Meiosis regulating compounds

Abstract

Certain compounds, structurally related to natural compounds which can be extracted i.a. from bull testes and from human follicular fluid, can be used for regulating the meiosis in oocytes and in male germ cells. Some of these compounds are useful in the treatment of infertility, whereas other compounds are useful as contraceptives. These compounds have the structural formula wherein the substituents are as defined in the specification.

1 . A compound of formula Ia:  
       
         
           
           
               
               
           
         
       
       wherein R 1  and R 2 , which are different or identical provided that they are not both hydroxy, are hydrogen, halogen, hydroxy or branched or unbranched C 1 -C 6 alkyl which may be substituted by halogen, hydroxy or cyano, or wherein R 1  and R 2  together designate methylene or oxo or, together with the carbon atom to which they are bound, form a cyclopropane ring, a cyclopentane ring, ora cyclohexane ring; R 3  is hydrogen, methylene, hydroxy, methoxy, acetoxy, oxo, halogen, C 1 -C 4  alkandiyl (bound to the same carbon atom of the sterol skeleton) or ═NOR 26  wherein R 25  is hydrogen or C 1 -C 3  alkyl, or R 3  designates, together with R 9  or R 14 , an additional bond between the carbon atoms at which R 3  and R 9  or R 14  are placed; R 4  is hydrogen, methylene, hydroxy, methoxy, acetoxy, oxo, halogen, C 1 -C 4  alkandiyl (bound to the same carbon atom of the sterol skeleton) or ═NOR 27  wherein R 27  is hydrogen or C 1 -C 3  alkyl, or R 4  designates, together with R 13  or R 5 , an additional bond between the carbon atoms at which R 4  and R 13  or R 15  are placed; R 5  is hydrogen, halogen, C 1 -C 4  alkyl, methylene, hydroxy, methoxy, oxo or ═NOR 22  wherein R 22  is hydrogen or C 1 -C 3  alkyl, or R 5  designates, together with R 6  an additional bond between the carbon atoms at which R 5  and R 5  are placed; R 5  is hydrogen or hydroxy or R 6  designates, together with R 5 , an additional bond between the carbon atoms at which R 5  and R 6  are placed; R 9  is hydrogen, hydroxy, halogen or oxo or R 9  designates, together with R 3  or R 10 , an additional bond between the carbon atoms at which R 9  and R 3  or R 10  are placed; R 10  is hydrogen, halogen or hydroxy, or R 10  designates, together with R 9 , an additional bond between the carbon atoms at which R 10  and R 9  are placed; R 11  is hydroxy, optionally substituted alkoxy, acyloxy, sulphonyloxy, phosphonyloxy, oxo, halogen, C 1 -C 4  alkandiyl (bound to the same carbon atom of the sterol skeleton) or ═NOR 28  wherein R 28  is hydrogen or C 1 -C 3  alkyl, or R 11  designates, together with R 12 , an additional bond between the carbon atoms at which R 11  and R 12  are placed; R 12  is hydrogen, hydroxy, C 1 -C 3  alkyl, vinyl, C 1 -C 3  