NO174393B - Analogous Procedures for Preparing Therapeutically Active 6-Methyl-19-nor-pregna-4,6-dienes which are 17 alpha-alkylated and optionally 21-alkylated - Google Patents

Description

This invention relates to the production of therapeutically active 6-methyl-19-nor-pregna-4,6-dienes which are 17a-alkylated and optionally 21-alkylated, and which have the formula I:

where R' and R" are the same or different and are hydrogen or a straight-chain or branched alkyl group with 1-3 carbon atoms,

and Rx is a straight or branched lower alkyl group of 1-6 carbon atoms.

In formula I, the group is

preferably 1-oxo-ethyl (ie R'=CH3 and R"=H), 1-oxo-propyl (R'=CH3 R"=H), 1-oxobutyl (R'=C2H5 and R"=H) , 1-oxo-2-methyl-propyl (R'=CH3 and R"=CH3) or 1-oxo-2-ethylbutyl (R'=CH2CH3 and R"=CH2CH3).

In formula I, R' and R" are preferably a methyl, ethyl or isopropyl group.

Some derivatives of 19-nor-progesterone are already known, especially those characterized by having 6-methyl-dienone on rings A and B in the steroid structure (see French patent document no. 2,271,833), such as e.g. 6-methyl-17α-hydroxy-3,20-dioxo-19-nor-pregna-4,6-diene and its esters and ethers. Several steroid derivatives which have the carbon skeleton of the 19-nor-progesterone, and which have an alkyl group on the 17- and/or 21-carbon, are known progestative agents (see French patent document no. 2,077,877), such as . 3,20-dioxo-17α-methyl-19-nor-pregna-4,9-diene.

The new compounds with the formula I show very interesting progestomimetic properties, an improved binding to the progesterone receptors and a reduced metabolism in the liver.

The effects of these new compounds can be attributed to a structure derived from 19-nor-progesterone, which is characterized by a steroid structure that simultaneously has the group designated "6-methyl-dienone group" and three substituents R', R" and Rx as indicated above, which structure means that the metabolism of the derivative is inhibited or reduced, without this preventing binding to the progesterone receptors.

Among the compounds of formula I should be mentioned: 6,17a,21-trimethyl-3,20-dioxo-19-nor-pregna-4,6-diene, 17a-ethyl-6,21-dimethyl-3,20-dioxo- 19-nor-pregna-4,6-diene, 17a-ethyl-6-methyl-3,20-dioxo-19-nor-pregna-4,6-diene, 6,17a-dimethyl-3,20-dioxo- 19-nor-pregna-4,6-diene and 17a,21-diethyl-6-methyl-3,20-dioxo-19-nor-pregna-4,6-diene,

which are the currently preferred compounds.

The new therapeutically active 17a-alkylated and optionally 21-alkylated 6-methyl-19-nor-pregna-4,6-dienes are produced by an analogous method which is characterized by the fact that a 3-oxo-19-nor-pregna-4-ene derivative with formula IV:

where R' and R" and Rx are as indicated above, subject to an enol etherification in acidic medium to form an enol ether of formula

W:

where R' and R" and Rx are as indicated above, and R2 is a lower alkyl radical, which compound is heated with a formylating agent of the Vilsmeier-Hack type to form a 6-formylated derivative of formula VI:

where R' and R", Rx and R2 are as indicated above,

this compound is reduced with a mixed alkali metal hydride to form a hydroxymethylated derivative of formula

VII:

where R', R", Ri and R2 are as indicated above,

this compound is treated with a mineral acid or organic acid to form a 3-oxo-6-methylene derivative of the formula

VIII:

where R', R" and Rx are as indicated above,

and this compound is inverted with an isomerization catalyst to form the corresponding 6-methylated derivative of formula I.

The starting materials of formula IV:

where R', R" and Rx have the meanings given above,

which are applicable in carrying out the analog method according to the invention, are suitably prepared according to the literature in that a 19-nor-steroid derivative of formula II:

where Ac is the acyl residue of a carboxylic acid with 1-4 carbon atoms, the wavy line indicates a- or (3-space configuration, and the ring A is either purely aromatic and of 3-alkoxy-1,3,5(10)-estratriene structure or is partially unsaturated and of 3-oxo-A-4-ester structure, and which is possibly blocked in the form of a functional derivative, with or without displacement of the double bond, is exposed to the action of a strong base and then of an alkylating agent to form a mono- or bis-alkylated derivative of the partial formula III:

where R', R" and Rx have the meanings given above.

The strong base is an alkali metal alkanolate derived from a straight-chain or branched lower alkanol with 1-5 carbon atoms and from a metal, such as lithium, sodium or potassium. Examples of such alkanolates are sodium tert-amylate, potassium tert-butylate and sodium ethanolate. The strong base can also be made up of an alkali metal or alkaline earth metal amide, such as e.g. an amide of lithium, sodium, potassium, calcium or barium. Sodium amide or lithium isopropyl amide is preferably used. Dimacyl sodium can also be used.

The alkylating agent can be a dialkyl sulphate, which e.g. dimethyl sulfate, or an alkyl halide, where the halogen is iodine or bromine.

The solvent can consist of a single solvent or a mixture of solvents selected from liquid ammonia, ether, tetrahydrofuran, benzene, toluene, hexane and ethanol. The preferred solvents are liquid ammonia and tetrahydrofuran.

The strong base and the alkylating agent are used in excess of the stoichiometric amount. The reaction is followed by an acid hydrolysis.

The compounds of the general formula III, which are mono- or poly-alkylated, are, if necessary, purified using suitable methods, such as e.g. crystallization or chromatography on a column filled with an absorbent suitable for chromatography, such as e.g. silica, talc, magnesium silicate or aluminum oxide.

The reaction temperature can vary within a wide temperature range, namely between -60°C and +50°C. Preferably it is between -60°C and -40°C, due to the preferred use

of ammonia as solvent.

For the preparation of a monoalkylated derivative (where R' and R" are hydrogen), it is preferred to use a lower concentration of basic agent (from 4 to 7 equivalents) and a lower concentration of the alkylating agent.

In contrast, when preparing a dialkylated derivative, it is necessary to introduce a larger amount of base agent (from 10 to 50 equivalents) and a larger amount of the alkylating agent (from 50 to 75 equivalents).

The choice of base is not entirely without importance. Experiments have shown that lithium isopropylamide is the best reagent for alkylation in the 21-position. The alkali metal alkanolates favor alkylation in the 17-position, and the preferred basic reagent in this case is the metal amide obtained by in situ reaction of liquid ammonia with an alkali metal or alkaline earth metal such as lithium or calcium.

The alkylation in the 17a position, where it is started with an alkali metal enolate, is a difficult reaction which necessitates the use of a very large excess of the basic reagent.

Access for the alkylating agent to the methyl group in the 21 position is much more difficult when the 17 position is already occupied by an alkyl group. A mixture of mono- and dialkylated derivatives in the 21-position must be prepared, and consequently the reaction requires a large excess of metal and alkylating agent. Monoalkylation in the 21-position is favored when a basic reagent such as e.g. lithium isopropylamide in tetrahydrofuran, due to the steric hindrance that this basic reagent entails.

In contrast, it is possible - by taking into account differences in the rate of alkylation - to alkylate first in the 17a position, introducing a small excess of the alkylating agent into the reaction mixture, and then add a new amount of alkylating agent, which may be the same or a other alkylating agent, to effect alkylation in the 21-position with an alkyl radical, which is the same as or different from that in the 17a-position.

It may also be possible to use as starting material a 19-nor-pregna-diene which has already been methylated in the 21-position and to carry out a dialkylation in the 17- and 21-positions, but in this case the alkylation in the 21- position is favoured, because the carbon atom in the 21 position forms a secondary carbanion which is more stable and is also more reactive.

' This reaction can be represented as follows for a

ethylation reaction.

<>> When an estratriene derivative of formula III is used as starting material, i.e. a compound in which the A ring is completely aromatic, the transfer to a compound of formula IV can be carried out using the following steps:

> A compound of formula III:

> where the substituents R', R", Rx and R2 are as indicated above,

is reduced according to Birch-Nielsen's method, after which hydrolysis is carried out in a strongly acidic medium and then a re-oxidation using Jones' reagent to form the 3-keto-19-nor-pregna-4-ene of formula IV.

The reduction according to Birch-Nielsen is carried out in an inert solvent, such as e.g. a cyclic ether or a linear ether, using an alkali metal dissolved in liquid ammonia and in the presence of a compound which is a proton donor, such as an alkanol, e.g. methanol or ethanol. Ammonia is then removed, and the excess of alkali metal eliminated by the addition of an alkanol. The resulting enol ether is then hydrolysed by the action of a strong mineral acid.

The new compounds of formula I can be used as active ingredients in the pharmaceutical preparations, alone or in admixture with one or more inert, non-toxic, pharmaceutically acceptable carriers.

The pharmaceutical preparations are intended to be administered parenterally, orally, rectally, through mucous membranes or through the skin.

For parenteral administration, the compounds of formula I are given in the form of injectable solutions or suspensions packaged in ampoules, multi-dose vials or automatic syringes.

