Griseofulvin (G)

Ohne Zusammenfassung     

Thioreductones and Derivatives (G)

Thioreductones and Derivatives . Replacement of one or two (principally also three) O‐atoms in aci‐reductones by sulfur leads to the corresponding thioreductones. In the present paper, different methods of their synthesis are discussed. Substitution of the bromo nucleofug in the 2‐position of 1,3‐dicarbonyl compounds as well as of a 3‐oxosulfone by selected sulfur nucleophiles is assumed to follow an S_RN1 pathway. Characteristic properties, some typical reactions, and selected derivatives were studied. S‐Alkyl‐ and S‐aryl‐substituted cyclic 2‐thioreductones have been found to be synthons for the preparation of vinylogous reductones (2,3‐diacyl‐1,4‐dihydroxy‐1,3‐dienes) and of tetraacyl ethylenes as their bis‐dehydro products.     

Enantioselective total synthesis of (-)-neovibsanin G and (-)-14-epi-neovibsanin G

The first total synthesis of vibsane-type diterpenoids neovibsanin G and 14-epi-neovibsanin G has been achieved. Key to this endeavour was a late stage EtAlCl(2) mediated skeletal rich cascade leading to the bicyclo[3.3.1]nonane core in one step.     

Inhibition effects of gangliosides G(M1), G(D1a) and G(T1b) on base-catalyzed isomerization of prostaglandin A(2)

Micellar inhibition effect of gangliosides on a degradation of drug was investigated, where ganglioside G(M1) (GM1), G(D1a) (GD1a) and G(T1b) (GTlb) whose sialic acid residue is one, two and three, respectively, were used. The base-catalyzed isomerization of prostaglandin A(2) (PGA(2)) to prostaglandin B(2) (PGB(2)) was chosen as a model experiment. The rate for the isomerization of PGA(2) was determined by measuring the concentration of PGA(2) (and PGB(2)) with a high-performance liquid chromatography. Gangliosides micelles inhibited the isomerization of PGA(2). The inhibition effect of GT1b micelles was larger than that of GD1a micelles. This result would be due to the larger absolute value of surface potential of GT1b micelles, which brings about a larger electrostatic repulsion between micellar surface and OH(-). The terminal sialic acid residue of ganglioside was effective to inhibit the isomerization of PGA(2). GM1 micelles without terminal sialic acid residue but with large aggregation number exhibited a superior steric shielding effect rather than an electrostatically repulsive effect. The inhibition effect of GM1 micelles was enhanced by the mixed micellization with the other ganglioside with a terminal sialic acid residue. GM1-GD1a or GM1-GT1b mixed micelles remarkably inhibited the isomerization of PGA(2). The physiological activity of PGs in the biological membranes containing gangliosides was also discussed.     

High-performance liquid chromatographic assay of N(G)-monomethyl-L-arginine, N(G),N(G)-dimethyl-L-arginine, and N(G),N(G)'-dimethyl-L-arginine using 4-fluoro-7-nitro-2, 1,3-benzoxadiazole as a fluorescent reagent

N(G)-Monomethyl-L-arginine (L-NMMA), N(G),N(G)-dimethyl-L-arginine (ADMA), and N(G),N(G)'-dimethyl-L-arginine (SDMA) are emerging cardiovascular risk factors. A high-performance liquid chromatographic method with fluorescence detection for the simultaneous determination of L-NMMA, ADMA and SDMA is described. The assay employed 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F) as a fluorescent derivatization reagent. After solid phase extraction with cation-exchange column, the methylated arginines were converted to fluorescent derivatives with NBD-F, and the derivatives were separated within 32 min on a reversed-phase column. Nomega-Propyl-L-arginine was Used as an internal standard. Extrapolated detection limits were 12 nM (12 fmol per injection) for L-NMMA and 20 nM (20 fmol per injection) for ADMA and SDMA, respectively, with a signal-to-noise ratio of 3. The calibration curves for L-NMMA, ADMA and SDMA were linear within the range of 50-5000 fmol. The method was applied to the quantitative determination of L-NMMA, ADMA and SDMA in 200 microl of rat plasma. The concentrations of L-NMMA, ADMA and SDMA in rat plasma were 0.16 +/- 0.03, 0.80 +/- 0.25 and 0.40 +/- 0.21 microM, respectively (n = 5).     

Eine indirekte polarographische Methode zur Bestimmung von β-Diäthylamino-äthyl-(o-benzyl-phenyl)äther-hydrochlorid (AH3)

Zusammenfassung Eine indirekte polarographische Methode zur Bestimmung von AH₃ wird beschrieben, das zu diesem Zweck mit rauchender Salpetersäure nitriert wird. Die optimalen Bedingungen für die Nitrierung und Reduktion an der Quecksilbertropfelektrode werden mitgeteilt. Zur Aufstellung einer Eichkurve wird ein scharfes Maximum der Derivativkurven beim Halbstufenpotential –0,60 V benutzt.

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Summary An indirect polarographic method for determining AH₃ is described, that for this purpose is nitrated with fuming nitric acid. The optimal conditions for the nitration and reduction on the mercury dropping electrode are stated. A sharp maximum of the derivative curves at the half-potential –0.60 V was used to set up a calibration curve.