alkoxy or halogen, or R 12  designates, together with R 11 , an additional bond between the carbon atoms at which R 12  and R 11  are placed; R 13  is hydrogen, hydroxy or halogen or R 13  designates, together with R 4  or R 14 , an additional bond between the carbon atoms at which R 13  and R 4  or R 14  are placed; R 14  is hydrogen, hydroxy or halogen, or R 14  designates, together with R 3 , R 6  or R 13 , an additional bond between the carbon atoms at which R 14  and R 3  or R 6  or R 13  are placed; R 15  is hydrogen, halogen, C 1 -C 4  alkyl, methylene, hydroxy, methoxy, acetoxy, oxo or ═NOR 23  wherein R 23  is hydrogen or C 1 -C 3  alkyl, or R 15  designates, together with R 4 , an additional bond between the carbon atoms at which R 15  and R 4  are placed; R 16  is hydrogen, halogen, C 1 -C 3  alkyl, methylene, hydroxy, methoxy, oxo or ═NOR 24  wherein R 24  is hydrogen or C 1 -C 3  alkyl, or R 16  designates, together with R 17 , an additional bond between the carbon atoms at which R 16  and R 17  are placed; R 17  is hydrogen or hydroxy, or R 17  designates, together with R 16 , an additional bond between the carbon atoms at which R 17  and R 16  are placed; R 18  and R 19  are both hydrogen, or one of R 18  and R 19  is hydrogen while the other is halogen, hydroxy or methoxy, or R 18  and R 19  together designate oxo; R 25  is C 1 -C 4  alkyl or hydroxymethyl, or R 25  and R 31  together designate methylene or oxo; R 29  is hydrogen, halogen, methyl, hydroxy or oxo; R 30  is hydrogen, halogen, methyl or hydroxy; R 31  is hydrogen, halogen, methyl or hydroxy, or R 31 , together with R 25 , designates methylene or oxo; and A is a carbon atom or a nitrogen atom; and when A is a carbon atom, R 7  is hydrogen, hydroxy or halogen; and R 8  is hydrogen, halogen, hydroxy, C 1 -C 4  alkyl, methylene or oxo, or R 7  designates, together with R 8 , an additional bond between the carbon atoms at which R 7  and R 8  are placed; R 20  is C 1 -C 4  alkyl, trifluoromethyl and C 3 -C 6  cycloalkyl; R 21  is C 1 -C 4  alkyl, C 1 -C 4  hydroxyalkyl, C 1 -C 4  haloalkyl containing up to three halogen atoms, methoxymethyl, acetoxymethyl, and C 3 -C 6  cycloalkyl, or R 20  and R 2 ′, together with the carbon atom at which they are placed, form a C 3 -C 6  cycloalkyl ring; and when A is a nitrogen atom, R 7  designates a lone pair of electrons; and R 3  is hydrogen, hydroxy, C 1 -C 4  alkyl, cyano and oxo; and R 20  and R 21  are, independently, C 1 -C 4  alkyl or C 3 -C 6  cycloalkyl; provided that at least one of R 1 , R 2 , R 6 , R 8 , R 9 , R 10 , R 12 , R 13 , R 14 R 18 , R 19 , R 29 , R 30  and R 31  is hydroxy or R 25  is hydroxymethyl and further provided that R 9 , R 10  and R 11  are not all hydroxy and further provided that the compound is not 5α-bromocholestane-3β,6β-diol; 7α-bromocholestane-3β,6α-diol; 7α-bromocholestane-3β,6β-diol; 