Reaction of N-phenylbenzamidrazone with cis-1,2-cyclohexanedicarboxylic anhydride

An analysis of the products of the reaction of N³-phenylbenzamidrazone with cis-1,2-cyclohexanedicarboxylic anhydride at various temperatures is presented. The identification of the reaction products is carried on with the support of computational techniques. The most stable conformers of the isoindole and triazole derivatives are found within the DFT approach. The theoretical calculations reveal the possible structure of a triazole derivative not available experimentally because of the presence of two diastereoisomers of equal energy.     

Well-Defined Aminophenolate Zinc and Magnesium Complexes as Excellent Inhitiators for the ROP of Lactides

A series of molecular homo and heteroleptic zinc and magnesium compounds with aminophenolate ligands [(µ,η²-L²)ZnEt]₂ ( 1 ), [(η²-L²)Zn(µ-BnO)]₂ ( 2 ), [Zn(η²-L²)₂] ( 3 ), [Zn(η²-L³)₂] ( 4 ), [Mg(η²-L³)₂] ( 5 ) (L²-H = N-[methylene(2-hydroxy-3,5-di-tert-butylphenyl)]-N-methyl-N-cyclohexylamine, L³-H = N-[methylene(2-hydroxy-3,5-di-tert-butylphenyl)]-N-methyl-N-methyl-1,3-dioxolaneamine) have been prepared and characterized. The homoleptic complexes 3–5 are most probably a mixture of diastereoisomers that in solution show an interesting dynamics which plays an important role in their catalytic behavior. The complexes 2 – 5 are efficient initiators in ring-opening polymerization (ROP) of lactides to produce polymers with desired molecular weight and narrow polydispersity.     

Influence of heavy metals, especially lead, on lipid metabolism, serum alpha-tocopherol level, total antioxidant status, and erythrocyte redox status of copper smelter workers

An assessment of influence of the occupational exposure to heavy metals, especially lead, on serum lipids (including lipid peroxides), total antioxidant status, erythrocyte redox status, and serum alpha-tocopherol level was performed in a group of 141 healthy male copper smelter workers. The following parameters were measured: blood lead and cadmium levels, serum manganese, copper, zinc, calcium and magnesium levels, free erythrocyte protoporphyrins (FEP), total cholesterol, HDL₂-, HDL₃-cholesterol, triglycerides and lipid peroxides in serum, erythrocyte superoxide dismutase (SOD_E), catalase (Cat_E) and glutathion peroxidase (PxGSH_E) activities, erythrocyte reduced glutathione level (GSH_E), serum alpha-tocopherol level, and serum total antioxidant status (TAS). Mean Pb_B was within the norm range (328.2 ± 141.7 μg/L), but mean Mn_S concentration slightly exceeded 10 μg/L (11.04 ± 3.79 μg/L). Mean cholesterol and triglycerides concentrations were near the highest borderline values. We found a significantly negative correlation between lead levels and HDL₃-cholesterol (r = 0.253, P < 0.05). Erythocyte catalase activity and TAS were lowered. TAS showed significant negative correlation with Pb_B. A group of workers with Pb_B≥ 400 μg/L had significantly lower Cat_E, lower TAS, and lower HDL₃-cholesterol, compared to the workers with Pb < 400 μg/L. We have also found positive correlation between alpha-tocopherol and total cholesterol (r = 0.267, P < 0.05) and between alpha-tocopherol and LDL-cholesterol (r = 0.207, P < 0.05). Received: 28 July 1997 / Revised: 6 November 1997 / Accepted: 4 November 1997     

Chromogenic azole diazothiacrown ethers

Azocrown ethers with sulphur atoms and pyrrole or imidazole residue as a part of macrocycle have been synthesised. Their metal complexation abilities in acetonitrile were studied using UV–vis spectrophotometry. The largest spectral changes were observed for both pyrrole- and imidazole-azothiacrown ethers on complexation with Pb^2 + , Cu^2 + , Zn^2 + , Ni^2 + , Co^2 +  and Ag⁺ ions. In the case of alkali and alkaline earth metal ions no spectral changes were found. Preliminary studies of ion-selective membrane electrodes with synthesised ionophores are presented. In the measurement for transition/heavy metal cations, only copper and lead give high responses. X-ray structure of 18-membered pyrrole azothiacrown ether is described.     

Planarity of heteroaryldithiocarbazic acid derivatives showing tuberculostatic activity. III. Mono‐ and diesters of 3‐(pyrazin‐2‐ylcarbonyl)dithiocarbazic acid

Methyl 2‐(pyrazin‐2‐ylcarbonyl)hydrazinecarbodithioate, C₇H₈N₄OS₂, (E1), N′‐[bis(methylsulfanyl)methylidene]pyrazine‐2‐carbohydrazide, C₈H₁₀N₄OS₂, (F1), N′‐[bis(methylsulfanyl)methylidene]‐6‐methoxypyrazine‐2‐carbohydrazide, C₉H₁₂N₄O₂S₂, (F2), and methyl 1‐methyl‐2‐(pyrazin‐2‐ylcarbonyl)hydrazinecarbodithioate, C₈H₁₀N₄OS₂, (G1), can be considered as derivatives of classical (thio)amide‐type tuberculostatics, and all are moderately active against Mycobacterium tuberculosis. This study was undertaken in a search for relationships between activity and specific intramolecular interactions, especially conjugations and hydrogen‐bond contacts, and the molecular structures were compared with respective amine analogues, also active against the pathogen. Despite the differences between the amine and carbonyl groups with opposite functions in the hydrogen bond, the two types of structure show a surprisingly similar planar geometry, mostly due to the conjugations aided by the bifurcated intramolecular hydrogen‐bond contact between the N—H group of the central hydrazide group as donor and a pyrazine N atom and an S atom of the dithio function as acceptors. Planarity was suggested to be crucial for the tuberculostatic activity of these compounds. The N‐methylated derivative (G1) showed a significant twist at the N—N bond [torsion angle = −121.9 (3)°] due to the methyl substitution, which precludes an intramolecular N—H...S contact and the planarity of the whole molecule. Nonetheless, the compound shows moderate tuberculostatic activity.     

LC Separation of Fatty Acid Ceramides Using a Two Column System

Type II ceramides were separated according to the length of their fatty acid alkyl chain using two column system. The packing of the first column was non-polar adsorbent prepared by coating of macroporous spherical silica with cationized poly(vinyl alcohol) of low substitution degree. Commercial normal phase column Lichrosorb Si 60 was used as a second column in this system. Elution was performed in an isocratic mode using methanol:chloroform 50:50 (v/v) as an eluent.