| abstract |
This invention discloses a method of conversion of carboxylic acids to carbothiotic acids by reacting a caarbpxylic acid with a first base, an iodide 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. |