An update of biocatalytic selective acylation and deacylation of monosaccharides

Partially acylated monosaccharides (PAMs) exhibit diverse and interesting applications but due to their polyhydroxylated nature, their synthesis requires regio- and stereoselective reactions. These features are provided by biocatalytic processes and in particular by hydrolases, which offer mild conditions and selective routes for the preparation of PAMs. Since this strategy has been extensively explored, the aim of the present review is to update research on enzymatic selective acylation and deacylation of monosaccharides, focusing on enzymatic preparation of synthetic useful PAMs and drug–monosaccharide conjugates involving PAMs.Fil: Iribarren, Adolfo Marcelo. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Área Química. Laboratorio de Biotransformaciones; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Iglesias, Luis Emilio. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Área Química. Laboratorio de Biotransformaciones; Argentin

The imaginary part of the high-harmonic cutoff

High-harmonic generation - the emission of high-frequency radiation by the ionization and subsequent recombination of an atomic electron driven by a strong laser field - is widely understood using a quasiclassical trajectory formalism, derived from a saddle-point approximation, where each saddle corresponds to a complex-valued trajectory whose recombination contributes to the harmonic emission. However, the classification of these saddle-points into individual quantum orbits remains a high-friction part of the formalism. Here we present a scheme to classify these trajectories, based on a natural identification of the (complex) time that corresponds to the harmonic cutoff. This identification also provides a natural complex value for the cutoff energy, whose imaginary part controls the strength of quantum-path interference between the quantum orbits that meet at the cutoff. Our construction gives an efficient method to evaluate the location and brightness of the cutoff for a wide class of driver waveforms by solving a single saddle-point equation. It also allows us to explore the intricate topologies of the Riemann surfaces formed by the quantum orbits induced by nontrivial waveforms.Comment: Supplementary Material is available at https://imaginary-harmonic-cutoff.github.io with a stable version at https://doi.org/10.5281/zenodo.369256

Algoritmos para encontrar anéis cromáticos em redes de parentesco

TCC(graduação) - Universidade Federal de Santa Catarina. Centro Tecnológico. Ciências da Computação.O trabalho tem como objetivo possibilitar a verificação de hipóteses sobre povos através da disponibilização de anéis cromáticos derivados de redes reais. Para isto, foi definido a utilização de grafos para representação das redes de parentesco reais. Um modo de colorir vértices deste grafo foi proposto com base em uma hipótese antropológica. Também foram propostos algoritmos que calculam propriedades derivadas das cores. Utilizando as propriedades obtidas, o trabalho desenvolveu formas de enumerar anéis cromáticos, implementando cada uma delas para execuções sequenciais e paralelas. Uma análise sobre o tempo de execução das buscas implementadas foi realizada sobre a rede real Arara. Uma análise numérica dos resultados também foi realizada sobre os 520 anéis com uma afinidade e 110590 anéis com duas afinidades encontrados para a rede.The goal of this work is to enable the verification of hypotheses about people by providing chromatic rings obtained from real networks. To achieve this goal, the use of graphs to represent real kinship networks was defined. A way of coloring vertices of this graph was proposed based on an anthropological hypothesis. Algorithms that calculate properties derived from colors have also been proposed. Using this properties, the work developed ways of enumerate all the chromatic rings, implementing each one to execute sequentially and parallelaly. An analysis of the execution time of the implemented searches was carried out on the Arara network, a real network. An analysis of numeric results was also performed on the 520 rings with one affinity and 110590 rings with two affinities found on the network

Candida antarctica B lipase-catalysed alcoholysis of peracetylated alkyl D-ribofuranosides

Candida antarctica B lipase (CAL-B) catalysed alcoholysis of a series of peracetylated alkyl α, β-D-ribofuranosides was assayed. Methyl and ethyl 2,3-di-O-acetyl-α, β-D-ribofuranosides enriched in the α-anomer were regioselectively prepared through this enzymatic deacetylation in 33% and 43% yield, respectively, the latter being a new compound. Isopropyl 2,3,5-tri-O-acetyl-β-D-ribofuranoside gave the new isopropyl 2,3-di-O-acetyl-β-D-ribofuranoside in 24% yield. The anomeric substituent affects the regioselectivity of the reaction, since n-propyl and n-butyl α, β-D-ribofuranosides reacted without selectivity.Fil: Gudiño, Esteban Dario. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Iribarren, Adolfo Marcelo. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres"; ArgentinaFil: Iglesias, Luis Emilio. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Regioselectivity of Lipase-Catalysed Deacetylation of Methyl 2,3,5-tri-OAcetyl-α, β-D-Furanosides in Ionic Liquid

Ionic liquids (ILs) were assayed as reaction medium for the enzymatic deacetylation of three methyl 2,3,5-tri-O-acetyl-a,b-D-furanosides and the obtained results show the influence of the IL and the furanose structure on the regioselectivity of hydrolyses catalysed by the tested lipases. In a reaction medium consisting of a 1:1 mixture of 30 mM phosphate buffer (pH 7) and 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]), Candida rugosa lipase catalysed the formation of methyl 2,3-di-O-acetyl-a,b-D-arabinofuranoside in 77 %, while in a 9:1 mixture of the same buffer and 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]), methyl 2,3-di-O-acetyl-a,b-D-ribofuranoside was obtained in 62 %.Fil: Gudino, Esteban D.. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Área Química. Laboratorio de Biotransformaciones; ArgentinaFil: Iribarren, Adolfo Marcelo. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Área Química. Laboratorio de Biotransformaciones; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Iglesias, Luis Emilio. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Área Química. Laboratorio de Biotransformaciones; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

An improved regioselective preparation of methyl 2,3-di-O-acetyl-α, β-d-xylofuranoside

Methyl 2,3-di-O-acetyl-α,β-d-xylofuranoside was prepared as the sole regioisomer in 6372% yield, according to the applied mass of substrate, through a Candida antarctica lipase B catalysed alcoholysis of methyl 2,3,5-tri-O-acetyl-α,β-d-xylofuranoside. The product is a potential synthetic precursor for 5-modified xylofuranosides and 5′-modified xylonucleosides.Fil: Gudiño, Esteban Dario. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Área Química. Laboratorio de Biotransformaciones; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Iribarren, Adolfo Marcelo. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Área Química. Laboratorio de Biotransformaciones; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres"; ArgentinaFil: Iglesias, Luis Emilio. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Área Química. Laboratorio de Biotransformaciones; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin