Characterization of radiation and autoxidation-initiated damage in DNA model compounds

The damage caused by ionizing radiation and by autoxidation processes to the base moiety of deoxydinucleoside monophosphates d(TpA) and d(GpC) exposed in oxygenated solutions has been investigated. The same principal products are generated by both modalities. The products generated in largest yield have been identified as formamide and imidazolidine modifications derived from damaged thymine and cytosine moieties, respectively. These radiation-induced and autoxidation-induced lesions have been isolated by HPLC and characterized by ¹H NMR spectroscopy including two-dimensional COSY spectroscopy. The possible biological significance of these lesions is discussed.     

Alkylation of pyridinecarbaldehyde oximes with epoxy compounds

O-and N-Alkylation products were obtained by reactions of pyridine-2-,-3-, and-4-carbaldehyde oximes with enantiomerically pure and racemic epoxy compounds (1,2-epoxypropane, 1-phenyl-1,2-epoxyethane, 1-chloro-2,3-epoxypropane, and 1-bromo-2,3-epoxypropane) in the presence of bases and under conditions of phase-transfer catalysis. A series of new amino alcohols was synthesized by condensation of amines with products of O-alkylation of pyridinecarbaldehyde oximes with 1-halo-2,3-epoxypropanes. Published in Russian in Zhurnal Organicheskoi Khimii, 2007, Vol. 43, No. 3, pp. 450–454. The text was submitted by the authors in English.     

若干含氧桥双核钼(V)原子簇化合物的研究

本文在测定了五个新颖双核钼(V)簇合物的晶体结构(QH)4[Mo2O4(NCS)6](1),H(PyH)3.[Mo2O4(C2O4)2(H2O)2]2.2H2O(2), (QH)3[Mo2O4(C4H3OCOO)(NCS)4](3),(QH)3[Mo2O4.(CH2OH)(NCS)5](4)和(PyH)4[Mo2O3(SO4)(NCS)6](5)以及文献报道该类型化合物结构数据的基础上, 综述了含氧桥双核钼(V)簇合物的结构特征, 并应用SCC-EHMO方法探讨了该类型化合物的电子结构和成簇机理, 最后用简征坐标分析法, 研究了含氧桥双核钼(V)化合物簇胳单元[Mo2O4]^2^+和[Mo2O3SO4]^2^+的振动结构及其红外谱带归属。     

Alkylation of aromatic compounds with adamantan-1-ol

Reactions of substituted benzenes, naphthalenes, and 2- and 3-phenyl-1-benzofurans with adamantan-1-ol in trifluoroacetic acid lead to the formation of the corresponding mono-and diadamantylsubstituted aromatic compounds.     

Alkylation of β-dicarbonyl compounds with 1,2-dibromocyclohexane

Alkylation of acetylacetone, ethyl acetoacetate, and diethyl malonate with 1,2-dibromocyclohexane in the presence of K₂CO₃ in DMSO occurs only asC-alkylation accompanied by dehydrobromination, whereas a similar reaction of dimedone follows bothC- andO-alkylation pathways. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 317–319, February, 1998.     

Micellar chromatography of inorganic compounds

Micellar chromatography has been used to separate various compounds and to determine the partition coefficients of the compounds between aqueous bulk solution and a micellar pseudophase. The application of this method to inorganic analyses is less common than its application to organic analyses, albeit the former application gives fundamental aspects of the micellar partition of simple ions and promises developments of novel separation. In this review, we focus our attention on the fundamental aspects of micellar chromatography mostly in inorganic analysis of simple ions.     

Carboxylate ligands drastically enhance the rates of oxo exchange and hydrogen peroxide disproportionation by oxo manganese compounds of potential biological significance

To mimic the carboxylate-rich active site of the manganese catalases more closely we introduced carboxylate groups into dimanganese complexes in place of nitrogen ligands. The series of dimanganese(III,IV) complexes of tripodal ligands [Mn(2)(L)(2)(O)(2)](3+/+/-/3-) was extended from those of tpa (1) and H(bpg) (2) to those of H(2)(pda) (3) and H(3)(nta) (4) (tpa=tris-picolylamine, H(bpg)=bis-picolylglycylamine, H(2)(pda)=picolyldiglycylamine, H(3)(nta)=nitrilotriacetic acid). While 3 [Mn(2)(pda)(2)(O)(2)][Na(H(2)O)(3)] could be synthesized at -20 degrees C and characterized in the solid state, 4 [Mn(2)(nta)(2)(O)(2)](3-) could be obtained and studied only in solution at -60 degrees C. A new synthetic procedure for the dimanganese(III,III) complexes was devised, using stoichiometric reduction of the dimanganese(III,IV) precursor by the benzil radical with EPR monitoring. This enabled the preparation of the parent dimanganese(III,III) complex 5 [Mn(2)(tpa)(2)(O)(2)](ClO(4))(2), which was structurally characterized. The UV/visible, IR, EPR, magnetic, and electrochemical properties of complexes 1-3 and 5 were analyzed to assess the electronic changes brought about by the carboxylate replacement of pyridine ligands. The kinetics of the oxo ligand exchanges with labeled water was examined in acetonitrile solution. A dramatic effect of the number of carboxylates was evidenced. Interestingly, the influence of the second carboxylate substitution differs from that of the first one probably because this substitution occurs on an out-of-plane coordination while the former occurs in the plane of the [Mn(2)O(2)] core. Indeed, on going from 1 to 3 the exchange rate was increased by a factor of 50. Addition of triethylamine caused a rate increase for 1, but not for 3. The abilities of 1-3 to disproportionate H(2)O(2) were assessed volumetrically. The disproportionation exhibited a sensitivity corresponding to the carboxylate substitution. These observations strongly suggest that the carboxylate ligands in 2 and 3 act as internal bases.     

Pairwise exchanges of oxo and imido groups in rhenium(VII) compounds

The kinetic and thermodynamic parameters for the oxo and imido exchange reactions among MeReO(3), MeReO(2)(NR), MeReO(NR)(2), and MeRe(NR)(3) (R = 1-adamantyl, Ad; or 2,6-diisopropylphenyl, Ar) have been measured. The rate constant for the NAr series decreases from 0.27 to 0.0024 L mol(-1) s(-1) at 25 degrees C in benzene as the total number of participating imido groups increases from 2 to 4, indicating that steric effects play an important role in the kinetics of the ligand exchange reactions. But, with NAd, the values of k/L mol(-1) s(-1) are 0.2 (4 NAd), 100 (3 NAd), and 0.74 (2 NAd). The equilibrium constants, also subject to steric effects, are much larger than those predicted by ligand combination statistics and greatly favor the mixed oxo-imido compounds. The different steric demands by imido and oxo ligands are believed to be the main factor for the larger equilibrium constants because the equilibrium constant shows minimal dependence on temperature. The large negative activation entropies for the ligand exchange reactions are consistent with a metathesis mechanism featuring nearly concurrent interchange of oxo and imido groups.