Known pregnane derivatives are prepared by esterificiation of known androstane derivatives to give new ester of Formula III ##STR1## wherein in each case symbolizes a single bond or a double bond, n is 1 or 2, R.sub.1 is hydrogen or methyl, R.sub.2 is hydrogen or formyl, and R.sub.3 is chlorine, hydroxy or an alkanoyloxy group of up to 6 carbon atoms, and reaction of the latter with Ag(I) and formic acid.