For oral administration, the compounds of formula I can be given in the form of uncoated or coated tablets, dragees, soft gelatin capsules, hard capsules, pills, powders or granules.

For rectal administration, the compounds of formula I can be given in the form of suppositories or capsules for introduction into the rectum.

For administration via mucous membranes, the compounds of formula I are given in the form of oil solutions, creams, gels or capsules. It is possible to administer the compounds of formula I through the vaginal mucosa, the nasal mucosa or the ocular mucosa in the form of a spray or a gel.

For administration of the compounds of formula I through the skin, the compounds are given in the form of solutions or creams in a penetrating solvent, such as e.g. benzyl alcohol, dimethyl sulfoxide, 1-n-dodecyl-azacycloheptan-2-one ("Azone") or N-(p-hydroxyethyl)-acetamide.

The pharmaceutical preparations containing the new compounds are used in therapy for the treatment of gynecological disorders caused by insufficiency of the corpus luteum, such as e.g. irregularities in the menstrual flow, dysmenorrhea, premenstrual syndrome and disorders associated with menopause.

The doses usually vary from 0.05 to 25 mg per unit dose, and the daily dose ranges from 0.1 to 50 mg, by continuous administration or intermittent administration to women and female mammals.

The examples below illustrate the production of the new compounds.

Example 1 6,17a-dimethyl-3,20-dioxo-19-nor-preqna-4,6-diene.

Step A; 17a- acetoxv- 3- ethoxv- 20- oxo- 19- nor- preqna- 3, 5- diene.

To a solution of 126 g of 3,20-dioxo-17a-acetoxy-19-nor-pregna-4-ene in 1010 ml of ethanol, 115 g of ethyl orthoformate is added under an inert atmosphere and at room temperature, and after stirring for 10 minutes, 0.63 g is added p-toluenesulfonic acid.

The mixture is stirred for 60 minutes. The reaction is stopped by adding 17 ml of triethylamine. The medium is diluted with 380 ml of ethanol, and the mixture is refluxed until everything is dissolved.

Crystallization is achieved by allowing the solution to return to room temperature and then cooling using a bath of ice and acetone. 113 g of 3-ethoxy-17a-acetoxy-20-oxo-19-nor-pregna-3,5-diene are thereby obtained, which corresponds to a yield of 83% compared to the theoretical.

This enolet exhibits the following characteristics.

IR spectrum:

1740 cm-<1> (CO in acetoxy)

1710 cm"<1> (CO in 20)

1650, 1620 cm'<1> (delta-3.5)

UV spectrum: X max 243 nm, 6 = 20840

NMR spectrum: (T,3H) at 1.3 ppm CH3 (ethoxy)

(Q,2H) at 3.60 ppm CH2 (ethyl)

(S,1H) at 5.25 ppm H on C6

(S,1H) at 5.40 ppm H on C4.

Step B: 17a-methyl-3,20-dioxo-19-nor-preqna-4-ene and 17a-,21-dimethyl-3,20-dioxo-19-nor-preqna-4-ene.

A solution of 46 g of metallic calcium in 1000 ml of liquid ammonia cooled to -60°C is prepared in advance under an inert atmosphere. 30 g of the enol ether from step A is added dropwise to this solution in 495 ml of tetrahydrofuran. After stirring for 15 minutes, 363 ml of methyl iodide are added in portions. A gray-white blur appears. After the addition is complete, the mixture is stirred for 60 minutes, after which the ammonia is evaporated as completely as possible under vacuum, using a hot water bath. It is then added to 1000 ml of methanol and a 6N solution of hydrochloric acid, until an acidic pH is achieved, while the temperature is kept at 0°C by decomposing the mixture in a bath of acetone and ice. The mixture is then stirred for a further 60 minutes. The reaction products are precipitated by adding 2000 ml of water, after which they are extracted with toluene. After evaporation of the solvent, 22.9 g of an impure, oily product containing 68% of the 17a-methylated derivative and 24% of the 17a, 21-dimethylated derivative, determined by HPLC, are recovered.

Using column chromatography on silica, with elution with cyclohexane/ether (90:10), 1.1 g of the 17a-21-dimethylated derivative is isolated in the first fractions and then 6 g of the 17a-methylated derivative in the last fractions.

