Synthesis of heterocyclic compounds IV1 pyrazol-1′-ylpyridines2

2-Pyrazol-1-ylpyridines were synthesized by condensation of pyridylhydrazines with 1,3-dicarbonyl compounds or by theUllmann arylation of pyrazoles with halopyridines.Taken in part from the Master's thesis ofA. A. A. Pinto, Instituto Militar de Engenharia, Rio de Janeiro, 1978.     

Efficient synthesis of the glucosidase inhibitor blintol, the selenium analogue of the naturally occurring glycosidase inhibitor salacinol

An efficient synthesis of blintol, the selenium congener of the naturally occurring glycosidase inhibitor salacinol, and a potent glucosidase inhibitor itself, is described. Unlike our previously reported synthesis, this improved route makes use of p-methoxybenzyl ether protecting groups in the synthesis of one of the two key intermediates, 2,3,5-tri-O-p-methoxybenzyl-1,4-anhydro-4-seleno-D-arabinitol, from L-xylose. The other key intermediate, 2,4-O-benzylidene-L-erythritol-1,3-cyclic sulfate, was successfully prepared from D-glucose instead of the expensive L-glucose. All protecting groups in the resulting adducts were removed with trifluoroacetic acid to yield a mixture of stereoisomers, thereby obviating the problematic deprotection of benzyl ethers by hydrogenolysis. The major stereoisomer, blintol, was then obtained by fractional crystallization.     

Homological algebra for the representation Green functor for abelian groups

In this paper we compute some derived functors of the internal homomorphism functor in the category of modules over the representation Green functor. This internal homomorphism functor is the left adjoint of the box product.

When the group is a cyclic -group, we construct a projective resolution of the module fixed point functor, and that allows a direct computation of the graded Green functor .

When the group is , we can still build a projective resolution, but we do not have explicit formulas for the differentials. The resolution is built from long exact sequences of projective modules over the representation functor for the subgroups of by using exact functors between these categories of modules. This induces a filtration which gives a spectral sequence which converges to the desired functors.

     

An Almost Prime Element in a Commutative Radical Banach Algebra

Thomas conjectured that there is no such thing as an almostprime element in a commutative radical Banach algebra. Thispaper shows that there is such an element. However, it stillleaves open the question of whether there is an element thatis almost prime, but not prime. 2000 Mathematics Subject Classification46J40, 46J45.     

Rainfalls during great Forbush decreases

Summary The changes of rainfall values during great Forbush decreases recorded by the low-latitudinal neutron monitor of Huancayo (47 events from 1956 through 1992) were examined. The data on precipitations were taken from the State of S?o Paulo and from the Amazonian region, Brazil. As a rule, the data from more than 50 meteorological stations were used for each events. The main result is the following: during strong decreases of cosmic-ray flux in the atmosphere (great Forbush decreases) the precipitation value is decreased. The effect of rainfall changes is seen more distinctly if wet seasons are considered.     

Isolation and structural determination of xerophytolic acid A, a 3-geranyl-4-hydroxybenzoate derivative from Xerophyta plicata

A novel compound of a rare class of secondary metabolites, 3-geranyl-4-hydroxybenzoic acid derivative, methyl xerophytolate A (2), was isolated from the crude extract of Xerophyta plicata (Velloziaceae) collected in Rio de Janeiro, Brazil. The structure of 2 was elucidated using spectroscopic methods.     

On the difficulties of predicting the adsorption of volatile organic compounds at low pressures in microporous solid: the example of ethyl benzene

Adsorption isotherms of toluene and ethyl benzene, at 25 degrees C and 40 degrees C, were determined in two microporous activated carbons and one zeolite. Significant differences were found in the adsorption behavior, at low pressures, between the two vapors on the same adsorbent material. The quantities of adsorbed ethyl benzene at 25 degrees C, in the low-pressure region, were lower than what was observed at 40 degrees C in all the studied adsorbents, contrary to what was found for toluene. This fact was not related to kinetic effects at the two temperatures nor to vapor swelling of the adsorbents structure. Also, there was no molecular sieving since at high pressures the toluene and ethyl benzene occupied the same adsorption space. The differences found in the ethyl benzene adsorption at the two temperatures pose difficulties in the analysis of the adsorption data and, therefore, in the prediction of results. This is discussed in the analysis of the results with the application of the Dubinin-Astakhov equation and in the estimation of the isosteric heats of adsorption. The adsorption potentials of two possible ethyl benzene conformations were estimated for the adsorption in the pores of activated carbon from the Horvath and Kawazoe model, and the values compared with those found experimentally. The results were interpreted in terms of the ethyl benzene conformation effects when the molecule is confined in pores that are about the same size of one of the conformations.     

Determination of anatoxin-a in environmental water samples by solid-phase microextraction and gas chromatography-mass spectrometry

In the present work, a method was developed and optimized aiming at the determination of anatoxin-a in environmental water samples. The method is based on the direct derivatization of the analyte by adding hexylchloroformate in the alkalinized sample (pH = 9.0). The derivatized anatoxin-a was extracted by a solid-phase microextraction (SPME) procedure, submersing a PDMS fiber in an amber vial for 20 min under magnetic stirring. GC-MS was used to identify and quantify the analyte in the SIM mode. Norcocaine was used as internal standard. The following ions were chosen for SIM analyses (quantification ions in italics): anatoxin-a: 191, 164, 293 and norcocaine: 195, 136, 168. The calibration curve showed linearity in the range of 2.5-200 ng/mL and the LOD was 2 ng/mL. This method of SPME and GC-MS analysis can be readily utilized to monitor anatoxin-a for water quality control.