Confirmation of the absolute configuration of tenvermectin B by single-crystal X-ray diffraction analysis of its furan formate derivative.

Tenvermectins A and B are a kind of 16-membered macrocyclic lactone antibiotics with potent insecticidal property, which have been obtained from two genetically engineered strains Streptomyces avermitilis MHJ1011 and S. avermitilis AVE-H39. Aiming at confirming the absolute configuration of tenvermectin B by X-ray diffraction method, 4″, 5 -di-(2-furoyloxyl) tenvermectin B (1) was prepared and a suitable crystal of 1 was obtained from MeOH. The absolute configuration of 1 was unambiguously established by single-crystal X-ray diffraction analysis. The determination of the stereochemistry of tenvermectin B could promote its chemical and biological studies as agricultural and veterinary agents. In addition, compound 1 displayed weak acaricidal and nematocidal activities against Tetranychus cinnabarinus and Bursaphelenchus xylophilus respectively.

Copper mediated C-H amination with oximes: en route to primary anilines.

Here we report an efficient Cu(i)-mediated C-H amination reaction with oximes as amino donors to introduce NH2 groups directly. Various strongly coordinating heterocycles including quinoline, pyrimidine, pyrazine, pyrazole and triazole were tolerated well. The potential utility was further demonstrated in a late-stage modification of telmisartan (an antagonist for the angiotensin II receptor).

Study on the binding interaction of chromium(VI) with humic acid using UV-vis, fluorescence spectroscopy and molecular modeling.

In this report, the binding interaction of chromium(VI), as Cr2O7(2-), with humic acid was studied by using UV-visible absorption, fluorescence spectroscopy, and molecular modeling method. The fluorescence spectral data indicated that the binding interaction existed between Cr2O7(2-) and humic acid and the order of magnitude of binding constants were 10(3). The rise in temperature caused a decrease in the values of the binding constant of humic acid with Cr2O7(2-). Thermodynamic analysis presented that multi-intermolecular forces including hydrogen bonding, hydrophobic, and electrostatic forces were involved in the binding process at pH 6.5. The spectral data also indicated that Cr2O7(2-) affected the aromatic ring structures in humic acid. Furthermore, the molecular modeling analysis indicated that a lot of reactive groups and binding cavities in HA played a key role in its binding with Cr2O7(2-).