The two compounds are recrystallized separately from methanol. They show the following data:

-» 3, 20-dioxo-17a-methyl-19-nor-pregna-4-ene

IR spectrum: 1705 cm-<1> (CO in 20)

1680 cm"<1> (CO in 3)

1620 cm-<1> for the conjugated C=C

UV spectrum: k max 240 nm, 6 = 17385

NMR spectrum: (S,3H) at 1.2 ppm (CH3-17a)

(S,3H) at 2.2 ppm (CH3-21)

3,20-dioxo-17a, 21-dimethyl-19-nor-pregna-4-ene IR spectrum: 1697 cm-<1> (CO in 20)

1670 cm'<1> (CO in 3)

UV spectrum: k max 240 nm, € = 16515

NMR spectrum: (S,3H) at 1.2 ppm (CH3-17a)

(T,3H) at 1.07 ppm (CH3-22)

Multiplet at 2.55 ppm (CH2-21)

Step C: 3-ethoxy-17α-methyl-20-oxo-19-nor-preqna-3,5-diene.

This compound is prepared according to the method according to step A, starting with 3,20-dioxo-17a-methyl-19-nor-pregna-4-ene, and using 12 ml of ethanol, 1.85 ml of ethyl orthoformate, 0.102 g of p- toluenesulfonic acid and then 0.2 ml of triethylamine.

The crystalline enolet is obtained in a yield of 78% and exhibits the following spectral data:

IR spectrum: 1695 cm-<1> (CO in 20)

1640, 1620 cm"<1> (delta-3.5)

UV spectrum: X max 243 nm, E = 16520

NMR spectrum: (S,3H) at 1.15 ppm (CH3-17a)

(T,3H) at 1.30 ppm (CH3 in the ethoxy group)

(S,3H) at 2.15 ppm (CH3-21)

(Q,2H) at 3.80 ppm (CH2 in the ethoxy group)

(S,1H) at 5.22 ppm (H in C6)

(S,1H) at 5.32 ppm (H in C4)

Step D: 3- ethoxy- 6- formvl- 17a- methyl- 20- oxo- 19- norpreqna-3, 5- diene.

A formylation reagent is prepared by dissolving in portions and under a nitrogen atmosphere, at +2°C, 3.15 ml of freshly distilled POCl3 in 28 ml of dimethylformamide, with subsequent stirring for 5 minutes. The thus prepared reagent is dripped into a solution of 7 g of 3-ethoxy-17a-methyl-20-oxo-19-nor-pregna-3,5-diene in 56 ml of dimethylformamide over a period of 10-15 minutes. The mixture is stirred for 10 minutes, after which the resulting imonium ion is hydrolysed by careful addition of a solution of 14 g of potassium acetate in 28 ml of water, without allowing the temperature to exceed +30°C. The solution, which is initially red, changes color and becomes yellow as incipient crystallization takes place. After stirring for 30 minutes, 105 ml of ice water is added. An impure 3-ethoxy-6-formyl-17a-methyl-20-oxo-19-nor-pregna-3,5-diene is isolated in an amount of 7.2 g, corresponding to 95% of the theoretical amount. The impure product is crystallized from ethanol, whereby 3.1 g of pure compound with the following spectral data is obtained:

IR spectrum: 1700 cm-<1> (CO in 20)

1650 and 1615 (delta-3.5)

UV spectrum: X max 220 and 320 nm

NMR spectrum: Disappearance of the singlet (1H) at 5.22 ppm.

Step E: 17a-methyl-6-methylene-3,20-dioxo-19-nor-pregna-4-ene.

95 mg of sodium borohydride is added in small portions and under a nitrogen atmosphere at room temperature to a solution of 1.9 g of 3-ethoxy-17a-methyl-6-formyl-20-oxo-19-nor-pregna-3,5-diene in 5 .7 ml of ethanol and 4.7 ml of dimethylformamide. The mixture is stirred for 2 hours. The temperature of the reaction mixture is allowed to return to 0°C and a solution prepared from 0.4 ml of 2N sulfuric acid and 2 ml of water is added over a period of 2 minutes. The reaction temperature increases to 10°C, and a faint yellow smear appears as a gum. The mixture is stirred for a further 20 minutes. A solution of 0.88 g of potassium carbonate in 2 ml of water is then added dropwise. Thereby, the amount of sweep increases further. The skimming is filtered off and washed with copious amounts of water, until the wash water shows a neutral reaction. 1.40 g of 3,20-dioxo-6-methylene-17a-methyl-19-nor-pregna-4-ene are thereby obtained, corresponding to a yield of 87%.

IR spectrum: 1700 cm-<1> (CO in 20)

1660 cm-<1> (CO in 3)

1620, 1595 cm'<1> (C=C) .

UV spectrum: X max 263 nm 6 = 12280

NMR spectrum: Two incompletely resolved singlets appear at 5 ppm and 5.25 ppm.

