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241.
242.
The metal-binding site of a Helicobacter pylori ATPase 439 (heli(WT)-tag) was successfully used as a new fusion peptide for immobilized metal ion affinity chromatography (IMAC). It produced higher yields than the frequently used his6-tag. Due to stronger binding of the peptide to metal ions, harsher elution conditions were, however, necessary. This undesired side-effect was overcome by modifying the heli(WT)-tag by polymerase chain reaction-directed mutagenesis. The modified tags were screened by an automated high-throughput IMAC system, leading to a heliM14-tag peptide that could be eluted under conditions similar to those of the his6-tag but at the same time produced 20% higher yields of the desired protein. 相似文献
243.
Hans Jürgen Rosenkranz Barbara Winkler-Lardelli Hans-Jürgen Hansen Hans Schmid 《Helvetica chimica acta》1974,57(3):887-916
It is shown that treatment of indolines like 4a-methyl-1,2,3,4,4a,9a-hexahydrocarbazole ( 1 ) and even indoline-alkaloids like 5 or 6 (cf. scheme 1) with KMnO4 in boiling acetone solution leads to the indolenines 10, 29 and 33 , respectively, and, in relatively high yields, to N,N′- or C,N-coupling products (cf. schemes 2 and 5). The results of the oxidation of 6- or 8-methoxy-indolines are shown in schemes 3 and 4, respectively. Analogous ‘dimeric’ dehydrogenation products are observed when tetrahydroquinolines ( 8 and 9 , resp.) are treated with KMnO4 (cf. schemes 7 and 8, resp.). The formation of the bis-compounds is almost certainly due to the coupling of two intermediate indolenyl or tetrahydroquinolyl radicals. The cleavage of the hydrazine derivatives 11 or 17 (scheme 9) also leads to ‘dimeric’ C,N-coupling products. By heating the hydrazine derivative 17 with aqueous HCl, a complete cleavage into indoline 2 and the indolenines 16 and 20 is observed. The reaction is rationalized in scheme 10. So far no naturally occurring alkaloids related to the above mentioned C,N-coupling products have been found. 相似文献
244.
Leibold C Foropoulos J Marsden HM Shreeve JM Oberhammer H 《Inorganic chemistry》2002,41(23):6125-6128
A gas-phase electron diffraction study of the azoxy compound which was synthesized by the reaction of CF3NO with N2F4 in a Pyrex glass vessel results in a trans CF3N(O)NF structure (F trans to CF3), although quantum chemical calculations (MP2 and B3LYP) predict a greater stability of the cis CF3NN(O)F isomer by about 12 kcal/mol. The CF3 group eclipses the N=N double bond. The following skeletal geometric parameters (r(a) values with 3sigma uncertainties) were obtained: N=N 1.287(15) A; N=O 1.231(6) A; N-F 1.380(6) A; N-C 1.498(6) A; N=N=O 131.2(13) degrees; N=N-F 103.5(13) degrees; N=N-C 114.0(12) degrees. The bond lengths in CF3N(O)NF are compared to those in azo, nitryl, and nitrosyl compounds with fluorine and/or CF3 substituents. 相似文献
245.
K. Jurkschat B. Schmid M. Dybiona U. Baumeister H. Hartung A. Tzschach 《无机化学与普通化学杂志》1988,560(1):110-118
Structure and Reactivity of Stannylated Propyl Amines and Propyl Sulfides. Crystal and Molecular Structure of Bis(3-chlorodimethylstannylpropyl)sulfide S(CH2CH2CH2SnMe2Cl)2 The synthesis and reactivity of stannylated propyl amines and propyl sulfides, respectively, E(CH2CH2CH2SnMe3)2 ( 1 , E ? NMe; 2 E ? S) and N(CH2CH2CH2SnMe3)3 3 are reported. 1 and 3 react with dimethyl dichlorostannane under thermal cyclisation to 1,5-dimethyl-5-chloro-1aza-5-stannabicyclo[3.3.01,5]octane Me(Cl)Sn(CH2CH2CH2)2NMe 4 and 5-chloro-1-aza-5-stannatricyclo[3.3.3.01,5]-undecane ClSn(CH2CH2CH2)3N 5 , respectively. The reaction of 2 with dimethyl dichlorostannane leads to the formation of bis(3-chloro-dimethylstannylpropyl)sulfide S(CH2CH2CH2SnMe2Cl)2 6 , whereas the treatment of 2 with tin tetrachloride yields the bis(3-di-chloro-methylstannylpropyl)sulfide S(CH2CH2CH2SnMeCl2)2 7 . The 1H, 13C, and 119Sn NMR data are discussed. 6 crystallizes in the ortho-rhombic space group Pna21 with the unit cell parameters a = 2275.0(1), b = 733.6(2), c = 1062.0(4) pm, V = 1.77273 nm3, Z = 4. The structure was refined to a final R value of 0.041. Both tin atoms adopt distorted trigonal bipyramidal configurations as a result of intramolecular interactions with the bridging sulphur. The sulphur and the chlorine atoms occupy the apical positions. The Sn? S distances amount to 309.7(4) and 311.8(4) pm. 相似文献
246.
Leibold C Alvarez RM Cutin EH Della Vedova CO Oberhammer H 《Inorganic chemistry》2003,42(13):4071-4075
The IR (gas) and Raman (liquid) spectra of FC(O)NSCl(2) demonstrate the presence of a conformational mixture in both phases. According to a gas electron diffraction study, the main conformer (94(8)%) possesses a syn-syn structure (C(O)F group synperiplanar with respect to the SCl(2) bisector and the C=O bond synperiplanar to the N=S bond). Quantum chemical calculations (HF, B3LYP and MP2 with 6-31G basis set, and MP2/6-311(2df)) predict a syn-anti structure for the second conformer. Analysis of the IR (gas) spectrum results in a contribution of 5(1)% of the minor form, corresponding to a Gibbs free energy difference DeltaG degrees = G degrees (syn-anti) - G degrees (syn-syn) = 1.75(15) kcal/mol. This value is reproduced very well by quantum chemical calculations, which include electron correlation effects (DeltaG degrees = 1.28-1.56 kcal/mol). The HF approximation overestimates this energy difference (DeltaG degrees = 3.24 kcal/mol). 相似文献
247.