7α-bromocholestane-3β,5α-diol-6-one; 7β-bromocholestane-3β,5α-diol-6-one; 3β-bromocholestane-2α-ol; 5α-chlorocholestane-3β,6α-diol; 5α-chlorocholestane-3β,6β-diol; 6β-chlorocholestane-3β,5α-diol; Δ 7,9(11) -cholestadiene-3β,6α-diol; Δ 7,9(11) -cholestadiene-3β,6β-diol; cholestane-2α,3α-diol; cholestane-2α,3β-diol; cholestane-2β,3α-diol; cholestane-2β,3β-diol; cholestane-3α,4α-diol; cholestane-3α,4β-diol; cholestane-3β,4β-diol; cholestane-3α,5α-diol; cholestane-3β,5α-diol; cholestane-3β,6α-diol; cholestane-3β,6β-diol; cholestane-3β,22α-diol; cholestane-3β,22β-diol; cholestane-3β,7α,8α-triol; Δ 5 -cholestene-3β,4α-diol; Δ 5 -cholestene-3β,4β-diol; Δ 5 -cholestene-3β,20α-diol; Δ 5 -cholestene-3β,22α-diol; Δ 5 -cholestene-3β,22β-diol; Δ 5 -cholestene-3β,24α-diol; Δ 5 -cholestene-3β,24β-diol; Δ 6 -cholestene-3β,5α-diol; Δ 8(14) -cholestene-3β,9α-diol; Δ 11 -cholestene-3α,24-diol; Δ 5 -cholestene-3β,6-diol-7-one; Δ 6 -cholestene4α-ol-3-one; Δ 5 -cholestene-3β,4β,7α-triol; coprostane-3α,5β-diol; coprostane-3β,5β-diol; coprostane-3β,6β-diol; coprostane4β,5β-diol-3-one; 20β-hydroxy-20-iso-cholesterol; 4α-hydroxy-5α-cholestan-3-one; cholestan-3β,5α,6-triol-3β-hemisuccinate; cholestan-3β,5α,6β-triol-3β-hemisuccinate-6β-acetate; cholestan-3β,5α,6β-triol-3β-hemisuccinate-6β-formiate; cholestan-3β,5α,6β-triol-3β-sulphate; cholestan-3β,5α,6β-triol-3β-phosphate; 2β,3β,14α,22(R),25-pentahydroxycholest-7-en-6-one; cholest-7-en-2β,3β,5β,11α,14α,20(R),22(R)-heptahydroxy-6-one; 5,24-cholestadien-3β-ol; 5-cholesten-3β,24,25-triol-3α-acetate; 5-cholesten-3β,24,25-triol-3β,24-diacetate; 5,25-cholestadien-3α-ol acetate; 5-cholesten-3β,25,26-trol-3β-acetate; 5-cholesten-3β,25,26-trol; 24,25(or 25,26)-dihydroxycholecalciferol; cholest-5α-an-3β,6α-diol; cholest-5β-an-3β,6β-diol; cholest-5α-an-3,6-dione; cholest-5α-an-6β-ol-3-one; cholest-5α-an-2α-bromo-6β-ol-3-one; cholestan-3β,25-diol-3β-acetate; cholestan-3β,5α,25-triol-3β-acetate; cholestan-3β,5α,25-triol; cholestan-5α,25-diol-3-one; cholest-4-en-25-ol-3-one; cholesta-4,6-dien-25-ol-3-one; 1α,3α-dihydroxycholest-5-en; 1α,3β-dihydroxycholest-6-en; 3α,6α-dihydroxy-5β-cholestan-24-one; 3α,6α,24-trihydroxy-5β-cholestan; 3-chlorocholest-5,24-dien; 3α-hydroxycholest-5-en-24-on acetate; 3-chlorocholest-5-en-24-on; cholestan-25-fluoro-3β,22(S)-diol; cholestan-25-chloro-3β,22(S)-diol; cholestan-25-methyl-3β,22-diol; cholestan-25-methyl-3β,22-diol-3-hydrogenbutandioate; cholestan-25-methyl-3β,22-diol-bis-hydrogenbutandioate; 1α,25-dihydroxy-26,26,26,27,27,27-hexafluorocholes-5-en; 2β,3β,14α,22,25-pentahydroxy-Δ 7 -5β-cholesten-6-one; 25-hydroxy-3α-[(tetrahydro-2H-pyran-2-yl)oxy]cholest-5-en-24-on; 3β-[(tetrahydro-2H-pyran-2-yl)oxy]cholest-5-en-24-on; 25-hydroxy-24-oxocholesterol-3β-acetate; 24-oxocholesterol-3β-acetate; 25-hydroxy-24-oxocholesterol; 24,25-dihydroxycholesterol; 3α,6α,25-trihydroxy-24-oxo-5β-cholestane; 