Step F: 3,20-dioxo-6,17a-dimethyl-19-nor-preqna-4,6-diene (compound of formula I).

A suspension of 0.65 g of 5% palladium on carbon in 33.5 ml of methanol is prepared and refluxed for 30 minutes. To this suspension is added 1.34 g of the 6-methylene derivative from step E. The reaction is monitored by determining the extinction values in the ultraviolet range. After stirring for 30 minutes, the temperature of the mixture is allowed to return to room temperature. The mixture is then filtered through clay ("Clarcel"). The filtrate is separated, concentrated and chromatographed on silica in an amount corresponding to 30 times its weight, eluting with toluene. The fractions containing the 6-methylated derivative are recrystallized from methanol. 3,20-dioxo-6,17a-dimethyl-19-nor-pregna-4,6-diene is thereby obtained in an amount of 0.83 g, corresponding to 63% of the theoretical amount.

The analysis data is as follows:

IR spectrum: 1695 cm-<1> (CO in 20)

1650 cm"<1> (CO in 3)

1622, 1576 cm"<1> (delta-4.6)

UV spectrum: X max 289 nm € = 23900

Mass: 326 molar ion

283 loss of CH3C0

43 CH 3 CO

Drainability: [a]D: (dioxane) + 22°32

Sm.p. = 164.6°C

Elemental analysis: C22H30O2

NMR spectrum: (S,3H) at 0.76 ppm (CH3-18)

(S,3H) at 1.9 ppm (CH3-17a)

(S,3H) at 1.88 ppm (CH3 in 6)

(S,3H) at 2.16 ppm (CH3-21)

(S,1H) at 6.01 ppm (H in C7)

(S,1H) at 6.12 ppm (H in C4)

Example 2 6,17a-21-trimethyl-3,20-dioxo-19-norpreqna-4,6-diene

Step A: 3-ethoxy-17α-21-dimethyl-20-oxo-19-nor-preqna-3,5-diene.

Proceed as described in step A of example 1, starting with 5.85 g of 3,20-dioxo-17a,21-dimethyl-19-nor-pregna-4-ene prepared in step B of example 1, dissolved in 12 ml of ethanol, 5.9 ml of ethyl orthoformate and 0.029 g of p-toluenesulfonic acid. As soon as the reaction is complete, it is stopped by the addition of 0.6 ml of triethylamine.

The enol ether thus obtained does not crystallize and is extracted with benzene. The benzene vessels are washed with water, and the solvent is evaporated. 7.07 g of the enol ether are recovered, which after purification by chromatography on a column filled with basic aluminum oxide, eluting with hexane/triethylamine (99:1) gives 5.8 g of 3-ethoxy-17a,21-dimethyl- 20-oxo-19-nor-pregna-3,5-diene, which corresponds to a yield of 91%.

Step B: 3-ethoxy-6-formyl-17a,21-dimethyl-20-oxo-19-nor-preqna-3,5-diene.

Formylation of the compound from step A in the 6-position is carried out according to the procedure described in step D in example 1. It starts with 5.1 g of enol ether from step A dissolved in 41 ml of dimethylformamide.

The formylation reagent consists of 2.15 ml of POCl3 in 20 ml of dimethylformamide. The hydrolysis reagent consists of 13.8 g of potassium acetate in 20 ml of water.

4.4 g of impure 6-formylated derivative is thereby obtained, which corresponds to a yield of 77%.

Step C:

Using the same procedure as that described in step E in example 1 and by starting with 4.3 g of the 6-formylated derivative from step B dissolved in 43 ml of ethanol, reduction is carried out with a solution of 0.273 g of sodium borohydride in 4 ml of dimethylformamide. Stirring is continued for 10 minutes, after which the formed hydroxymethylated derivative is dehydrated with 5.15 ml of a 2N solution of sulfuric acid in 40 ml of water. 1.9 g of impure 6-methylene derivative is thereby obtained, which corresponds to a

dividend of 50%.

A = 258 nm.

Step D: 6,17a,21-trimethyl-3,20-dioxo-19-norpreqna-4,6-diene (compound of formula I).

A suspension of 0.14 g of palladium-on-charcoal in 25 ml of ethanol is refluxed for 60 minutes. 1.1 g of the 6-methylene derivative from step C is then added. The course of the reaction is followed by UV spectrophotometry. After stirring for 50 minutes at the reflux temperature, a shift of the absorption maximum to 286 nm occurs. The mixture is filtered on clay ("Clarcel"), and the filtrate is evaporated to dryness. The residue is chromatographed on a column filled with silica in an amount 35 times its weight, eluting with toluene. A fraction is recovered which gives 0.83 g of 6,17a,21-trimethylated product, which is purified by recrystallization from 95% ethanol. 3,20-dioxo-6,17a,21-trimethyl-19-nor-pregna-4,6-diene melts at 160°C.

