In laboratory trials an aqueous solution of Piquerol A from Piqueria trinervia, collected in several regions of Mexico, showed a molluscicide action on the adults of eight different pulmonates snails species: Fossaria (Fossaria) humilis, F. (Bakerilymnaea) sp., Pseudosuccinea columella and Stagnicola attenuata from Mexico; F. (B.) cubensis and Physa cubensis from Cuba; P. columella and Biomphalaria glabrata from Brazil; B. glabrata from Puerto Rico; and S. elodes from U.S.A. The solution was tested at 50, 25 and 5 ppm concentration, for two periods of 6 and 24 hours, at room temperature (20-22 degrees C). A 100% mortality was obtained for all species at 50 ppm concentration after 6 hours of exposure; the same percentage at 25 ppm after 24 hours; and 60 to 100% mortality at 5 ppm concentration during 24 hours of exposure. No recovery was observed among any of the treated snails. Piquerol A is a sesquiterpene with low stability in nature and has previously only been tested as an insecticide and as an inhibitor of metabolism in cell cultures: no field trails have been made on its toxicity to other aquatic fauna as yet, but it is believed Piquerol A could be an excellent molluscicide for use in areas where focal transmission of schistosomiasis and fascioliasis are taking place. This is the first time experiments on molluscicides have been carried out in Mexico.
The search for new materials possessing high nonlinear optical activities surpassing those of the materials already in the market was extensively pursued during the last decades due to their wide range of applications in secondand third-harmonic generation2, optical bistability3'4 and phase conjugation.5 We have been investigating the structures of a number of monomeric precursors having a central vinyl group and one side a pyridyl ring and on the other side an aliphatic chain, an aromatic or an heterocyclic ring, in connection with a project on solidstate polymerization and towards the electrooptical activity of these compounds. The crystal structure of 5-ethyl-2-pyridylvinylbenzene was studied in connection with the above-mentioned project. Details concerning the chemical synthesis and spectral data using IR and NMR techniques will be reported somewhere. The molecular structure of the title compound is shown in Fig. 2; it has a phenyl ring located at C7 trans to the Table 1 Crystal and experimental data Fig. 2 Molecular structure of the title compound with atom labeling. Thermal ellipsoids are drawn at the 50% probability level. Fig. 3 Perspective drawing of the packing arrangement of the title compound in the crystalline form.
La síntesis de un derivado diacetilénico de fórmula C26H44N2O4 se llevó a cabo por medio de una condensación de Glaser, y la caracterización estructural se realizó por difracción de rayos X en monocristal. El compuesto resultó dificil de cristalizar, y solamente un monocristal en forma de lámina con un espesor limitado a 40 m se obtuvo para medir datos. Al ser el poder de difracción débil, la resolución experimental se limitó a 0.91 A, y no fue posible obtener una esfera de difracción completa, debido a la descomposición de la muestra bajo irradiación, probablemente a consecuencia de una polimerización en el estado sólido. Tal comportamiento se había reportado anteriormente para otros derivados diacetilénicos cercanos. La molécula se ubica sobre un centro de inversión, con los sustituyentes n-octil en conformación extendida trans, generando un sistema molecular con una longitud mayor a 36 A. Los grupos uretano forman puentes de hidrógeno intermoleculares N-H ... O a lo largo del eje cristalográfico corto a. La estructura supramolecular resultante, basada en ciclos R22 (30), es bidimensional, y los planos supramoleculares se apilan a una corta distancia de 3.65 A, adecuada para la polimerización en el estado sólido.
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