1α,25-dihydroxy-24-oxocholesterol; 1α,24,25-trihydroxycholesterol; 3α-hydroxy-24-oxocholesta-5,7-dien; 3β,25-dihydroxy-24-oxocholesta-5,7-dien; 3β-hydroxy-24-oxocholesta-5,7-dien; 1α,3β-dihydroxy-24-oxocholesta-5,7-dien; 1α,3β, 25-trihydroxy-24-oxocholesta-5,7-dien; (24R)-3β,24,25-trihydroxycholest-5-en; (24RS)-3β,24,25-trihydroxycholest-5-en; (24R)-1β,3β,24,25-tetrahydroxycholest-5-en; 4,4-dimethyl-24-methylene-3β-sulphooxy-12α-acetoxycholesta-8,14-dien-2α,11 β-diol; 4,4-dimethyl-24-methylene-3β-sulphooxy-12α-acetoxycholest-8-en-2α,11β-diol; 4,4-dimethyl-24-methylene-12α-acetoxycholesta-8,14-dien-2α,3β,11β-triol; 4,4-dimethyl-24-methylene-12α-acetoxycholesta-8,14-dien-3β,11β-diol; 4,4-dimethyl-24-methylene-12α-acetoxycholest-8-en-2α,3β,11-triol; 4,4-dimethyl-24-methylene-12α-acetoxycholest-8-en-3β,11β-diol; 4,4-dimethyl-24-methylenecholest-8-en-2,3β,11β,12α-tetraol; 4,4-dimethyl-24-methylene-3β-sulphooxycholesta-8,14-dien-2α,11β,12α-triol; 4,4-dimethyl-24-methylenecholesta-8,14-dien-2α,3β,11β,12α-tetraol; 4,4-dimethyl-24-methylene-3β-sulphooxy-12α-acetoxycholest-8-en-2-ol-11-one; mono(4,4-dimethyl-24-methylene-12α-acetoxycholesta-8,14-dien-2α,11β-diol)-3β-succinate; 1α,3β-dihydroxycholest-5-ene; 1α,3β,24-trihydroxycholest-5-ene; cholesta-5,7-diene-3β,23(R),25-triol; cholesta-5,7-diene-3β,23(S),25-triol; 1α,3β-dihydroxycholest-5-en; 1α,3,25-trihydroxycholest-5-en; Δ 7 -cholesten-2β,3β-diol-6-one; 2β,3β,14α,22(R),25-pentahydroxy-Δ 7 -5β-cholesten-6-one; 2β-3β,14α,22(S),25-pentahydroxy-Δ 7 -513-cholesten-6-one; cholest-5-en-3β,22(R,S),25-triol; cholest-5-en-25-fluoro-3β,22(R,S)-diol; cholest-5-en-25-fluoro-22(R,S)-ol-3β-semisuccinate; cholest-5-en-25-chloro-3β,22-diol; cholest-5-en-25-chloro-22-ol-3β-hemisuccinate; 3α,7α,12α,24,25-pentahydroxy coprostane; 3α,7α,12α,25-tetrahydroxy coprostane; 3α,7α,25-trihydroxy coprostane; 3α,7α,24,25-tetrahydroxy coprostane; 5β-cholestane-3α,7α,12α,24α,25-pentol; 5β-cholestane-3α,76α,12α,24β,25-pentol; 5β-cholestane-3α,7α,12α,25,26-pentol; 51-cholestane-3α,7α,12α,25-tetrol; 1α,2α,3β-trihydroxycholesta-5,7-diene; 1 α,2α-dihydroxy-31-acetoxycholesta-5-ene; cholest-5-en-2β-fluoro-1α,3β-diol; 24-cyclopropylchol-5-ene-3β,22(S)-diol-3-acatate; 24-cyclopropylchol-5-ene-3β,22(S)-diol; 24-cyclopropylchol-5-ene-3β,22(S)-diol 3 hydrogen butanedioate; 24-cyclopropyl-5α-cholane-3β,22(S)-diol; cholesta-1,4,6-trien-3-one; 1α,3β-dihydroxycholest-5-ene; 1α,3β-dihydroxy-5α-cholestane; 1α,3β-dihydroxycholesta-5,7-diene; 1β,3β-25-trihydroxycholest-5-ene; 1α,25-dihydroxycholesterol; 1α,25-dihydroxycholesterol-3-benzoate; cholest-5-en-3β,20(S)-diol; 2β,3β,14α,22(R),25-pentahydroxycholest-7-en-6-one; cholest-5-en-3β,22(S)-diol; cholest-5-en-3β,20(S)-diol; cholest-5-en-3β,22(S)-diol; cholest-5-en-3β,4β-diol; cholest-5-en-3β,22(R)-diol or 2β,3β,14α,22(R),25-pentahydroxycholest-7-en-6-one.  
     