IR spectrum: 1695 cm-<1> (CO in 20)

1680 cm"<1> (CO in 3)

1628, 1580 cm"<1> (delta-4.6)

UV spectrum: X max 288.5 nm 6 = 24280

Mass: m/e 340 (molar mass)

283 (M-57) loss of COCH2CH3

Elemental analysis: C23H32O2

NMR spectrum: (S,3H) at 0.71 ppm for CH3-18

(T,3H) at 1.05 ppm for CH3-22

(Dq) at 2.45 ppm for CH2-21

(S,3H) at 1.13 ppm for CH3-17a

(S,1H) at 5.95 ppm for H in C7

(S,1H) at 6.05 ppm for H in C5

Turnability: [a]D +18.90 (c = 0.53% dioxane

Example 3: 17a-ethyl-6-methyl-3,20-dioxo-19-nor-preqna-4,6-diene.

Step A: 3, 20-dioxo-17a-ethyl-19-nor-preqna-4-ene.

1 g of metallic calcium is dissolved in 40 ml of liquid ammonia at 60°C under an inert gas atmosphere. A solution of 1 g of 3-ethoxy-20-oxo-19-nor-pregna-3,5-diene in 18 ml of carefully dewatered tetrahydrofuran is then added in portions. The mixture is stirred for 1 hour, after which 9.8 ml of ethyl iodide is added. The reaction mixture is stirred for a further 1 hour, after which the ammonia is evaporated under reduced pressure in a hot water bath. A whitish paste is recovered, which is diluted in 100 ml of methanol, after which a 3N solution of hydrochloric acid is added until an acidic pH is reached, while cooling with a bath of acetone and ice.

After stirring for 60 minutes, the product is extracted with toluene. The toluene phases are separated and washed with water. The solvent is evaporated, whereby 0.81 g of the impure 17a-ethylated derivative is obtained, which by HPLC is shown to contain 41.6% pure 17a-ethyl derivative.

The compounds are purified by column chromatography on silica in an amount of 50 times the weight of the compound, using cyclohexane with 10% ether as solvent. The fraction corresponding to the 17a-ethylated derivative is evaporated to dryness. The dry residue is recrystallized from cyclohexane.

IR spectrum; 1705 cm-<1> (CO in 20)

1670 cm"<1> (CO in 3)

1620 cm'<1> (delta-4)

UV spectrum: X max 240 nm, 6 = 17520

NMR spectrum: (S,3H) at 0.70 ppm for CH3-18

(T,3H) at 0.75 ppm CH3 for ethyl 17a (S,3H) at 2.05 ppm for CH3-21

(S,1H) at 5.80 ppm for H in C4.

Step B: 3- ethoxy- 17a- ethyl- 20- oxo- 19- nor- preqna- 3, 5- diene.

The enol etherification is carried out according to the procedure described in step A in example 1, however starting with 9.6 g of the 17a-ethylated derivative from step A in example 3, which is previously dissolved in 29 ml of ethanol, and 9 is used, 6 ml of ethyl orthoformate and 0.048 g of p-toluenesulfonic acid and then 1 ml of triethylamine.

7.1 g of the enol ether are obtained, which corresponds to a yield of 68% of the pure compound.

IR spectrum: stretches at 1700 cm-<1> (carbonyl in 20)

at 1650 and 1620 (double bonds in 3 and 5) UV spectrum: X max 243 nm, 6 = 18520

NMR spectrum: (Q,2H) at 3.7 ppm (CH2 in ethoxy)

(S,3H) at 2.3 ppm (CH3 in 21)

(S,1H) at 5.2 ppm (H on C6)

(S,1H) at 5.8 ppm (H on C4)

Step C: 3- ethoxy- 6- formvl- 17a- ethyl- 20- oxo- 19- norpreqna- 3, 5-diene.

The formylation is carried out as described in step D in example 1. 0.5 ml POCl3 in 4.5 ml dimethylformamide is used as the formylation reagent. 2 g of potassium acetate in 40 ml of water are used as the hydrolysis solution. By starting with 1 g of 3-ethoxy-17a-ethyl-20-oxo-19-nor-pregna-3,5-diene, 1.18 g of impure 6-formylated derivative is obtained, as by chromatography on magnesium silicate and elution with dichloromethane gives 0.7 g of pure 3-ethoxy-6-formyl-17a-ethyl-20-oxo-19-nor-pregna-3,5-diene (yield = 65%).

