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81.
Mariana Pazos Bruno González Leopoldo Suescun Gustavo Seoane Ignacio Carrera 《Tetrahedron letters》2017,58(23):2182-2185
The enantioselective preparation of three protected β-amino-γ-hydroxyesters from benzoic acid is described. The employed synthetic methodology involves the ipso, ortho cis-dihydroxylation of benzoic acid by the mutant strain Ralstonia eutropha B9, followed by a selective halonium induced beta lactamization. Modification of this novel β-lactam structure by the appropriate sequence of reactions allows for the selective preparation of the aforementioned β-amino-γ-hydroxyesters in a diastereodivergent manner. The overall transformation results in a selective formal aminohydroxylation of the diene moiety of the initial cis-cyclohexadienediol. The synthesized products are important building blocks and will allow for the selective preparation of aminoacids, inosamines and alkaloids from benzoic acid. 相似文献
82.
Avellone G Bongiorno D Buscemi S Ceraulo L Indelicato S Pace A Pibiri I Vivona N 《European journal of mass spectrometry (Chichester, England)》2007,13(3):199-205
The mass spectrometry behavior of 1,2,4-oxadiazolyl-N-methylpyridinium salts has been investigated. These substances are of current interest as perspective ionic liquids, compounds used as green solvents for synthesis, and for their catalytic properties. The studies have been developed through ESI-MS/MS experiments. The obtained results demonstrate that a readily distinction between the two isomeric classes, 3- N-methylpyridinium- and 5-N-methylpyridinium-1,2,4-oxadiazoles, is possible through ESI-MS/MS experiments. A deeper investigation on the principal fragmentation pathways of characteristic ions has been also developed. 相似文献
83.
Leopoldo Ceraulo Pasquale Agozzino Mirella Ferrugia Vincenzo Sprio 《Journal of heterocyclic chemistry》1990,27(2):255-257
A comparison of the behaviour on the nitrosation of the isomers 5-(2-methoxyphenyl)- ( 1a ) 5-(3-methoxyphenyl)- ( 1b ) and 5-(4-methoxyphenyl)2,3-diphenylpyrroles ( 1c ) carried out in the usual way with iso-amyl nitrite in a solution of sodium ethoxide in ethanol evidences that 1a is dramatically less reactive with respect to 1b and 1c . The different reactivity was ascribed to the occurrence of a strong hydrogen bond involving pyrrole N? H and the ortho-methoxy group. 相似文献
84.
High performance liquid chromatography-mass spectrometry based chemometric characterization of olive oils 总被引:1,自引:0,他引:1
Nagy K Bongiorno D Avellone G Agozzino P Ceraulo L Vékey K 《Journal of chromatography. A》2005,1078(1-2):90-97
In this study the effective discrimination of extra virgin olive oils is described using HPLC-MS, combined with chemometric evaluation. The presented method is simple since the diluted oil sample is directly injected into the system, without any preliminary chemical derivatization or purification step. Separation of diacylglycerols, triacylglycerols and sterols occurs within 20 min and is achieved using an octadecyl-silica column. Detection is performed by positive APCI mass spectrometry which provided sensitivity to detect over 50 compounds in the sample. After extraction of data, stepwise discriminant function analysis is used to select the variables with the highest discriminative power. These variables are used to perform linear discriminant analysis and classify/predict the samples. One-hundred per cent classification and 99% prediction rate was achieved for olive oils obtained from Nocellara, Biancolilla and Cerausola cultivars. Reliability of prediction was tested by cross validation. 相似文献
85.
