The scavenging capacity of γ-aminobutyric acid for acrolein and the cytotoxicity of the formed adduct

Acrolein is a notorious aldehyde with hazardous impacts on humans.

Alicyclic β- and γ-Amino Acids: Useful Scaffolds for the Stereocontrolled Access to Amino Acid-Based Carbocyclic Nucleoside Analogs

Stereocontrolled synthesis of some amino acid-based carbocyclic nucleoside analogs containing ring C=C bond has been performed on β- and γ-lactam basis. Key steps were N-arylation of readily available β- or γ-lactam-derived amino ester isomers and amino alcohols with 5-amino-4,6-dichloropyrimidine; ring closure of the formed adduct with HC(OMe)3 and nucleophilic displacement of chlorine with various N-nucleophiles in the resulting 6-chloropurine moiety.

2-Vinylpyridine–tris(pentafluorophenyl)borane hexane monosolvate

The title compound, C7H7N·B(C6F5)3·C6H14, was obtained by the stoichiometric reaction of 2-vinylpyridine and tris(pentafluorophenyl)borane in toluene. The formed adduct exhibits a restricted rotation along the B—N bond resulting in an asymmetry, which can be also observed in the19F NMR spectra. The B—N distance is equivalent to the distances found for 2-methylpyridine and 2-ethylpyridine B(C6F5)3adducts. For the final refinement, the contributions of disordered solvent molecules were removed from the diffraction data with SQUEEZE inPLATON[van der Sluis & Spek (1990).Acta Cryst.A46, 194–201; Spek (2009).Acta Cryst.D65, 148–155].

A competitive ELISA detecting 7-methylguanosine adduct induced by N-nitrosodimethylamine exposure

N-Nitrosodimethylamine is a chemical compound known to be carcinogenic to animals and probably to humans. It is widespread and it can be found in food, tobacco smoke and in industrial emissions, such as in the rubber industry. N-Nitrosodimethylamine exerts its biological effects after metabolic activation by forming methylating nucleic acids in DNA. The most formed adduct is 7-methylguanosine. Our laboratory has developed and validated a competitive enzyme-linked immunosorbent assay in order to detect this adduct in DNA exposed to N-nitrosodimethylamine in vitro or in vivo. The imidazole ring-opening (iro) of 7-methylguanosine was required because of its stability. When 7-methylguanosine iro and serum were incubated at 48C, the assay was 35 times more sensitive than at 378C (50% inhibition at 37 fmol 7-methylguanosine iro per well at 48C and 1.28 pmol at 378C) with a lower limit of detection at 1.58 fmol 7-methylguanosine iro. This assay is reproducible, can be routinely performed and is sensitive enough to detect 7-methylguanosine adduct in DNA samples from human exposed to N-nitrosodimethylamine. We aim to use this method in further studies on epidemiological assessment in people at high risk, such as smokers.

Schwefelverbrückte Metallocen/Aluminium-Verbindungen - Isolierung und dynamisches Verhalten von [(MeCp)2ZrS]2 · AlMe3 / Sulfur-Bridged Metallocene/Aluminum Complexes - Isolation and Dynamic Behaviour of [(MeCp)2ZrS]2 · AlMe3

The reaction of cyclodimeric group 4b metallocene sulfides [(RCp)2MS]2 (M = Zr, R = H, Me, tBu: 2a-c; M = Hf, R = H, Me: 2d,e) with trialkylaluminum compounds gives dimeric sulfur-bridged metallocene/aluminum complexes [(RCp)2M(R′)SAlR′2]2 (M = Zr, R = H, Me, tBu, R′ = Me: 3a-c; M = Hf, R = H, Me, R′ = Me: 3d,e, R′ = Et: 3f,g). At low temperature the primarily formed adduct [(MeCp)2ZrS]2 · AlMe3 6 was isolated and its temperature-de-pendent dynamic NMR spectra monitored. The metallocene sulfide/trialkylaluminum addition products exhibit a reaction pattern which indicates the occurrence of reversible alkyl migration between the main group and transition metal center. This may be of relevance for developing novel types of olefin oligomerization catalysts.

Structure and stereochemistry of a 7-phosphabicyclo[2.2.1]hept-2-ene-7-oxide from X-ray, multinuclear NMR, and 2D-J resolved NMR studies

Preparations of a 7-phosphanorbornene, from the reaction of 1,2,5-triphenylphosphole-1-oxide with inhibited acrylonitrile in benzene, were repeated under various conditions to determine if one, or more than one, stereoisomer was formed. Adduct formation failed to occur when the reaction was attempted in ethanol, or when the precursor 1,2,5-triphenylphosphole was substituted for the phosphole oxide. Elemental analysis and spectroscopic measurements confirmed that a 1:1 adduct had been obtained, and an X-ray structure determination of the ethanol complex established that this was 5-cyano-1,4,7-triphenyl-7-phosphabicyclo[2.2.1]hept-2-ene-7-oxide, 3a. Details of the 1H, 13C, and 31P NMR assignments, of potential value in the structural assignment of other similar adducts, are related to previous results. The results of a brief mass spectrometric analysis of the changes in the thermal fragmentation pattern of the adduct with temperature are discussed in relation to the synthetic reaction. Keywords: phosphole adduct, phosphanorbornene, phosphabicycloheptene, acrylonitrile.

REACTION OF OXYGEN ATOMS WITH BENZENE

The reaction of benzene with oxygen atoms produced by mercury photosensitized decomposition of nitrous oxide has been studied in a circulating system at room temperature. The main reaction product is a non-volatile material probably largely aldehydic in character. This is tentatively assumed to result from the rearrangement and polymerization of the initially formed adduct. Smaller amounts of phenol and carbon monoxide are also formed. The rate of formation of carbon monoxide decreases with increasing pressure, suggesting an energy-rich precursor.Oxygen atoms react with benzene much more slowly than with olefines. At 120° cyclopentene reacts about 150 times more quickly than benzene. The activation energy of the reaction of oxygen atoms with benzene has been estimated at 4.6 to 4.9 kcal/mole, with an uncertainty of about 0.7 kcal/mole.