Optimization of conventional hydroxamic acid for cassiterite flotation: Application of structural modification under principle of isomerism

2021 ◽  
Vol 167 ◽  
pp. 106901
Author(s):  
Yuxi Lu ◽  
Shuai Wang ◽  
Hong Zhong
Author(s):  
Pham V. Huong ◽  
Stéphanie Bouchet ◽  
Jean-Claude Launay

Microstructure of epitaxial layers of doped GaAs and its crystal growth dynamics on single crystal GaAs substrate were studied by Raman microspectroscopy with a Dilor OMARS instrument equipped with a 1024 photodiode multichannel detector and a ion-argon laser Spectra-Physics emitting at 514.5 nm.The spatial resolution of this technique, less than 1 μm2, allows the recording of Raman spectra at several spots in function of thickness, from the substrate to the outer deposit, including areas around the interface (Fig.l).The high anisotropy of the LO and TO Raman bands is indicative of the orientation of the epitaxial layer as well as of the structural modification in the deposit and in the substrate at the interface.With Sn doped, the epitaxial layer also presents plasmon in Raman scattering. This fact is already very well known, but we additionally observed that its frequency increases with the thickness of the deposit. For a sample with electron density 1020 cm-3, the plasmon L+ appears at 930 and 790 cm-1 near the outer surface.


2017 ◽  
Author(s):  
Jeremy Roach ◽  
Yusuke Sasano ◽  
Cullen Schmid ◽  
Saheem Zaidi ◽  
Vsevolod Katritch ◽  
...  

Salvinorin A (SalA) is a plant metabolite that agonizes the human <i>kappa</i>-opioid receptor (κ-OR) with high affinity and high selectivity over <i>mu- </i>and <i>delta-</i>opioid receptors. Its therapeutic potential has stimulated extensive semi-synthetic studies and total synthesis campaigns. However, structural modification of SalA has been complicated by its instability, and efficient total synthesis has been frustrated by its dense, complex architecture. Treatment of strategic bonds in SalA as dynamic and dependent on structural perturbation enabled the identification of an efficient retrosynthetic pathway. Here we show that deletion of C20 simultaneously stabilizes the SalA skeleton, simplifies its synthesis and retains its high affinity and selectivity for the κ-OR. The resulting 10-step synthesis now opens the SalA scaffold to deep-seated property modification.


2019 ◽  
Vol 23 (5) ◽  
pp. 503-516 ◽  
Author(s):  
Qiang Zhang ◽  
Xude Wang ◽  
Liyan Lv ◽  
Guangyue Su ◽  
Yuqing Zhao

Dammarane-type ginsenosides are a class of tetracyclic triterpenoids with the same dammarane skeleton. These compounds have a wide range of pharmaceutical applications for neoplasms, diabetes mellitus and other metabolic syndromes, hyperlipidemia, cardiovascular and cerebrovascular diseases, aging, neurodegenerative disease, bone disease, liver disease, kidney disease, gastrointestinal disease and other conditions. In order to develop new antineoplastic drugs, it is necessary to improve the bioactivity, solubility and bioavailability, and illuminate the mechanism of action of these compounds. A large number of ginsenosides and their derivatives have been separated from certain herbs or synthesized, and tested in various experiments, such as anti-proliferation, induction of apoptosis, cell cycle arrest and cancer-involved signaling pathways. In this review, we have summarized the progress in structural modification, shed light on the structure-activity relationship (SAR), and offered insights into biosynthesis-structural association. This review is expected to provide a preliminary guide for the modification and synthesis of ginsenosides.


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