     

The inner-sphere reorganization energies for AH2 + AH (A = Al,Si, P,S) electron self-exchange reactions in electron-transfer processes from ab initio calculations

This article presents an application of the accurate calculation scheme proposed recently for the inner-sphere reorganization energies of molecules of the type AH₂ (A = Al, Si, P, and S). A reasonable extension has been made. The inner-sphere reorganization energies for the title thermal electron self-exchange reactions are calculated in terms of ab initio MO self-consistent field method (HFSCF ) at different basis-set levels (6-31G **, 6-31 + G **, DZ , and DZP ) and the involved parameters are also determined. These calculated results have been calibrated by comparing optimized molecular geometrical parameters and corresponding energy properties with the experimental findings or other theoretical values. An approximation, in which the contribution from the bond length–bond angle to the potential energy surface is neglected, is adopted in constructing the calculation formulas via the function model. Its adequacy is discussed. Agreement among different calculation schemes is analyzed. © 1995 John Wiley & Sons, Inc.     

Symmetry functions adapted to the subgroup chain U(7) ⊃ SO(7) ⊃ G2 ⊃ SO(3) ⊃ G

Summary In this paper the Lie algebra technique is used to construct symmetry functions adapted to the subgroup chain U(7) SO(7) G ₂ SO(3) G, which is one of symmetry group chains appearing in the weak ligand field scheme for f ^N ions. The functions are expressed in terms of the Gelfand states.     

Ab initio studies of chemical equilibria. Equilibria containing first row hydrides AH2, AH3, and AH4 and their positive ions

Equilibrium constants were calculated for fourteen simple reactions involving AH₂, AH₃, and AH₄ first row hydrides and their positive ions. Except for the “experimental” correlation energies used, the theoretical approach is entirely non-empirical in character. The results suggest that if the correlation effects were accounted for in a more sophisticated way, most of the calculated equilibrium constants would be more reliable than the available experimental data.     

几种含芯电子相关能修正的G2和G2(ACI)方法

针对冻结芯电子近似,在MP2/6-311G(d,p)级别上对G2、MP2/6-311G(d)和MP2/6-311G(d,p)级别上对G2(QCI)方法进一步考虑了芯电子相关能修正,尝试建立了G2(fu2)、G2(QCI/ful)和G2(QCI/fu2)方法。G2-l test set 的反应能量计算结果表明,这些方法进一步减小了经验修正量;G2(QCI/ful)和G2(QCI/fu2)也比G2(QCI)的总体精度有所提高;但G2(fu2)在G2基础上,总体精度没有改善。G2(fu2)、G2(QCI/ful)和G2(QCI/fu2)计算G2-l test set反应能量的平均绝对偏差分别为5.11、4.74和4.81kJ mol-1,G2和G2(QCI)分别为5.09和4.97kJ mol-1.     

Total synthesis of (-)-senepodine G and (-)-cermizine C

An efficient, stereospecific synthesis of the alkaloids senepodine G (2) and cermizine C (1) has been completed using the BF3.Et2O-promoted stereospecific addition of Me2CuLi to alpha,beta-unsaturated lactam 6 to provide lactam 3, the addition of MeMgBr followed by HCl to convert 3 to senepodine G (2) (six steps, 40% overall yield), and the stereospecific NaBH4 reduction of 2 to give cermizine C (1) (seven steps, 40% overall yield).     

Vibrational relaxation and νs(AH) absorption band profiles of weak hydrogen-bonded complexes in liquids

The ν _>(AH) IR absorption band profile of a weak hydrogen-bonded complex AH … B embedded in liquid is calculated within the two-mode (ν _>(AH)) and ν_AB coupling scheme. The generalized Langevin equation is invoked to describe the dynamics of the low-frequency (harmonic) ν_AB oscillator influenced by the random force from surrounding molecules. The main goal is to take account of not very short correlation times τ_c of this force, which is likely to be the case in real liquids. The non- zero τ_c value results in an appearance of a purely dissipative mode when A and B approach each other. This is shown to be responsible for the ν _>(AH) bandshaping in the hydrogen-bonded species exhibiting ν _>(AH) band halfwidths smaller than or of the order of the ν_AB vibration frequency. As for the ν_AB absorption band profile, it is formed by the damped oscillatory A→ ← B motional mode. The relationships connecting the characteristics of the ν _>(AH) and ν_AB bandshapes are obtained. It is shown that such entities as the mean-squared A … B length dispersion in solution, the mean-squared fluctuating force acting on the ν_AB oscillator and its correlation time τ_c can be estimated from the joint analysis of the experimental ν _>(AH) and ν_AB band profiles. Comparison with the experimental data for phenol(OD)-pyridine in CCl₄ yields τ_c = (O.6–1.0)x10^?2 s.     

Formal synthesis of (±)-cladoniamide G

The formal synthesis of (±)-cladoniamide G, a natural product that exhibits cytotoxicity against human breast cancer MCF-7 cells, is presented. Our strategy employed a Suzuki–Miyaura coupling to join the two indole subunits of this natural product.     

G3(QCI)模型化学方法

建立了非微扰外推模式下的几种G3(QCI)方法：G3(QCI/fu1)、G3(QCI/fu2)、G3(QCI/ful)//B3PW91和G3(QCI/fu2)//B3PW91.其中,电子能量用QCISD(T,FC)/G3large直接计算,芯电子相关能分别在MP2/6-31G(d)和MP2/6-31G(d,p)级别上计算,对125个G2-1 test set 的计算结果表明,总体精度与G3和G3 //B3LYP相当;平均绝对偏差分别为4.370、4.389、4.061和4.022kJ mol-1,相应G3和G3//B3LYP分别为4.27和4.05kJ mol-1.文章提出的方法排除了G3中外推办法的不确定因素,且更适用于非平衡几何构型体系能量的定量计算。