A convenient approach to novel symmetric bispyrimidine diamines comprises SNAr reactions of 4-fluoropyrimidine N-oxide with alkane-α,ω-diamines with subsequent reduction of N-oxide function. The obtained substances were tested in patch-clamp experiments for the influence on the kainateinduced currents in Purkinje neurons and showed negative modulating effect.相似文献
5, 6, 11, 12-Tetrabromo-5, 6, 11, 12-tetrahydrodibenzo[a, e]cyclooctene, C16H12Br4, crystallizes in monoclinic space group P21/c witha=8.6917(7),b=15.135(2),c=12.892(2) Å, =101.836(8)°, V=1660.0(7) Å3,Z=4. The structure was refined toR=0.058 for 3137 observed reflections. The molecule has approximate C2 symmetry, with the eight-membered ring adopting the twist-boat conformation. The planes of the two phenyl rings form a dihedral angle of 117.3(2)°, C–Br distances range 1.965(5)–1.981(5) Å. 相似文献
Chromium nitride and chromium oxide were deposited by arc PVD and APS on steel substrates to be worn in a testing set up simulating the abrasion process of a screw rotor compressor. The damage of CrxN is more severe than that of Cr2O3. The abrasive particles were collected on glassy carbon with a Batelle impactor and analyzed by AES and REM. Particles from the CrxN coating are totally oxidized, in contrast to particles from Cr2O3 which are not chemically influenced. No oxidation can be detected on the surface of the treated CrxN coating. The Cr2O3 coating is not affected either.Dedicated to Professor Dr. rer. nat. Dr.h.c. Hubertus Nickel on the occasion of his 65th birthday 相似文献
The reactions of 1,1-diacetylcyclopropane (1) with a number of hydrazine and hydroxylamine derivatives proceed via cyclopropane ring opening with incorporation of external nucleophile (solvent) to give the 4-β-X-ethyl derivatives of 3,5-dimethylpyrazoles and -isoxazoles, a novel route to these heterocycles. This ring cleavage occurs especially smoothly in water as a solvent. A rationale for this unusually mild nucleophilic cyclopropane ring opening is discussed. 相似文献
Primary and secondary phosphines add regio- and stereospecifically to phenylcyanoacetylene and 4-hydroxy-4-methylpent-2-ynenitrile under mild conditions to form corresponding functionalized secondary and tertiary phosphines of Z-configuration in 70-91% yield. According to ESR and UV data, the addition of primary phosphines to phenylcyanoacetylene involves a single electron transfer process. 相似文献
A heat-stable enzyme was isolated from the cellulase complex of a thermophilic strain of the micromyceteThielavia terrestris. The purified enzyme exhibited both endoglucanase and xylanase activities and had a mol mass of 69,000 Daltons and an isoelectric
point of 6.4. When the cells were grown at 48°C, the initial activity of the purified enzyme using carboxymethylcellulose
as a substrate was 150 nkat/mg and the Michaelis constant was 6.6 g/L. The heat stability of the enzyme was high, losing only
20% of the initial activity after a 6-h incubation at 65 °C. When cultures were grown on microcrystalline cellulose and xylose
was added after 48 h of growth, endoglucanase and xylanase activities were more than doubled. Similar increases in these activities
were observed by growing the cultures on straw. 相似文献
Single crystal X-ray diffraction analyses of calix[4]arene-bis-crown-6 (1) and calix[4]arene-bis-benzocrown-61,2-dichloroethane (2) are reported. Thesestructures offer an opportunity to study the conformation of calix[4]arene-bis-crown-6 molecules in the absence of solvent, and when very weakly solvated. These structures exhibit different conformations of the crown ring, and limited flexibility of the calix[4]arene,but do not show solvent or crown inclusion in the calix[4]arene cavity. Comparisons to similar structures are made, and the implications for cesium binding are discussed. 相似文献
We describe an efficient synthesis of thia analogues of the vitamin D side chain that is based on the in situ generation of a thiolate anion and its alkylation with electrophiles. 相似文献
A versatile one‐step two‐component cyclization to build new tetracyclic nitrogen heterocycles is described. Ortho‐methylhetarenecarbonitrile components were condensed with aldehydes to access a large library of differently substituted ring systems. The heterocyclic core can be easily modified by variation of the position of the endocyclic nitrogen atom in the o‐methylhetarenecarbonitrile substrate. The manner of the nucleophilic attack that leads to the condensation can be triggered by different electron‐density distribution in the molecule induced by the position of the nitrogen atom. Taking this into account, there is an electronic preference that leads to either pyridophenanthrolines or the corresponding pyridoazacarbazoles as the main products. We demonstrate the high antitumor potential of some of our synthesized heterocycles, which is strongly dependent on the substitution pattern introduced through the aldehyde component. The position and number of endocyclic nitrogen atoms play an important role regarding cytotoxicity of the studied compounds. 相似文献