Search results for "D2"

Synthetic approaches towards huperzine A and B

2013

Huperzine A and B are potent acetylcholinesterase inhibitors and promising against Alzheimer's disease. Completed and formal total syntheses of these medically relevant alkaloids are presented and discussed.

Kinetics of photochemical isomerization of TFA-Gly-ZΔPhe into TFA-Gly-EΔPhe

2017

The kinetics of photoisomerization of trifluoroacetyl-(Z)-dehydrophenylalanylglycine into trifluoroacetyl-(E)- dehydrophenylalanylglycine was studied in the hope that light-induced reaction could be useful as a means of preparation of the E-dehydropeptides. The obtained results indicate that if this reaction carried out under irradiation with light of wavelength 360 nm it is practically irreversible and gave nearly quantitatively pure Eisomer Significantly, expected cyclic side-products were not observed in the reaction mixture, thus proving the preparative potential of the elaborated procedure.

Synthesis of 6,12-Disubstituted Methanodibenzo[b,f][1,5]dioxocins : Pyrrolidine Catalyzed Self-Condensation of 2′-Hydroxyacetophenones

2019

The preparation of unprecedented 6,12-disubstituted methanodibenzo[b,f][1,5]dioxocins from pyrrolidine catalyzed self-condensation of 2′-hydroxyacetophenones is herein described. This method provides easy access to this highly bridged complex core, resulting in construction of two C–O and two C–C bonds, a methylene bridge and two quaternary centers in a single step. The intricate methanodibenzo[b,f][1,5]dioxocin compounds were obtained in up to moderate yields after optimization of the reaction conditions concerning solvent, reaction times and the use of additives. Several halide substituted methanodibenzo[b,f][1,5]dioxocins could be prepared from correspondent 2′-hydroxyacetophenones.

Photochemistry of triazolopyridinium ylides

2000

Glycosidopyrroles. Part 4. 1-β-D-ribofuranosyl-pyrroles and indoles as potential antiviral agents

2000

The preparation of new 1-β-D-ribofuranosylpyrroles of type 8 and a new method of synthesis of 1-β-D-ribofuranosylindoles of type 10, according to the scheme, is reported. All these new derivatives showed promising chemical and physical analogies with bioactive molecules but did not show any antiviral activity againstHIV1.

Triazolopyridines 21.1 The stereochemistry of 1-[1,2,3]triazolo[1,5-a] pyridin-7-yl-4-(2H-[1,2,3]triazol-4-yl)-1,3-butadienes and triazolo ring openi…

2002

The synthesis and NMR study of the geometry of 1-[1,2,3]triazolo[1,5-a]pyridin-7-yl-4-(2H[1,2,3]triazol-4-yl)-1,3-butadienes 1a, 1b, 5 and of new 1-(6-substituted-2-pyridyl)-4-(2H[1,2,3]triazol-4-yl)-1,3-butadienes 8-10 is reported. The stereochemistry of all butadienes studied is 1E, 3E except for compound 5 that is the 1Z, 3Z stereoisomer of 1a.

Flow Behavior of Chain and Star Polymers and Their Mixtures

2018

Star-shaped polymers show a continuous change of properties from flexible linear chains to soft colloids, as the number of arms is increased. To investigate the effect of macromolecular architecture on the flow properties, we employ computer simulations of single chain and star polymers as well as of their mixtures under Poiseuille flow. Hydrodynamic interactions are incorporated through the multi-particle collision dynamics (MPCD) technique, while a bead-spring model is used to describe the polymers. For the ultradilute systems at rest, the polymers are distributed uniformly in the slit channel, with a weak dependence on their number of arms. Once flow is applied, however, we find that the…

Bathymetry time series using high spatial resolution satellite images

2020

The use of the new generation of remote sensors, such as echo sounders and Global Navigation Satellite System (GNSS) receivers with differential correction installed in a drone, allows the acquisition of high-precision data in areas of shallow water, as in the case of the channel of the Encañizadas in the Mar Menor lagoon. This high precision information is the first step to develop the methodology to monitor the bathymetry of the Mar Menor channels. The use of high spatial resolution satellite images is the solution for monitoring many hydrological changes and it is the basis of the three-dimensional (3D) numerical models used to study transport over time, environmental variability, and wa…

A Self-Contained and Automated Method for Flood Hazard Maps Prediction in Urban Areas

2020

Water depths and velocities predicted inside urban areas during severe storms are traditionally the final result of a chain of hydrologic and hydraulic models. The use of a single model embedding all the components of the rainfall&ndash

Estimating Human Impacts on Soil Erosion Considering Different Hillslope Inclinations and Land Uses in the Coastal Region of Syria

2020

Soils in the coastal region of Syria (CRoS) are one of the most fragile components of natural ecosystems. However, they are adversely affected by water erosion processes after extreme land cover modifications such as wildfires or intensive agricultural activities. The main goal of this research was to clarify the dynamic interaction between erosion processes and different ecosystem components (inclination, land cover/land use, and rainy storms) along with the vulnerable territory of the CRoS. Experiments were carried out in five different locations using a total of 15 erosion plots. Soil loss and runoff were quantified in each experimental plot, considering different inclinations and land u…