     
         2 . A medicament comprising a compound of formula Ib  
       
         
           
           
               
               
           
         
       
       wherein R 1  and R 2 , which are different or identical provided that they are not both hydroxy, are hydrogen, halogen, hydroxy or branched or unbranched C 1 -C 6  alkyl which may be substituted by halogen, hydroxy or cyano, or wherein R 1  and R 2  together designate methylene or oxo or, together with the carbon atom to which they are bound, form a cyclopropane ring, a cyclopentane ring, or a cyclohexane ring; R 3  is hydrogen, methylene, hydroxy, methoxy, acetoxy, oxo, halogen, C 1 -C 4  alkandiyl (bound to the same carbon atom of the sterol skeleton) or ═NOR 26  wherein R 26  is hydrogen or C 1 -C 3  alkyl, or R 3  designates, together with R 9  or R 14 , an additional bond between the carbon atoms at which R 3  and R 9  or R 14  are placed; R 4  is hydrogen, methylene, hydroxy, methoxy, acetoxy, oxo, halogen, C 1 -C 4  alkandiyl (bound to the same carbon atom of the sterol skeleton) or ═NOR 27  wherein R 27  is hydrogen or C 1 -C 3  alkyl, or R 4  designates, together with R 13  or R 15 , an additional bond between the carbon atoms at which R 4  and R 13  or R 15  are placed; R 5  is hydrogen, halogen, C 1 -C 4  alkyl, methylene, hydroxy, methoxy, oxo or ═NOR 22  wherein R 22  is hydrogen or C 1 -C 3  alkyl, or R 5  designates, together with R 6  an additional bond between the carbon atoms at which R 5  and R 5  are placed; R 5  is hydrogen or hydroxy or R 6  designates, together with R 5 , an additional bond between the carbon atoms at which R 5  and R 6  are placed; R 9  is hydrogen, hydroxy, halogen or oxo or R 9  designates, together with R 3  or R 10 , an additional bond between the carbon atoms at which R 9  and R 3  or R 10  are placed; R 10  is hydrogen, halogen or hydroxy, or R 10  designates, together with R 9 , an additional bond between the carbon atoms at which R 10  and R 9  are placed; R 11  is hydroxy, optionally substituted alkoxy, acyloxy, sulphonyloxy, phosphonyloxy, oxo, halogen, C 1 -C 4  alkandiyl (bound to the same carbon atom of the sterol skeleton) or ═NOR 28  wherein R 28  is hydrogen or C 1 -C 3  alkyl, or R 11  designates, together with R 12 , an additional bond between the carbon atoms at which R 11  and R 12  are placed; R 12  is hydrogen, hydroxy, C 1 -C 3  alkyl, vinyl, C 1 -C 3  alkoxy and halogen, or R 12  designates, together with R 11 , an additional bond between the carbon atoms at which R 12  and R 11  are placed; R 13  is hydrogen, hydroxy or halogen or R 13  designates, together with R 4  or R 14 , an additional bond between the carbon atoms at which R 13  and R 4  or R 14  are placed; R 14  is hydrogen, hydroxy or halogen, or R 14  designates, together with R 3 , R 6  or R 13 , an additional bond between the carbon atoms at which R 14  and R 3  or R 6  or R 13  are placed; R 15  is hydrogen, halogen, C 1 -C 4  alkyl, methylene, hydroxy, methoxy, acetoxy, oxo or ═NOR 23  wherein R 23  is hydrogen or C 1 -C 3  alkyl, or R 15  designates, together with R 4 , an additional bond between the carbon atoms at which R 15  and R 4  are placed; R 16  is hydrogen, halogen, C 1 -C 3  alkyl, methylene, hydroxy, methoxy, oxo or ═NOR 24  wherein R 24  is hydrogen or C 1 -C 3  alkyl, or R 16  designates, together with R 17 , an additional bond between the carbon atoms at which R 16  and R 17  are placed; R 17  is hydrogen or hydroxy, or R 17  designates, together with R 16 , an additional bond between the carbon atoms at which R 17  and R 16  are placed; R 18  and R 19  are both hydrogen, or one of R 18  and R 19  is hydrogen while the other is halogen, hydroxy or methoxy, or R 18  and R 19  together designate oxo; R 25  is C 1 -C 4  alkyl and hydroxymethyl, or R 25  and R 31  together designate methylene or oxo; R 29  is hydrogen, halogen, methyl, hydroxy or oxo; R 30  is hydrogen, halogen, methyl or hydroxy; R 31  is hydrogen, halogen, methyl or hydroxy, or R 3 ′, together with R 25 , designates methylene or oxo; and A is a