Process for the esterification of a carbothioic acid

PROCESS FOR THE GROUP ESTERITICAÇÃO hydroxyl at C-17 ACID 6a, 9a-difluoro-11B, 17a-dihydroxy-16a-methyl-3-oxoandrosta-1, 4-diene-17B-carbothioic acid, compound of formula [I] which comprises reacting the compound [I] with a slight excess of an acyl chloride FORMULA GENERAL R-COC1, in which R represents -CH2CH3, -CH2CH2CH3 or -CH (CH3) 2 in the presence of an amine tertiary IN iNERT SOLVENT, at a temperature of 5 ° C TO -20 ° C GETTING UP, sELECTIVE OF FORM, THE dERIVATIVE 17A-acyl FORMULA [II].