Reisner E Arion VB Rufińska A Chiorescu I Schmid WF Keppler BK 《Dalton transactions (Cambridge, England : 2003)》2005,(14):2355-2364
Reaction of the antitumor complex trans-[Ru(III)Cl4(Hind)2]- (Hind = indazole) with an excess of dimethyl sulfoxide (dmso) in acetone afforded the complex trans,trans,trans-[Ru(II)Cl2(dmso)2(Hind)2] (1). Two other isomeric compounds trans,cis,cis-[Ru(II)Cl2(dmso)2(Hind)2] (2) and cis,cis,cis-[Ru(II)Cl2(dmso)2(Hind)2] (3) have been obtained on refluxing cis-[Ru(II)Cl(2)(dmso)(4)] with 2 equiv. of indazole in ethanol and methanol, respectively. Isomers 1 and 2 react with acetonitrile yielding the complexes trans-[Ru(II)Cl2(dmso)(Hind){HN=C(Me)ind}].CH3CN (4.CH3CN) and trans,cis-[Ru(II)Cl2(dmso)2{HN=C(Me)ind}].H2O (5.H2O), respectively, containing a cyclic amidine ligand resulting from insertion of the acetonitrile C triple bond N group in the N1-H bond of the N2-coordinated indazole ligand in the nomenclature used for 1H-indazole. These are the first examples of the metal-assisted iminoacylation of indazole. The products isolated have been characterized by elemental analysis, IR spectroscopy, UV-vis spectroscopy, electrospray mass-spectrometry, thermogravimetry, differential scanning calorimetry, 1H NMR spectroscopy, and solid-state 13C CP MAS NMR spectroscopy. The isomeric structures of 1-3 and the presence of a chelating amidine ligand in 4 and 5 have been confirmed by X-ray crystallography. The electrochemical behavior of 1-5 and the formation of 5 have been studied by cyclic voltammetry. 相似文献
248.
A New Aminoazirine Reaction. Formation of 3,6-Dihydropyrazin-2(1H)-ones The reaction of 3-(dimethylamino)-2H-azirines 1 and 2-(trifluoromethyl)-1,3-oxazol-5(2H)-ones 5 in MeCN or THF at 50–80° leads to 5-(dimethylamino)-3,6-dihydropyrazin-2(1H)-ones 6 (Scheme 3). Reaction mechanisms for the formation of 6 are discussed: either the oxazolones 5 react as CH-acidic heterocycles with 1 (Scheme 4), or the azirines 1 undergo a nucleophilic attack onto the carbonyl group of 5 (Scheme 6). The reaction via intermediate formation of N-(trifluoroacetyl)dipeptide amide 8 (Scheme 5) is excluded. 相似文献
249.
Photochemie von tricyclischen β, γ-γ′, δ′-ungesättigten Ketonen. 50. Mitteilung über Photoreaktionen
Photochemistry of tricyclic β, γ-γ′, δ′-unsaturated ketones The easily available tricyclic ketone 1 (cf. Scheme 1) with a homotwistane skeleton yielded upon direct irradiation the cyclobutanone derivative 3 by a 1,3-acyl shift. Further irradiation converted 3 into the tricyclic hydrocarbon 4 . However, acetone sensitized irradiation of 1 gave the tetracyclic ketone 5 by an oxa-di-π-methane rearrangement. Again with acetone as a sensitizer the ketone 5 was quantitatively converted to the pentacyclic ketone 6 . The conversion 5 → 6 represents a novel photochemical 1,4-acyl shift. The possible mechanisms are discussed (see Scheme 7). The tricyclic ketone 2 underwent similar types of photoreactions as 1 (Scheme 2). Unlike 5 the tetracyclic ketone 9 did not undergo a photochemical 1,4-acyl shift. The epoxides 10 and 14 derived from the ketones 1 and 2 , respectively, underwent a 1,3-acyl shift upon irradiation followed by decarbonylation, and the oxa-di-π-methane rearrangement (Schemes 3 and 4). The diketone 18 derived from 1 behaved in the same way (Scheme 5). The tetracyclic diketone 21 cyclized very easily to the internal aldol product 22 under the influence of traces of base (Scheme 5). Upon irradiation the γ, δ-unsaturated ketone 24 underwent only the Norrish type I cleavage to yield the aldehyde 25 (Scheme 6). 相似文献
250.
Ulrike Gabriella Wagner Christoph Kratky Heinz Falk Heinz Flödl 《Monatshefte für Chemie / Chemical Monthly》1987,118(10):1185-1194
The crystal structure of the pentapyrrin1 was determined by X-ray diffraction methodes at two temperatures (298K and 97K). It is the first structure determination of a linear polypyrrole with more than four pyrrole rings. In the crystal, the molecule is located on a crystallographic two-fold axis, which passes through the central pyrrole ring. It assumes a helical overall-conformation, which is stabilized by intramolecular hydrogen bonding. The acidic proton at the nitrogen atom of the central pyrrolic ring is disordered, being observed with half occupancy at two symmetry-equivalent positions off the crystallographic diad. Attempts to remove the disorder by cooling to 97K were unsuccessful, since no indication for a phase transition was detected. 相似文献