On the Allylic Oxidation of Ent-kaurenic Acid Methyl Ester with Lead Tetra-acetate.

In this paper, results obtained upon treatment of the methyl ester of ent-kaur-16-en-19-oic acid (1b) with lead tetra-acetate under reflux in glacial acetic acid solution and an argon atmosphere are described. After 30 minutes reflux, GC-MS analysis of the product indicated the presence of three substances, the initial compound (1b, 7 %), the methyl ester of ent-kaur-16-en-15-O-acetyl-19-oic acid (2a, C₂₃H₃₀0₄, 45 %), and its isomer, the methyl ester of ent-kaur-15-en-17- 0-acetyl-19-oic acid (3a, 47 %). Flash chromatography over silica gel containing 20% AgNO₃ yielded 2b (456 mg), which was identified by direct comparison with an authentic sample, and 3a (472 mg), whose structure was established by uni- and bi-dimensional NMR analysis.

Essential Oil Composition and Antibacterial Activity of Hyptis colombiana from the Venezuelan Andes.

Hyptis colombiana is an aromatic shrub native to the Colombian and Venezuelan Andes. Aerial parts were collected in Mérida State at about 3100 m above sea level in February 2005, and May and October 2006. The essential oil was found to contain germacrene D and β-caryophyllene as main constituents (about 50%).

Chemical composition and antibacterial activity of the essential oil of Ruilopezia bracteosa.

The essential oil from the leaves ofRuilopezia bracteosa was obtained by hydrodistillation, and analyzed by GC-MS. Eighteen components, which made up 99.6% of the oil were identified, the most abundant being β-myrcene (34.

Dreaming in Spain: Parental Determinants of Immigrant Children's Ambition.

We examine determinants of educational and occupational aspirations and expectations among children of immigrants in Spain on the basis of a unique data set that includes statistically representative data for foreign-origin secondary students in Madrid and Barcelona plus a sample of one-fourth of their parents. Independently collected data for both generations allow us to establish effects of parental characteristics on children's orientations without the confounding potential inherent in children's reports about parents. We analyze first determinants of parental ambition and, through a series of step-wise regressions, the effects of these goals and other parental and family characteristics on children's aspirations and expectations.

Chemical composition and antibacterial activity of the essential oil of Espeletia nana.

The essential oil of the leaves of Espeletia nana Cuatrec., obtained by hydrodistillation, was analyzed by GC-MS, which allowed the identification of 24 components, which made up 99.9% of the oil.

Drug delivery properties of macroporous polystyrene solid foams.

Purpose: Polymeric porous foams have been evaluated as possible new pharmaceutical dosage forms.

Methods: These materials were obtained by polymerization in the continuous phase of highly concentrated emulsions prepared by the phase inversion temperature method. Their porosity, specific surface and surface topography were characterized, and the incorporation and release of active principles was studied using ketoprofen as model lipophilic molecule.

Coming of age in Spain: the self-identification, beliefs and self-esteem of the second generation.

We review the literature on determinants of ethnic/national self-identities and self-esteem as a prelude to examining these outcomes among a large, statistically representative sample of second generation adolescents in Madrid and Barcelona. While these psycho-social outcomes are malleable, they still represent important dimensions of immigrant adaptation and can have significant consequences both for individual mobility and collective mobilizations. Current theories are largely based on data from the USA and other Anglophone countries.

On the isomerization of ent-kaurenic acid.

Kaurenic acid (1a) is a tetracyclic diterpene that has an exocyclic double bond at delta16. Isokaurenic acid (2a) has an endocyclic delta15double bond. This compound has been isolated from Espeletia tenore (Espeletinae), a resinous plant from the Venezuelan Andes, but its occurrence is rare.

Chemical composition and antibacterial activity of the essential oil from fruits of Bursera tomentosa.

The hydrodistilled oil from the fruits of Bursera tomentosa, obtained in 0.2% yield, was analyzed by GC-MS. Nine components were identified, which made up 99.

Moving Ahead in Madrid: Aspirations and Expectations in the Spanish Second Generation.

This paper examines determinants of aspirations and expectations among children of immigrants based on a statistically representative sample of 3,375 second generation youths interviewed in 101 public and private secondary schools in metropolitan Madrid. We review the past literature on status attainment in general and aspirations and expectations, in particular, and draw from it a set of six hypotheses to guide the analysis. Most theoretical statements in this field have been developed on the basis of U.

In vitro studies of the hemolytic activity of microemulsions in human erythrocytes.

Hemolytic activity in human erythrocytes as alternative to in vivo testing was used as a potential screening method to evaluate irritant potential of microemulsions for possible application in pharmaceutical and cosmetic formulations. Microemulsions were prepared by mixing surfactants and oil and slowly titrating the mixtures with aliquots of phosphate buffer saline or water. All microemulsions were characterized by dynamic light scattering to determine both the mean droplet size and droplet distribution.