Potassium ethyl xanthate Potassium ethyl xanthate Potassium ethyl xanthate (KEX) is an organosulfur compound with the chemical formula CHCHOCSK. It is a pale yellow powder that is used in the mining industry for the separation of ores. Unlike the related sodium ethyl xanthate, the potassium salt exists as an anhydrous salt. Xanthate salts are prepared by the action of alkoxides on carbon disulfide. The alkoxide is often generated in situ from potassium hydroxide: Potassium ethyl xanthate is a pale yellow powder that is stable at high pH but rapidly hydrolyses at pH <9 at 25 °C. Unlike the sodium derivative, potassium xanthate crystallizes
Ethyl cyanohydroxyiminoacetate to HOAt without presenting an explosion risk such as the benzotriazoles. With water-soluble derivatives of ethyl cyanohydroxyiminoacetate (glyceroacetonide-oxyma) as additive and DIC as coupling reagent even in weakly basic aqueous solutions the linking of protected amino acids to oligopeptides is possible with a yield of 95% and a diastereomeric excess of> 99% using the model substances Z-"L"-Phg-OH and "L"-H-Pro-NH. In the coupling of amino acids, frequently occurring secondary reactions largely suppressed, which would be the formation of symmetrical acid anhydrides, racemization and epimerization and the cyclization to oxazolinones or - especially for dipeptides - to 2,5-diketopiperazines. Ethyl cyanohydroxyiminoacetate Ethyl cyanohydroxyiminoacetate