Patent ID: 7868194

Claim:
A process for the preparation of 21(S)-hydroxy steroids with epimeric purity higher than 50%, having general formula (I) wherein R 1 is an alkyl group having from 1 to 3 carbon atoms, R 2 is an alkyl group having from 1 to 12 carbon atoms, R 3 is an alkyl group having from 1 to 4 carbon atoms, comprising the following steps i) reaction of 3,3-alkylendioxy-17β-(1-oxoalkyl)-5(10),9(11)-gonadiene of formula (II) with an oxaziridine in the presence of a strong organic base in an organic solvent, to give 3,3-alkylendioxy-17β-[(2S)-2-hydroxy-1-oxoalkyl]-5(10),9(11)-gonadiene of formula (III) wherein R 1 , R 2 and R 3 are defined as above, and n is an integer comprised from 2 to 4, ii) reaction of 3,3-alkylendioxy-17β-[(2S)-2-hydroxy-1-oxoalkyl]-5(10),9(11)-gonadiene of general formula (III) with a Cerium compound in an organic solvent, to obtain the desired 21(S)-hydroxy steroids of general formula (I) wherein R 1 , R 2 and R 3 are defined as above, and n is an integer comprised from 2 to 4.