METHOD FOR THE PREPARATION OF FLUTICASONE AND RELATED 17BETA-CARBOTHIOIC ESTERS USING A NOVEL CARBOTHIOIC ACID SYNTHESIS AND NOVEL PURIFICATION METHODS

摘要

This invention discloses a method of conversion of carboxylic acids to carbothiotic acids by reacting a caarbpxylic acid with a first base, an iodi de salt, and a compound of formula (4) wherein the variables are as defined in the claims, and reacting the product with a hydrolysing agent and then with an acid. The method is applied to the preparation of androstane carbothiolates, such as fluticasone propionate, which avoids column chromatography.