X max: 323 nm and 220 nm.

Step D: 3. 2- dioxo- 6- methylene- 17a- ethyl- 19- nor- preqna- 4- en♦

The 6-methylene derivative is prepared from the 6-formyl derivative prepared in step C, following the same procedure as that described in example 1 (step E), starting with 0.5 g of 3-ethoxy-6-formyl-17a-ethyl-20- oxo-19-nor-pregna-3,5-diene in 65 ml of ethanol and 0.419 g of sodium borohydride, after which hydrolysis and dewatering are carried out using 8 ml of 2N sulfuric acid and 55 ml of water. 4.4 g of impure 6-methylene derivative is thereby isolated, corresponding to a yield of 76%. This compound appears to contain as an impurity small amounts of the 6-hydroxymethylated derivative, which is the intermediate product.

IR spectrum: 3400 cm-<1> (weak), corresponding to H-0

3080 cm"<1> (very weak), corresponding to H2O in methylene-6

1695 cm"<1> (CO in 20)

1660 cm-<1> (CO in 3)

UV spectrum: X max 258 nm

NMR spectrum: (S,3H) at 0.7 ppm (CH3-18)

(T,3H) at 0.75 ppm (CH3 in the ethyl group in 17a)

(S,3H) at 2.1 ppm (CH3-21)

occurrence of 3H (ethylenic) in

4.95 ppm

5.17 ppm

6.10 ppm

(Q) very weak at 3.74 ppm, corresponding to CH2 in the ethoxy group in the hydroxymethylated derivative, which shows that a certain amount of hydroxymethylated derivative is still present in the compound.

Step E: 3,20-dioxo-6-metvl-17a-etvl-19-nor-preqna-4,6-diene (compound of formula I).

A suspension of 5.5 g of palladium-on-carbon in 820 ml of ethanol is refluxed for 60 minutes. 4.1 g of 3,20-dioxo-6-methylene-17a-ethyl-19-nor-pregna-4-ene are then added to the suspension, and the course of the rearrangement reaction is followed by spectrophotometrically monitoring the isomerization. After heating for 8 minutes, the maximum absorption shifts to 288 nm. The reaction is then stopped, the suspension is filtered through clay ("Clarcel") and the filtrate is evaporated to dryness.

3.65 g of impure 6-methylated derivative are recovered. The compound is purified by column chromatography using silica in an amount 30 times the amount of the derivative, and the derivative recrystallized from a methanol solution thereof.

The pure compound melts at 162°C. Its rotatability [a]D is equal to zero (c = 1.26% dioxane).

IR spectrum: 1695 cm-<1> (CO in 20)

1660 cm"<1> (CO in 3)

1622, 1579 cm'<1> (delta-4.6)

UV spectrum: k max 288.5 e = 25880

Mass: m/e 340 340 molar mass

297 (M-43) loss of COMe

268 (M-72) loss of COMe and ethyl

Sm. p.: 162°C

Elemental Analysis: C23H3202

NMR spectrum: (S,3H) at 0.70 ppm (CH3-18)

(T,3H) at 0.75 ppm (CH3 in the ethyl group in 17a)

(dd,3H) at 1.83 ppm (CH3 in C6)

(S,3H) at 2.10 ppm (CH3-21)

(S,1H) at 5.95 ppm (H in C7)

(S,1H) at 6.05 ppm (H in C4).

Example 4 3,20-dioxo-6,21-dimethyl-17a-ethyl-19-norpreana-4,6-diene.

Step A: 3- methoxy- 17a- acetyl- 17B- acetoxy-estral, 3, 5(10)-triene.

1250 ml of a cation exchange resin of the polystyrenesulfone type is suspended in 4 1 of water. The resulting slurry is stirred for 12 hours, after which it is filtered and the resin is reslurried in 3.5 L of water. 50 g of mercuric acetate and 1 ml of acetic acid are then added, and the whole mixture is then stirred for 60 minutes. The resin is filtered off and washed thoroughly with water. 100 ml of the mercury resin is suspended in a solution of 100 g of megestrol = acetate, 50 ml of dioxane and 1500 ml of ethanol. After stirring for 20 minutes, 20 ml of water is added, and the entire mixture is refluxed for 15 hours. The reaction mixture is then filtered while hot and washed with ethanol. The filtrate is evaporated to dryness and washed with ethanol. The filtrate is evaporated again to dryness, and the residue is recrystallized from ethanol. 83 g of pure 3-methoxy-17a-acetyl-17p-acetoxy-estra-1,3,5(10)-triene are obtained, which corresponds to a yield of 79%.