carbon atom or a nitrogen atom; and when A is a carbon atom, R 7  is hydrogen, hydroxy or halogen; and R 8  is hydrogen, halogen, hydroxy, C 1 -C 4  alkyl, methylene or oxo, or R 7  designates, together with R 8 , an additional bond between the carbon atoms at which R 7  and R 8  are placed; R 20  is C 1 -C 4  alkyl, trifluoromethyl or C 3 -C 6  cycloalkyl; R 21  is C 1 -C 4  alkyl, C 1 -C 4  hydroxyalkyl, C 1 -C 4  haloalkyl containing up to three halogen atoms, methoxymethyl, acetoxymethyl, or C 3 -C 6  cycloalkyl, or R 20  and R 21 , together with the carbon atom at which they are placed, form a C 3 -C 6  cycloalkyl ring; and when A is a nitrogen atom, R 7  designates a lone pair of electrons; and R 8  is hydrogen, hydroxy, C 1 -C 4  alkyl, cyano or oxo; and R 20  and R 21  are, independently, C 1 -C 4  alkyl or C 3 -C 6  cycloalkyl; provided that at least one of R 1 , R 2 , R 6 , R 8 , R 9 , R 10 , R 12 , R 13 , R 14 , R 18 , R 19 , R 29 , R 30  and R 31  is hydroxy or R 25  is hydroxymethyl, further provided that R 9 , R 10  and R 11  are not all hydroxy, and further provided that the compound is not cholestan-3β,5α,6β-triol-3β-hemisuccinate; cholestan-3β,5α,6β-triol-3β-hemisuccinate-6β-acetate; cholestan-3β,5α,6β-triol-3β-hemisuccinate-6β-formiate; cholestan-3β,5α,6β-triol-3β-sulphate; cholestan-3β,5α,6β-triol-3β-phosphate; cholestan-3β,25-diol-3β-acetate; cholestan-3β,5α,25-triol-3β-acetate; cholestan-30,5α,25-triol; cholestan-5α,25-diol-3-one; cholest-4-en-25-ol-3-one; cholesta-4,6-dien-25-ol-3-one; 1α,3α-dihydroxycholest-5-en; 1α,3β-dihydroxycholest-6-en; 3α,6α-dihydroxy-5β-cholestan-24-one; 3α,6α,24-trihydroxy-5β-cholestan; 3-chlorocholest-5,24-dien; 3β-hydroxycholest-5-en-24-on acetate; 3-chlorocholest-5-en-24-on; cholestan-25-fluoro-3β,22(S)-diol; cholestan-25-chloro-3β,22(S)-diol; cholestan-25-methyl-3β,22-diol; cholestan-25-methyl-3β,22-diol-3-hydrogenbutandioate; cholestan-25-methyl-3β,22-diol-bis-hydrogenbutandioate; 2β,3β,14α,22,25-pentahydroxy-Δ 7 -5β-cholesten-6-one; (24R)-3β,24,25-trihydroxycholest-5-en; (24RS)-3β,24,25-trihydroxycholest-5-en; (24R)-1β,3β,24,25-tetrahydroxycholest-5-en; 4,4-dimethyl-24-methylene-3α-sulphooxy-12α-acetoxycholesta-8,14-dien-2α,11 β-diol; 4,4-dimethyl-24-methylene-3α-sulphooxy-12α-acetoxycholest-8-en-2α,11β-diol; 4,4-dimethyl-24-methylene-12α-acetoxycholesta-8,14-dien-2α,3β,11β-triol; 4,4-dimethyl-24-methylene-12α-acetoxycholesta-8,14-dien-3β,11 β-diol; 4,4-dimethyl-24-methylene-12α-acetoxycholest-8-en-2α,3β,11 β-triol; 4,4-dimethyl-24-methylene-12β-acetoxycholest-8-en-3β,11-diol; 4,4-dimethyl-24-methylenecholest-8-en-2,3β,11β,12α-tetraol; 4,4-dimethyl-24-methylene-3β-sulphooxycholesta-8,14-dien-2α,11β,12α-triol; 4,4-dimethyl-24-methylenecholesta-8,14-dien-2α,3β,11β,12α-tetraol; 4,4-dimethyl-24-methylene-3β-sulphooxy-12α-acetoxycholest-8-en-2-ol-11-one; mono(4,4-dimethyl-24-methylene-12α-acetoxycholesta-8,14-dien-2α,11β-diol)-3β-succinate; cholesta-5,7-diene-3β,23(R),25-triol; cholesta-5,7-diene-3β,23(S),25-triol; 2β,3β,14×4α,22(R),25-pentahydroxy-Δ 7 -5β-cholesten-6-one; 2β,3β,14α,22(S),25-pentahydroxy-Δ 7 -5β-cholesten-6-one; cholest-5-en-3β,22(R,S),25-triol; cholest-5-en-25-fluoro-3β,22(R,S)-diol; cholest-5-en-25-fluoro-22(R,S)-ol-3β-semisuccinate; cholest-5-en-25-chloro-3β,22-diol; cholest-5-en-25-chloro-22-ol-3β-hemisuccinate; 3α,7α,12α,24,25-pentahydroxy coprostane; 3α,7α,12α,25-tetrahydroxy coprostane; 3α,7α,25-trihydroxy coprostane; 3α,7α,24,25-tetrahydroxy coprostane; 5β-cholestane-3α,7α,12α,24α,25-pentol; 5β-cholestane-3α,7α,12α,24β,25-pentol; 5β-cholestane-3α,7α,12α,25,26-pentol; 5β-cholestane-3α,7α,12α,25-tetrol; cholest-5-en-2β-fluoro-1α,3α-diol; 24-cyclopropylchol-5-ene-3β,22(S)-diol-3-acetate; 24-cyclopropylchol-5-ene-3β,22(S)-diol; 24-cyclopropylchol-5-ene-3β,22(S)-diol 3 hydrogen butanedioate; 24-cyclopropyl-5α-cholane-3β,22(S)-diol; cholesta-1,4,6-trien-3-one; 1α,3β-dihydroxycholest-5-ene; 1α,3β-dihydroxy-5α-cholestane; 1α,3β-dihydroxycholesta-5,7-diene; 1α,3β-25-trihydroxycholest-5-ene; 1α,25-dihydroxycholesterol or 1α,25-dihydroxycholesterol-3-benzoate.  
     