Ultraweak Photon Emission from the Seed Coat in Response to Temperature and Humidity—A Potential Mechanism for Environmental Signal Transduction in the Soil Seed Bank 下载免费PDF全文
Steven Footitt Simonetta Palleschi Eugenio Fazio Raffaele Palomba William E. Finch‐Savage Leopoldo Silvestroni 《Photochemistry and photobiology》2016,92(5):678-687
Seeds beneath the soil sense the changing environment to time germination and seedling emergence with the optimum time of year for survival. Environmental signals first impact with the seed at the seed coat. To investigate whether seed coats have a role in environmental sensing we investigated their ultraweak photon emission (UPE) under the variable temperature, relative humidity and oxygen conditions they could experience in the soil seed bank. Using a custom‐built luminometer we measured UPE intensity and spectra (300–700 nm) from Phaseolus vulgaris seeds, seed coats and cotyledons. UPE was greatest from the internal surface of the seed coat. Seed coat UPE increased concomitantly with both increasing temperature and decreasing relative humidity. Emission was oxygen dependent and it was abolished by treatment with dinitrophenylhydrazine, demonstrating the key role of seed coat carbonyls in the phenomenon. We hypothesize that beneath the soil surface the attenuation of light (virtual darkness: low background noise) enables seeds to exploit UPE for transducing key environmental variables in the soil (temperature, humidity and oxygen) to inform them of seasonal and local temperature patterns. Overall, seed coats were found to have potential as effective transducers of key fluctuating environmental variables in the soil. 相似文献
86.
Silvia Russi Leopoldo Suescun Alvaro Mombrú Helena Pardo Raúl A. Mariezcurrena Gabriel Cavalli Gustavo Seoane 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(7):820-821
The title compound, [Fe(C8H11ClO2)(CO)3], has been synthesized, isolated and characterized by single‐crystal X‐ray diffraction. The molecule crystallizes in the orthorhombic space group P212121. The metal–ligand arrangement is typical of (1,3‐diene)tricarbonyliron complexes. 相似文献
87.
Leopoldo Suescun Alvaro W. Mombrú Raúl A. Mariezcurrena Helena Pardo Silvia Russi Ricardo Baggio 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(2):179-181
The crystal structure of the title compound, [NiCl(C12H8N2)2(CH4N2S)]2(NO3)Cl·2C2H6O, is formed by [Ni(phen)2(thiourea)Cl]+ cations (phen = 1,10‐phenanthroline), chloride and nitrate counter‐ions, and ethanol solvate molecules. The Ni atom is octahedrally coordinated to two bidentate phen ligands, a monodentate thiourea and a chloride ion. Both the chloride and nitrate anions, which provide charge balance, are located at special positions on a twofold symmetry axis. Hydrogen bonds play a key role in the packing and conformation of the cation and create a three‐dimensional network. 相似文献
88.
D Bongiorno L Ceraulo A Mele W Panzeri A Selva V T Liveri 《Journal of mass spectrometry : JMS》2001,36(11):1189-1194
Ionspray (IS) and fast atom bombardment (FAB) positive ionization mass spectrometry (MS) of 1 : 1 beta-cyclodextrin (beta-CD)-melatonin (MLT) host-guest complex allowed the detection of gaseous protonated 1 : 1 beta-CD-MLT. Tandem MS collision-induced dissociation (CID) of such protonated 1 : 1 beta-CD-MLT species showed the proton (charge) to be retained to a significant extent by the host and by its cage fragmentation products, in spite of the higher proton affinity of MLT with respect to that of beta-CD. This requires an endothermic guest-to-host proton transfer to occur within the gaseous association. Collisional activation could be accounted for by the promotion of such an endothermic process; however, the proton affinity decrease of the guest determined by the loss of the elements of acetamide, which is a dominant MS dissociation reaction of pure protonated MLT, could also provide a rationale for such an endothermic guest-to-host proton transfer. This proposal parallels the reaction scheme we had previously formulated for the analogous MS and tandem MS behaviour of 1 : 1 beta-CD-5-methoxytryptamine inclusion complex with the protonated 5-methoxytryptamine guest undergoing deamination. 相似文献
89.
Eleonora Freire Sergio Baggio Leopoldo Suescun Ricardo Baggio 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(8):905-908
Three cis nickel–dithiocyanate (SCN) complexes with different N,N′‐bidentate bases have been prepared and their crystal structures determined: bis(2,2′‐bipyridine‐N,N′)bis(thiocyan‐ato‐N)nickel(II), [Ni(SCN)2(C10H8N2)2], bis(1,10‐phenanthroline‐N,N′)bis(thiocyanato‐N)nickel(II), [Ni(SCN)2(C12H8N2)2], and bis(2,9‐dimethyl‐1,10‐phenanthroline‐N,N′)bis(thiocyanato‐N)nickel(II) monohydrate, [Ni(SCN)2(C12H8N2)2]·H2O. Distortions due to ligand size are discussed. 相似文献
90.