Search results for " Synthesis"

Chiral Inversion of 1-Hydroxyethylpyrene Enantiomers Mediated by Enantioselective Sulfotransferases

1998

The benzylic alcohol 1-hydroxyethylpyrene (1-HEP) is activated to a mutagen by sulfotransferases. The sulfuric acid ester formed is difficult to detect, as it is rapidly hydrolysed back to the alcohol. Incubation of the individual enantiomers of 1-HEP with human hydroxysteroid sulfotransferase (hHST) or estrogen sulfotransferase (hEST), expressed in bacteria, led to the formation of the other enantiomer. The rates of sulfation were determined from the initial rates of chiral inversion of the alcohol, knowing that hydrolysis follows an SN1 mechanism and therefore produces racemic alcohol. hEST showed high enantioselectivity for S-1-HEP, whereas hHST strongly preferred the R-enantiomer. The r…

D-Glucose as a Pentavalent Chiral Scaffold

2003

A novel carbohydrate-based scaffold for combinatorial chemistry has been developed. This scaffold allows the selective attachment of five different side chains, giving rise to products of enormous structural diversity. As a demonstration of its usefulness, a series of model compounds has been prepared in high purity and yield by multistep parallel synthesis on a solid phase. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Combinatorial solid-phase synthesis using D-galactose as a chiral five-dimension-deversity scaffold

1999

Abstract All five hydroxy groups of galactose as the scaffold are used for selective coupling of side chains in a combinatorial methodology by application of a set of orthogonally stable protecting groups in combination with a thioglycoside anchor.

Using knowledge of human-generated code to bias the search in program synthesis with grammatical evolution

2021

Recent studies show that program synthesis with GE produces code that has different structure compared to human-generated code, e.g., loops and conditions are hardly used. In this article, we extract knowledge from human-generated code to guide evolutionary search. We use a large code-corpus that was mined from the open software repository service GitHub and measure software metrics and properties describing the code-base. We use this knowledge to guide the search by incorporating a new selection scheme. Our new selection scheme favors programs that are structurally similar to the programs in the GitHub code-base. We find noticeable evidence that software metrics can help in guiding evoluti…

Chemogenic versus biogenic synthesis of Selenium nanoparticles: a structural characterization

Among the plethora of available metal- and metalloid-based nanomaterials (NMs), selenium nanostructures (SeNSs) are one of the most interesting from an applicative perspective due to their intermediate properties between metals and non-metals, as well as their high biocompatibility. In this regard, the capability of microorganisms to biotransform toxic Se-oxyanions – i.e., selenite (SeO32-) and selenate (SeO42-) – into their less bioavailable elemental forms [Se(0)], mostly generating Se nanoparticles (SeNPs), represents as a useful and green alternative over chemogenic synthesis allowing to obtain highly thermodynamically stable NMs. However, their structural characterization, in terms of …

Chromium inhibition and size-selected Au nanocluster catalysis for the solution growth of low-density ZnO nanowires.

2015

The wet chemical synthesis of nanostructures has many crucial advantages over high-temperature methods, including simplicity, low-cost, and deposition on almost arbitrary substrates. Nevertheless, the density-controlled solution growth of nanowires still remains a challenge, especially at the low densities (e.g. 1 to 10 nanowires/100 μm(2)) required, as an example, for intracellular analyses. Here, we demonstrate the solution-growth of ZnO nanowires using a thin chromium film as a nucleation inhibitor and Au size-selected nanoclusters (SSNCs) as catalytic particles for which the density and, in contrast with previous reports, size can be accurately controlled. Our results also provide evide…

Optimal implementation of neural activation functions in programmable logic using fuzzy logic

2006

Abstract This work presents a methodology for implementing neural activation function in programmable logic using tools from fuzzy logic. This methodology will allow implementing these intrinsic non-linear functions using comparators and simple linear modellers, easily implemented in programmable logic. This work is particularized to the case of a hyperbolic tangent, the most common function in neural models, showing the excellent results yielded with the proposed approximation.

Synthesis and crystal structure of [(PhenH)(PhenH2)][BiCl6] . 2H2O with different o-phenanthroline protonations.

1998

The reaction between bismuthate oxide and phen (1,10-phenanthroline) in acid medium led to the isolation of the unusual [(PhenH)(PhenH2)][BiCl6] 2H2O derivative, which has been characterized by X-ray analysis and IR spectroscopy. The compound crystallizes in the triclinic space group P1 with a = 8.313(2), b = 9.349(2), c = 9.807(3) A, a = 86.39(3), B = 110.27(3) and y = 106.48(3)°. The crystal structure is made of [BiCl6] 3- anions and [(PhenHXPhenr2)]3+cations. A network of hydrogen bond interactions involving the two clathrated water molecules, the phenanthroline moiety and the chlorines characterizes the entire structure.

Fullerene-Polymers: Synthesis, Properties and Applications

2009

Written by an outstanding team of experts in the interdisciplinary areas of research, this book is based on a new classification of the different types of fullerene polymers according to their chemical structures. It covers all aspects, from different classes, to their synthesis and applications in material science. Of great interest to polymer and synthetic chemists, but also for material scientists and industrial chemists.

Catalytic Methods in Asymmetric Synthesis: Advanced Materials, Techniques, and Applications

2011