The invention relates to a new process for the synthesis of 17&bgr;-hydroxy-17&agr;-methyl-2-oxa-5&agr;-androstane-3-one of formula (I). The process according to the invention is as follows: the 17&bgr;-hydroxy-17&agr;-ethyl-1,3-seco-2-nor-5&agr;-androstane-1,3-diacid of formula (III) is transformed into the ring-closed 17&bgr;-hydroxy-17&agr;-methyl-1,3-seco-2-nor-5&agr;-androstane-1,3-diacid anhydride of formula (II) in an inert solvent or without solvent with a C2-C3 alkan acid anhydride or a substituted carbodiimide of formula R1—N═C═N—R2— wherein R1 and R2 independently are C1-C6 alkyl group, C1-C6 alkyl group substituted by tertiary or quaternary amino group or 1-3 phenyl group, C5-C6 cycloalkyl group, aryl group substituted by 1-3 methoxy, tertiary amino, nitro, C1-C4 alkyl group or 1-3 halogen atom—and the obtained compound of formula (II) is reduced regioselectively by a complex alkali metal hydride in an inert solvent The new 17&bgr;-hydroxy-17&agr;-methyl-1,3-seco-2-nor-5&agr;-androstane-1,3-diacid anhydride of formula (II) is also the subject of the invention.