     
         3 . A compound of formula Ic:  
       
         
           
           
               
               
           
         
       
       wherein R 1  and R 2 , which are different or identical provided that they are not both hydroxy, are hydrogen, halogen, hydroxy or branched or unbranched C 1 -C 6  alkyl which may be substituted by halogen, hydroxy or cyano, or wherein R 1  and R 2  together designate methylene or oxo or, together with the carbon atom to which they are bound, form a cyclopropane ring, a cyclopentane ring, or a cyclohexane ring; R 3  is hydrogen, methylene, hydroxy, methoxy, acetoxy, oxo, halogen, C 1 -C 4  alkandiyl (bound to the same carbon atom of the sterol skeleton) or ═NOR 26  wherein R 25  is hydrogen or C 1 -C 3  alkyl, or R 3  designates, together with R 9  or R 14 , an additional bond between the carbon atoms at which R 3  and R 9  or R 14  are placed; R 4  is hydrogen, methylene, hydroxy, methoxy, acetoxy, oxo, halogen, C 1 -C 4  alkandiyl (bound to the same carbon atom of the sterol skeleton) or ═NOR 27  wherein R 27  is hydrogen or C 1 -C 3  alkyl, or R 4  designates, together with R 13  or R 15 , an additional bond between the carbon atoms at which R 4  and R 13  or R 15  are placed; R 5  is hydrogen, halogen, C 1 -C 4  alkyl, methylene, hydroxy, methoxy, oxo or ═NOR 22  wherein R 22  is hydrogen or C 1 -C 3  alkyl, or R 5  designates, together with R 6  an additional bond between the carbon atoms at which R 5  and R 6  are placed; R 6  is hydrogen or hydroxy or R 6  designates, together with R 5 , an additional bond between the carbon atoms at which R 5  and R 5  are placed; R 9  is hydrogen, hydroxy, halogen or oxo or R 9  designates, together with R 3  or R 10 , an additional bond between the carbon atoms at which R 9  and R 3  or R 11  are placed; R 10  is hydrogen, halogen or hydroxy, or R 10  designates, together with R 9 , an additional bond between the carbon atoms at which R 10  and R 9  are placed; R 11  is hydroxy, optionally substituted alkoxy, acyloxy, sulphonyloxy, phosphonyloxy, oxo, halogen, C 1 -C 4  alkandiyl (bound to the same carbon atom of the sterol skeleton) or ═NOR 28  wherein R 28  is hydrogen or C 1 -C 3  alkyl, or R” designates, together with R 12 , an additional bond between the carbon atoms at which R 11  and R 12  are placed; R 12  is hydrogen, hydroxy, C 1 -C 3  alkyl, vinyl, C 1 -C 3  alkoxy and halogen, or R 12  designates, together with R 11 , an additional bond between the carbon atoms at which R 12  and R 11  are placed; R 13  is hydrogen, hydroxy or halogen or R 13  designates, together with R 4  or R 4 , an additional bond between the carbon atoms at which R 13  and R 4  or R 14  are placed; R 14  is hydrogen, hydroxy or halogen, or R 14  designates, together with R 3 , R 6  or R 13 , an additional bond between the carbon atoms at which R 14  and R 3  or R 6  or R 13  are placed; R 15  is hydrogen, halogen, C 1 -C 4  alkyl, methylene, hydroxy, methoxy, acetoxy, oxo or ═NOR 23  wherein R 23  is hydrogen or C 1 -C 3  alkyl, or R 15  designates, together with R 4 , an additional bond between the carbon atoms at which R 15  and R 4  