Reaction of ketenes with N,N-disubstituted α-aminomethyleneketones. XX. Synthesis of 2H-pyrano[2,3-f]quinazoline derivatives

The polar 1,4-cycloaddition of dichloroketene to N,N-disubstituted (E)-6-aminomethylene-7,8-dihydro-(2-methyl)(2-phenyl)quinazolin-5(6H)-ones III , prepared in good yields from 7,8-dihydro-(2-methyl)-(2-phenyl)quinazolin-5(6H)-ones via their 6-hydroxymethylene derivatives I and II , gave in satisfactory to excellent yields N-N-disubstituted 4-amino-3,3-dichloro-3,4,5,6-tetrahydro-(8-methyl)(8-phenyl)-2H-pyrano- [2,3,-f]quinazolin-2-ones IV , which are derivatives of the new heterocyclic system pyrano[2,3-f]quinazoline. This cycloaddition occurred both in the case of aliphatic and aromatic N-substitution only with 2-phenyl-enaminones III , whereas with 2-methyl derivatives III the reaction took place only in the case of aromatic N-monosubstitution. Dehydrochlorination of IV with DBN afforded, generally in excellent yields, N,N-disubstituted 4-amino-3-chloro-5,6-dihydro-(8-methyl)(8-phenyl)-2H-pyrano[2,3-y]quinazolin-2-ones, which were dehydrogenated with DDQ to give N,N-disubstituted 4-amino-3-chloro-(8-methyl)(8-phenyl)-2H-pyrano[2,3-f]quinazolin-2-ones in excellent yields.     

Efficient 3D database screening for novel HIV-1 IN inhibitors

We describe the use of pharmacophore modeling as an efficient tool in the discovery of novel HIV-1 integrase (IN) inhibitors. A three-dimensional hypothetical model for the binding of diketo acid analogues to the enzyme was built by means of the Catalyst program. Using these models as a query for virtual screening, we found several compounds that contain the specified 3D patterns of chemical functions. Biological testing shows that our strategy was successful in searching for new structural leads as HIV-1 IN inhibitors.     

Electron impact mass spectrometry of hemiterpenoid tricyclic quinoline alkaloids

The mass spectral behaviour of some quinoline-type alkaloids, 3,4-dihydro-2H,5H-pyrano[3,2-c]quinolin-5-ones, isomeric 3,4-dihydro-2H,5H-pyrano[2,3-b]quinolin-5-ones and 2H,5H-pyrano[3,2-c]quinolin-5-ones, was studied in detail with the aid of linked scans, exact mass measurements and collisional spectrometry. The occurrence of a partial isomerization of the differently annulated isomers to a common, open-chain structure is discussed.     

High-performance liquid chromatographic analysis of chlorophylls, pheophytins and carotenoids in virgin olive oils: chemometric approach to variety classification

This work evaluate the possibility to get from the quali-quantitative determination of the pigments contained in monovarietal olive oils (chlorophylls, pheophytins and carotenoids) and from the multivariate statistical analysis of these measures, parameters able to distinguish within the cultivars. The chemometric variables used have concurred to obtain preliminary interesting results. Liquid-phase distribution and solid-phase extraction/purification procedures has been compared: recoveries for both are resulted higher than 94% for all the pigment classes and the R.S.D. values were below 10%. HPLC analysis, allowing the simultaneous pigment determination, and fluorescence detection, allowing a better green pigments measure (detection limits from 5 to 80ppb), are revealed a fundamental solution.     

Electron impact mass spectrometry of 2-(methoxycarbonylmethyl)-2-phenyl-1,3-benzoxathiole and 2-acetonyl-2-phenyl-1,3-benzoxathiole

The electron impact mass spectrometric behaviour of 2-(methoxycarbonylmethyl)-2-phenyl-1,3-benzoxa-thiole 3a and 2-acetonyl-2-phenyl-1,3-benzoxathiole 3b has been studied in detail. The structures of the more interesting fragment ions have been confirmed with the aid of accurate mass measurements, linked scans and collisional activation experiments. In addition to the ionic species already described in the general fragmentation pattern of 1,3-benzoxathiole derivatives, other fragments arising from the interaction of the carboxy-containing chain with the sulfur atom of these compounds have been observed and evidence presented.     

Pyrolytic behaviour of metal containing compounds in oxygen determination with elemental analyzer

Summary The oxygen determination in organic compounds containing metals with elemental analyzer has been reinvestigated by studying the behaviour during the pyrolytic process, with particular attention to the formation and decomposition of oxides. In order to obtain more satisfactory analytical results the use of particular additives has been examined. The determinations have been performed with a Perkin-Elmer Elemental Analyzer Model 240, by using 50% platinized carbon at 950° C, and with a Carlo Erba Elemental Analyzer Model 1106, by using nickelized carbon at 1050° C.

