Synthesis of triterpene glycosides
Summary1. The acyl-β-D-glucopyranosides, acyl-β-D-xylopyranosides, and acyl-α-L-arabinopyranosides of oleanolic and ursolic acids have been synthesized for the first time.2. A method for the synthesis of acyl glycosides of triterpene hydroxyacids with hindered carboxy groups has been developed.
Preparation of Acetobrome-Sugars
THE preparation of acetobrome-sugars involves generally the use of hydrogen bromide dissolved in glacial acetic acid or acetic anhydride. These solutions are very disagreeable to handle and to prepare; we therefore tried to circumvent their use, and after some preliminary experiments found a really satisfactory way of doing so.
Effects of the mineral phase and valence of vanadium on vanadium extraction from stone coal
The influence of roasting on the leaching rate and valence of vanadium was evaluated during vanadium extraction from stone coal. Vanadium in stone coal is hard to be leached and the leaching rate is less than 10% when the raw ore is leached by 4 mol/L H2SO4 at 90°C for 2 h. After the sample is roasted at 900°C for 2 h, the leaching rate of vanadium reaches the maximum, and more than 70% of vanadium can be leached. The crystal of vanadium-bearing mica minerals decomposes and the content of V(V) increases with the rise of roasting temperature from 600 to 900°C, therefore the leaching rate of vanadium increases significantly with the decomposition of the mica minerals. Some new phases, anorthite for example, form when the roasting temperature reaches 1000°C. A part of vanadium may be enwrapped in the sintered materials and newly formed phases, which may impede the oxidation of low valent vanadium and make the leaching rate of vanadium drop dramatically. The leaching rate of vanadium is not only determined by the valence state of vanadium but also controlled by the decomposition of vanadium-bearing minerals and the existence state of vanadium to a large extent.