The present invention relates to an improved process for the manufacture of beta -(3-oxo-7 alpha -thioacyl-17 beta -hydroxy-4-androstene-17 alpha -yl)-propionic acid gamma -lactones in which a beta -(3-oxo-17 beta -hydroxy-4,6-androstadiene-17 gamma -yl)-propionaldehyde cyclohemiacetal alkyl glycoside is reacted with a thiocarboxylic acid in a mixture of water and an organic solvent miscible with water to yield a 3-(3'-oxo-7 alpha '-thioacyl-17 beta '-hydroxy-4'-androstene-17 alpha '-yl)-propionaldehyde cyclohemiacetal alkyl glycoside and in which the compound thus obtained is oxidized in an acid solution, the alkyl glycoside radical in the cyclohemiacetal group being split off, to yield the corresponding gamma -lactone; the invention further relates to new intermediates useful in this process and having the formula IN WHICH R1 stands for the methyl group or a hydrogen atom and R2 and R3 each for an alkyl group having 1 to 5 carbon atoms.
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