate (KNO(3)) solution. We consider a comprehensive range of concentrations from 0.08 mM to 2.6 M. The significantly improved resolution available from the extended surface force apparatus (eSFA) allows the distinction of hydration structures and hydrated-ion correlations. Above concentrations of 0.3 mM, hydrated-ion correlations give rise to multiple collective transitions (4 ± 1 ?) in the electrical double layers upon interpenetration. These features are interpreted as the result of hydrated-ion ordering (e.g. layering), in contrast to the traditional interpretation invoking water layering. The hydrated-ion layer adjacent to the surface (i.e. outer Helmholtz layer) is particularly well defined and plays a distinctive role. It can be either collectively expelled in a 5.8 ± 0.3 ? film-thickness transition or collectively forced to associate with the surface by external mechanical work. The latter is observed as a characteristic 2.9 ± 0.3 ? film-thickness transition along with an abrupt decrease of surface adhesion at concentrations above 1 mM. At concentrations as low as 20 mM, attractive surface forces are measured in deviation to the DLVO theory. The hydration number in the confined electrolyte seems to be significantly below that of the bulk. A 1-3 nm thick ionic layer solidifies at the surfaces at concentrations >100 mM, i.e. below bulk saturation. 相似文献