are placed; R 16  is hydrogen, halogen, C 1 -C 3  alkyl, methylene, hydroxy, methoxy, oxo or ═NOR 24  wherein R 24  is hydrogen or C 1 -C 3  alkyl, or R 16  designates, together with R 17 , an additional bond between the carbon atoms at which R 16  and R 17  are placed; R 17  is hydrogen or hydroxy, or R 17  designates, together with R 16 , an additional bond between the carbon atoms at which R 17  and R 16  are placed; R 18  and R 19  are both hydrogen, or one of R 18  and R 19  is hydrogen while the other is halogen, hydroxy or methoxy, or R 18  and R 19  together designate oxo; R 25  is C 1 -C 4  alkyl and hydroxymethyl, or R 25  and R 31  together designate methylene or oxo; R 29  is hydrogen, halogen, methyl, hydroxy or oxo; R 30  is hydrogen, halogen, methyl or hydroxy; R 31  is hydrogen, halogen, methyl or hydroxy, or R 3 ′, together with R 25 , designates methylene or oxo; and A is a carbon atom or a nitrogen atom; and when A is a carbon atom, R 7  is hydrogen, hydroxy and halogen; and R 3  is hydrogen, halogen, hydroxy, C 1 -C 4  alkyl, methylene and oxo, or R 7  designates, together with R 8 , an additional bond between the carbon atoms at which R 7  and R 3  are placed; R 20  is C 1 -C 4  alkyl, trifluoromethyl or C 3 -C 6  cycloalkyl; R 21  is C 1 -C 4  alkyl, C 1 -C 4  hydroxyalkyl, C 1 -C 4  haloalkyl containing up to three halogen atoms, methoxymethyl, acetoxymethyl, and C 3 -C 6  cycloalkyl, or R 20  and R 2 ′, together with the carbon atom at which they are placed, form a C 3 -C 6  cycloalkyl ring; and when A is a nitrogen atom, R 7  designates a lone pair of electrons; and R 8  is hydrogen, hydroxy, C 1 -C 4  alkyl, cyano or oxo; and R 20  and R 21  are, independently, C 1 -C 4  alkyl or C 3 -C 6  cycloalkyl; provided that at least one of R 2 , R 6 , R 8 , R 8 , R 9 , R 10 , R 11 , R 12 , R 13 R 18 , R 19 , R 29 , R 30  and R 31  is hydroxy or R 25  is hydroxymethyl, and further provided that R 9 , R 10  and R 11  are not all hydroxy, wherein the compound is useful for regulating meiosis in a mammalian germ cell.  
     
     
         4 . A method of regulating meiosis in a mammalian germ cell comprising administering to a germ cell in need thereof an effective amount of a compound of  claim 3 .  
     
     
         5 . The method of  claim 4  wherein the compound is administered to the germ cell by administering it to a mammal hosting the germ cell.  
     
     
         6 . The method according to  claim 4  wherein the germ cell is an oocyte.  
     
     
         7 . The method according to  claim 4  wherein the compound is administered to an oocyte ex vivo.  
     
     
         8 . The method according to  claim 4  wherein the germ cell is a male germ cell.  
     
     
         9 . The method according to  claim 4  whereby mature male germ cells are produced by administering a compound of  claim 3  to testicular tissue in vivo or in vitro.  
     
     
         10 . A pharmaceutical composition for regulating meiosis in a mammalian germ cell, the composition comprising as an active ingredient an effective amount of a compound of  claim 3  together with a pharmaceutically acceptable carrier.