Conjugate additions of lithiated bislactim ethers derived from cyclo-[Gly-Val] and cyclo-[Ala-Val] to alpha-, beta-, or alpha,beta-substituted vinylphosphonates allow direct and stereoselective access to a variety of 3- or 4-monosubstituted and 2,3-, 2,4-, or 3,4-disubstituted 2-amino-4-phosphonobutanoic acids (AP4 derivatives) in enantiomerically pure form. The relative stereochemistry was assigned by X-ray diffraction analysis or NMR study of 1,2-oxaphosphorinane derivatives. Competitive eight-membered "compact" and "relaxed" transition-state structures are invoked to rationalize the stereochemical outcome of the conjugate additions.

Electrophilic substitutions on lithiated Schöllkopf's bis-lactim ethers derived from cyclo-[L-AP4-D-Val] take place regio- and stereoselectively at the alpha-position of the phosphonate ester. Subsequent olefination of alpha-silyl-, alpha-phosphoryl-, and alpha-stannyl-stabilized phosphonate carbanions give rise exclusively to vinylphosphonates. Both processes allow a direct and stereoselective access to a variety of 4-substituted and 3,4-disubstituted 2-amino-4-phosphonobutanoic acids (AP4 derivatives) in enantiomerically pure form that may be useful tools for characterizing the molecular pharmacology of metabotropic glutamate receptors (mGluRs) of group III. The relative stereochemistry was assigned from X-ray diffraction analyses or NMR studies of 1,2-oxaphosphorinane and other cyclic derivatives. In accordance to density functional theory (DFT) calculations, the syn-selectivity in the electrophilic substitutions may originate from the intervention of seven- and eight-membered chelate structures in which the bis-lactim ether moiety shields one of the faces of the phosphonate carbanion. DFT calculations for the tin-Peterson olefination of alpha-stannyl stabilized phosphonate carbanions indicate that rate and selectivity are determined in the initial carbon-carbon bond formation step where the unlike transition structures leading to (Z)-vinylphosphonates are favored both in the gas phase and in THF solution.

Face-selective conjugate addition of lithiated Schˆllkopf's bislactim ether derived from cyclo [Ala-D-Val] 4 to prochiral vinylphosphonates 5a-c allows a direct and stereocontrolled access to optically pure MAP4 analogues, the 2-amino-2methyl-4-phosphonobutanoic acid derivatives 12-15. The relative stereochemistry was assigned from NMR studies of the cyclic derivatives 16 and 17. Eight-membered transition states are invoked to rationalize the stereochemical outcome of the additions.

Rico-Díaz et al. | Un sistema de detección de peces para escala de hendidura vertical utilizando tecnología […] RESUMENLas escalas de hendidura vertical son una de las estructuras más utilizadas para sortear obstáculos como presas, centrales hidroeléctricas y otros. Conocer la frecuencia con la que los peces atraviesan este tipo de estructuras puede ayudar a conocer la eficacia de las mismas, así como a conocer características migratorias de las especies, determinar si el curso fluvial está sano o determinar si se puede pescar con garantías de conservación y mejora de la fauna. La técnica expuesta en este artículo es un método no invasivo para detección de peces en tiempo real, sin necesidad de observación directa. Se utiliza un sensor láser para detectar los peces y los datos recogidos por el sensor son analizados de forma automática con técnicas de visión artificial en una aplicación informática.Palabras clave | Visión Artificial; Escalas de Peces; Contador de peces; Detección por láser. ABSTRACT

Organo-phosphorus compounds Organo-phosphorus compounds S 0080Diastereoselective Synthesis of 2-Amino-4-phosphonobutanoic Acids by Conjugate Addition of Lithiated Schoellkopf's Bislactim Ethers to Vinylphosphonates.-The conjugate addition to vinylphosphonates takes place regio-and stereoselectively. 2,5-trans Isomers are formed with high predominance (one exception). The reaction with β-substituted vinylphosphonates proceeds with high 2,1' diastereoselectivity yielding 2,1'-anti or 2,1'-syn products depending on the configuration of the vinylphosphonates. Starting from α-substituted and α,β-disubstituted vinylphosphonates, different results are obtained. The nature of the α-substituent has a strong effect on the reaction outcome. In these cases, the selectivity can be improved by treatment of intermediates with bulky proton sources like 2,4,6-tri-tert-butylphenol. The resulting products can easily be transformed into 2-amino-4-phosphonobutanoic acids which are of interest for biological studies. -(RUIZ*, M.; FERNANDEZ, M. C.; DIAZ, A.; QUINTELA, J. M.; OJEA*, V.; J. Org. Chem. 68 (2003) 20, 7634-7645; Dep. Quim. Fundam. Ind., Fac. Cienc., Univ. La Coruna, E-15071 La Coruna, Spain; Eng.) -Jannicke 06-138 2004 Organo-phosphorus compounds