High purity 17α-cyanomethyl-17β-hydroxy-estra-4,9-diene-3-one and process for the synthesis thereof

Abstract

The invention relates to a new process for the synthesis of high purity 17α-cyanomethyl-17β-hydroxy-estra-4,9-diene-3-one (further on dienogest) of formula (I) from 3-methoxy-17-hydroxy-estra-2,5(10)-diene of formula (V). The invention relates also to the high purity 17α-cyanomethyl-17β-hydroxy-estra-4,9-diene-3-one and pharmaceutical compositions containing that as active ingredient. The pharmaceutical compositions according to this invention contain high purity dienogest of formula (I) in which the total amount of impurities is less than 0.1%, while the amount of 4-bromo-dienogest is under the detection limit (0.02%) as active ingredient or at least one of the active ingredients and auxiliary materials, which are commonly used in practice, such as carriers, excipients or diluents. According to our invention the dienogest of formula (I) is synthesized the following way: i) 3-methoxy-17-hydroxy-estra-2,5(10)-diene of formula (V) is reacted with aluminum isopropylate in the presence of cyclohexanone in an inert organic solvent under heating; ii) the so obtained 3-methoxy-estra-2,5(10)-diene-17-one of formula (IV) is reacted with cyanomethyl lithium at a temperature between 0 and −30° C.; iii) the obtained 3-methoxy-17α-cyanomethyl-17β-hydroxy-estra-2,5(10)-diene of formula (III) is reacted with a strong organic acid in tetrahydrofuran solution; iv) the obtained 17α-cyanomethyl-17β-hydroxy-estr-5(10)-ene-3-one of formula (II) is reacted with 1-1.5 equivalent of pyridinium tribromide in pyridine solution at a temperature between 0 and 60° C., then the obtained crude dienogest of formula (I) is purified by recrystallization and preparative HPLC.