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Über das pyrolytische Verhalten metallhältiger Verbindungen bei der Sauerstoffbestimmung

Zusammenfassung Die Sauerstoffbestimmung in metallhältigen organischen Verbindungen wurde neuerlich untersucht, besonders hinsichtlich des Pyrolysevorgangs und der dabei stattfindenden Bildung und Zersetzung von Oxiden. Zwecks Erzielung besserer Ergebnisse wurden besondere Zusätze zur Einwaage versucht. Die Bestimmungen wurden mit einem Elemental-Analyzer, Modell 240, von Perkin-Elmer mit 50% platiniertem Kohlenstoff bei 950° C und mit einem Elemental-Analyzer, Modell 1106, von Carlo Erba unter Verwendung von nickelhaltigem Kohlenstoff bei 1050°C ausgeführt.

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Presented at the 9th International Symposium on Microchemical Techniques, Amsterdam, August 28–September 2, 1983.     

On the detailed mechanisms of collision-induced dissociation experiments performed by electrospray ion trap

The product ion spectra obtained by electrospray ionization (ESI) ion trap instruments exhibit a higher number of fragment ions than those achieved by other ion-trap-based systems, indicating the presence of more effective energy deposition mechanisms. This behavior can be attributed to several different reasons, among which different initial internal energy of the precursor ions, pre-activation due to collisions taking place outside the trap, different target gas mixtures inside the trap, and different ion trap geometry were considered. Data obtained from experiments using a triple quadrupole instrument, CI-ion trap, and ESI-ion trap have been compared. The results so achieved seem to indicate that the presence inside the trap of neutral molecules of the solvent employed for the ESI process have a relevant role, promoting high energy deposition in the colliding ions.     

The photochemistry of 4-chlorophenol in water revisited: the effect of cyclodextrins on cation and carbene reactions

The photochemistry of 4-chlorophenol (1) in water and in the presence of cyclodextrins has been studied by means of steady-state and time-resolved experiments. These have shown that 1 undergoes photoheterolysis of the C--Cl bond in the triplet state to yield the 4-hydroxyphenyl cation (3)2 in equilibrium with 4-oxocyclohexa-2,5-dienylidene, (3)3. These triplet intermediates scarcely react with a n nucleophile, such as water, nor abstract hydrogen from this solvent, thus they are long-lived (approximately 1 micros). Specific trapping of both intermediates has been achieved. The cation adds to 2-propenol, k(add) approximately 1.3 x 10(8) m(-1) s(-1), to form the long-lived phenonium ion 11 (with lambda(max) = 290 nm), which then converts to 3-(4-hydroxyphenyl)propane-1,2-diol (10). Carbene (3)3 is trapped by oxygen to give benzoquinone and is reduced by D-glucose (k(q) = 8.5 x 10(6) m(-1) s(-1)) to give the phenoxyl radical (8) and phenol (9). Cyclodextrins have been found to trap the intermediates much more efficiently (k(q) = 9.4 x 10(8) m(-1) s(-1) with beta-CD), which indicates that inclusion is involved. Ground state 1 forms inclusion complexes with 1:1 stoichiometry and association constants of 140 and 300 M(-1) with alpha- and beta-CD, respectively. Complexation does not change the efficiency or the mode of photofragmentation of 1; however, it does influence the course of the reaction because the major portion of the intermediates are reduced to phenol within the cavity (k'(red)> or = 5 x 10(7) s(-1)) either via a radical 8 or via a radical cation 9(+)(.). Under these conditions, neither 2-propenol nor oxygen trap the intermediates to a significant extent.     

Structural elucidation and bioactivity of novel secondary metabolites from Carex distachya

Four new carexanes and a new seco-derivative metabolite have been isolated and characterized from the herbaceous plant Carex distachya Desf. All of the structures have been elucidated on the basis of spectroscopic data. These compounds derive from the cyclization of prenylate stylbenoid precursors. The seco-carexane is formed by a further oxidative cleavage of the C-7-C-8 bond. The absolute configurations have been determined by Mosher's method using appropriate chemical correlations. All of the carexanes A-H have been tested for their phytotoxicity against Lactuca sativa. The bioassays showed an inhibitory effect on seed germination for all compounds described in this report.     

Investigation of various SiC materials by means of EPMA/WDS techniques

The microstructure and compositions of SiC materials from different sources and processing routes were investigated by means of EPMA/WDS and image analysis techniques. The influence of various sources of errors like carbon contamination and spectrometers defocusing on the analysis has been assessed.The presence of dissolved sintering aids, or impurities, and their distributions were investigated by EPMA/WDS. In addition, inhomogeneities, porosity agglomerations and heterogeneous inclusions were found in almost all the SiC materials, which are known to influence the corrosion and mechanical behavior of the material.Quantification of secondary phase contents was performed by means of image analysis, EPMA and, when possible, by density measurement. All methods are affected by errors of difficult assessment. In particular, the EPMA/WDS technique has to handle the problem of non homogeneous volumes of analysis. Two quantitative approaches were attempted, both based on the averaging of many points. In the first, the beam was highly focused. In the second approach, large areas (from 10 to 50 m in diameter) were illuminated. The errors and limits of these methods are discussed and the results compared.