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Hans‐Dietrich Stachel Barbara Zimmer Eduard Eckl Katharina Semmlinger Wolfgang Weigand Ralf Wünsch Peter Mayer 《Helvetica chimica acta》2005,88(6):1208-1220
The 1,2‐dithiolosultam derivative 14 was obtained from the (α‐bromoalkylidene)propenesultam derivative 9 (Scheme 1). Regioselective cleavage of the two ester groups (→ 1b or 2b ) allowed the preparation of derivatives with different substituents at C(3) in the dithiole ring (see 27 and 28 ) as well as at C(6) in the isothiazole ring (see 17 – 21 ; Scheme 2). Curtius rearrangement of the 6‐carbonyl azide 21 in Ac2O afforded the 6‐acetamide 22 , and saponification and decarboxylation of the latter yielded ‘sulfothiolutin’ ( 30 ). Hydride reductions of two of the bicyclic sultams resulted in ring opening of the sultam ring and loss of the sulfonyl group. Thus the reduction of the dithiolosultam derivative 14 yielded the alkylidenethiotetronic acid derivative 33 (tetronic acid=furan‐2,4(3H,4H)‐dione), and the lactam‐sultam derivative 10 gave the alkylidenetetramic acid derivative 35 (tetramic acid=1,5‐dihydro‐4‐hydroxy‐2H‐pyrrol‐2‐one) (Scheme 3). Some of the new compounds ( 14, 22, 26 , and 30 ) exhibited antimycobacterial activity. The oxidative addition of 1 equiv. of [Pt(η2‐C2H4)L2] ( 36a , L=PPh3; 36b , L=1/2 dppf; 36c , L=1/2 (R,R)‐diop) into the S? S bond of 14 led to the cis‐(dithiolato)platinum(II) complexes 37a – c . (dppf=1,1′‐bis(diphenylphosphino)ferrocene; (R,R)‐diop={[(4R,5R)‐2,2‐demithyl‐1,3‐dioxolane‐4,5‐diyl]bis(methylene)}bis[diphenylphosphine]). 相似文献
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B. A. Bushaw H. -J. Kluge J. Lantzsch R. Schwalbach J. Stenner H. Stevens K. Wendt K. Zimmer 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1993,28(4):275-281
The hyperfine spectra of the 5s4d 3 D 1-5s20f, 5s4d 3 D 2-5s23f, and 5s 4d 3 D 3-5s32f transitions of87Sr (I=9/2) have been measured by collinear fast beam laser spectroscopy. The structure in the upper configurations is highly perturbed by fine structure splitting that is of comparable size to the hyperfine interaction energy. These perturbations can be adequately treated with conventional matrix diagonalization methods, using the 5s-electron magnetic dipole interaction terma 5s and the unperturbed fine structure splittings as input parameters. Additionally, hyperfine constants for the lower 5s4d 3 D configurations, including theA- andB-factors and a separation of the individuals- andd-electron contributions to these factors, are derived. 相似文献
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Database analysis and molecular mechanics were used to determine the conformational flexibility of tridentate scorpionate ligands. The tris(pyrazolyl)methane and tris(pyrazolyl)borate ligands act like molecular vises, opening their tripodal structure for larger metals and closing around smaller metal ions. Tris(3-tert-butylpyrazolyl)methane has significant preference for larger metal ions than its unsubstituted parent compound. Tris(pyrazolyl)methanes and tris(pyrazolyl)borates have similar conformational flexibilities. Placing sterically hindered groups on the central carbon or boron has only a minor effect on the geometry of the tris(pyrazolyl)methanes and tris(pyrazolyl)borates. However, it does influence the flexibility of the ligands, particularly when they have to open far from their ideal geometry, which commonly occurs. 相似文献
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Magnetic Circular Dichroism Study of Analogues of the DNA Binding Ligands Netropsin and Distamycin A
UV absorption and MCD data of a complete series of netropsin-like oligopeptides containing between one and five N-methyl-pyrrole residues are reported. The presence of three MCD bands in the region between 220 and 350 nm can be related to the resonance of the peptide groups with the methylpyrrole systems of the oligopeptides. The longest wavelength absorption bands of all netropsin-like compounds investigated are ascribed to two electronic transitions of the resonance methypyrrole-carboxamide units. - Complex formation with DNA affects these MCD bands and hence modifies the transitions. This is explained by hypercon-jugation in the chromophoric system as a result of specific hydrogen bonding of peptide groups with dA·dT pairs of double stranded DNA. 相似文献
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The chemical versatility of 2,4(3H,5H)-furandione (β-tetronic acid, 1) and its synthetic applicability are of considerable current interest1b,2a-k. The multifunctional character of this small molecule confers an intriguing synthetic potential which has prompted us to develop synthetic schemes utilizing it as a synthon for certain heterocyclic systems. 相似文献