Antigestagenically active steroids with a fluorinated 17-alpha-alkyl chain

A method for treating breast cancer or post-coital birth control comprising administering to a human in need thereof an effective amount of a 17α-Fluoroalkyl steroid of general formula I

• in which
• R1 stands for a methyl or ethyl group,
• R2 stands for a radical of formula CnFmHo, whereby n is 2, 3, 4, 5 or 6, m>1 and m+o=2n+1,
• R3 stands for a free etherified or esterified hydroxy group,
• R4 and R5 each stand for a hydrogen atom, together for an additional bond or a methylene group,
• St stands for a steroidal ABC-ring system of partial formula A, B or C
• in which
• R6 means a hydrogen atom, a straight-chain C1-C4 alkyl group or branched C3-C4 alkyl group or a halogen atom,
• R7 means a hydrogen atom, a straight-chain C1-C4 alkyl group or a branched C3-C4 alkyl group, or
• if St stands for a steroidal ABC-ring system A or B, in addition
• R6 and R7 together mean an additional bond,
• X means an oxygen atom, a hydroxyimino grouping=N—OH or two hydrogen atoms,
• R8 means a radical Y or an aryl radical that is optionally substituted in several places with a group Y, whereby Y is a hydrogen atom, a halogen atom, an —OH, —NO2, —N3, —CN, —NR9aR9b, —NHSO2R9, —CO2R9, C1-C10 alkyl, C1-C10 alkoxy, C1-C10 alkanoyloxy, benzoyloxy, C1-C10 alkanoyl, C1-C10 hydroxyalkyl or benzoyl group, and R9a and R9b are the same or different and represent a hydrogen atom or a C1-C10 alkyl group,
• or for a —NR9aR9b radical, also a physiologically compatible salt thereof with an acid, or for a —CO2R9 radical in which R9 is hydrogen, also a physiologically compatible salt thereof with a base.