Concerning the reactivity of dioxiranes. Observations fromexperiments and theory

The challenging hypothesis of a “biphilic” (i.e., electrophilic vs nucleophilic) character for dioxirane reactivity, which envisages that electron-poor alkenes are attacked by dioxiranes in a nucleophilic fashion, could not be sustained experimentally. Rate data, which estimate Hammett “rho” values for the epoxidation of 3- or 4-substituted cinnamonitriles XâPhsCHdCHsCN, unequivocally allow one to establish that dioxiranes epoxidize electrophilically even alkenes carrying electron-withdrawing groups. The greater propensity of methyl(trifluoromethyl)dioxirane TFDO (1b) to act as an electrophilic oxidant with respect to dimethyldioxirane DDO (1a) parallels the cathode reduction potentials for the two dioxiranes, as measured by cyclic voltammetry. A simple FMO approach for alkene epoxidation is helpful to conceive a likely rationale for the greater oxidizing power of TFDO as compared to DDO

Identification of unique cardiolipin and monolysocardiolipin species in Acinetobacter baumannii

Acidic glycerophospholipids play an important role in determining the resistance of Gram-negative bacteria to stress conditions and antibiotics. Acinetobacter baumannii, an opportunistic human pathogen which is responsible for an increasing number of nosocomial infections, exhibits broad antibiotic resistances. Here lipids of A. baumannii have been analyzed by combined MALDI-TOF/MS and TLC analyses; in addition GC-MS analyses of fatty acid methyl esters released by methanolysis of membrane phospholipids have been performed. The main glycerophospholipids are phosphatidylethanolamine, phosphatidylglycerol, acyl-phosphatidylglycerol and cardiolipin together with monolysocardiolipin, a lysophospholipid only rarely detected in bacterial membranes. The major acyl chains in the phospholipids are C16:0 and C18:1, plus minor amounts of short chain fatty acids. The structures of the cardiolipin and monolysocardiolipin have been elucidated by post source decay mass spectrometry analysis. A large variety of cardiolipin and monolysocardiolipin species were found in A. baumannii. Similar lysocardiolipin levels were found in the two clinical strains A. baumannii ATCC19606(T) and AYE whereas in the nonpathogenic strain Acinetobacter baylyi ADP1 lysocardiolipin levels were highly reduced

Unexpected 2-ethyl-functionalisation of 1,3-dimethylimidazol-2-ylidene with dimethylcarbonate: Use of the reaction system in organocatalysis.

Imidazolium based Ionic Liquids (IL) and salts find application in a wide variety of fields including catalysis and advanced materials. We report here the reaction of 1,3-dimethylimidazolium-2-carboxylate with dimethylcarbonate (DMC) at temperatures ranging from 180 to 200 °C to yield 2-ethyl-1,3-dimethylimidazolium methyl carbonate salt (yield of 75 %).The 1,3-dimethylimidazolium-2-carboxylate /dimethylcarbonate reaction system has been employed in the synthesis of 1,7-heptanedioic acid dimethyl ester from cyclohexanone and DMC

Characterization of isolated 1-aza-adamantan-4-one (C9H13NO) from microwave, millimeter-wave and infrared spectroscopy supported by electronic structure calculations

We have synthesized 1-aza-adamantan-4-one (C9H13NO) starting from commercial 1,4-cyclohexanedio nemonoethylene acetal and tosylmethylisocianide, following a procedure already described in the liter-ature. The high degree of sample purity was demonstrated by gas chromatography and mass spectromet-ric measurements and its structure evidenced by 1H and 13C NMR spectroscopy. Among numerous interests in physical chemistry, this target molecule is of high relevance for mechanistic evaluation and the synthesis of novel pharmaceutical compounds. We present a thorough spectroscopic study of this molecule by gas phase vibrational and rotational spectroscopy. Accurate vibrational frequencies have been determined from infrared and far-infrared spectra. The pure rotational spectrum of the molecule has been recorded both by cavity-based Fourier transform microwave spectroscopy in the 2–20 GHz region by supersonically expanding the vapor pressure of the warm sample and by room-temperature absorption spectroscopy in the 140–220 GHz range. Accurate sets of rotational and centrifugal distortion parameters of 1-aza-adamantan-4-one in its ground state and in five vibrationally excited states have been derived from these measurements and compared to accurate quantum chemical calculations. The hyperfine parameters have been discussed in terms of molecular structure around the nitrogen quadru-pole nucleus