IR spectrum: - Disappearance of stretches at 3265 cm"1 and 2100 cm"<1>

(C = C - H)

- Appearance of stretches at 1709 cm"<1>

(CO in 17a)

NMR spectrum: - Disappearance of (S,1H) at 2.65 ppm, corresponding to two H of C = C-H in 17a

- Appearance of (S,3H) at 2.05 ppm, corresponding to CH3 in C0CH3 in the 17a position

Step B: 3-Methox-17α-etvl-20-oxo-19-nor-preqnal-1,3,5(10)-triene.

A solution of 3.75 g of lithium in 800 ml of liquid ammonia is prepared under an argon atmosphere and at -60°C. A solution of 50 g of 3-methoxy-17a-acetyl-17p-acetoxy-estra-1,3,5(10)-triene in 750 ml of tetrahydrofuran is then added to the solution. After stirring for 3 hours, 270 ml of ethyl iodide are added over a period of 20 minutes, after which the mixture is stirred for a further 2 hours.

The ammonia is then evaporated under vacuum, using a hot water bath. The reaction mixture is then neutralized by the addition of dilute hydrochloric acid, and it is then extracted with methylene chloride. After separation and evaporation of the organic solution, 40 g of impure material are obtained (yield = 87% of the theoretical). This material is taken up in a mixture of 400 ml of methanol and 80 ml of methylene chloride.

After the mixture has been partially concentrated and evaporated, 34 g of pure 3-methoxy-17a-ethyl-20-oxo-19-nor-pregna-1,3,5(10)-triene are obtained, corresponding to a yield of 74%.

IR spectrum: - Disappearance of stretches

- at 1738 cm"<1>

- at 1268 cm"<1>

and at 1240 cm"<1> (acetoxy)

NMR spectrum: (S,3H) at 0.70 ppm (CH3-18)

(T,3H) at 0.80 ppm CH3 (17a-ethyl)

(S,3H) at 2.10 ppm (CH3-21)

(S,3H) at 3.70 ppm (CH3 in the methoxy group)

Step C: 3- methoxy- 17a- ethyl- 20- oxo- 21- methyl- 19- norpreqna-1. 3. 5( 10)- trien.

Under a nitrogen atmosphere and at 0°C, a solution of 1 ml of diisopropylamine and 6.5 ml of anhydrous tetrahydrofuran is prepared, to which 4 ml of a 5% methyllithium solution in ether is added dropwise. After stirring for 5 minutes, a solution of 1 g of 3-methoxy-17a-ethyl-20-oxo-19-nor-pregna-1,3,5(10)-triene in 22 ml of tetrahydrofuran is added dropwise. The temperature of the solution is allowed to return to room temperature and stirring is maintained for 80 minutes. The solution is cooled to 0°C, after which, with vigorous stirring, 2 ml of methyl iodide is added in one portion, and stirring is continued for 2 hours at room temperature. A precipitate of whitish mineral salts is visible, which is filtered off with suction.

The filtrate is evaporated to dryness and extracted with toluene. The toluene solution is washed with water and dried, and the toluene is distilled off. 1 g of impure 17a-ethyl,21-methyl derivative is obtained (yield 96%). The purification of this compound is carried out by crystallization from 20 ml of methanol. 0.8 g of the pure compound is thereby obtained, which is 17α-ethyl-20-oxo-21-methyl-19-nor-pregna-1,3,5(10)-triene.

Elemental analysis: C24<H>3402 = 354

NMR spectrum: (S,3H) at 0.65 ppm (CH3 in 17)

(T,3H) at 0.75 ppm (CH3 in the ethyl group in 17a)

(T,3H) at 1.10 ppm (CH3 in 22)

(Dq,2H) at 2.42 ppm (CH2 in 21)

(S,3H) at 3.78 ppm (CH3 in the methoxy group)

Step D: 3,20-dioxo-17α-ethyl-21-methyl-19-nor-preqna-4-ene.

At -50°C and under an argon atmosphere, a solution of 172 g of 3-methoxy-17a-ethyl-20-oxo-21-methyl-19-nor-pregna-1,3,5(10)-triene is added in 1750 ml of anhydrous tetrahydrofuran to 3000 ml of ammonia. Then, 90 ml of ethanol and 17.2 g of lithium are added three times, at 30 minute intervals. After stirring for 60 minutes, the ammonia is distilled off under vacuum,

using a bath of warm water.

The reaction mixture is stirred for a further 20 minutes, after which 400 ml of methanol and 4000 ml of water are added.

The steroid compound is extracted with methylene chloride and purified

• by column chromatography on silica. 3,20-dioxo-17a-ethyl-21-methyl-19-nor-pregna-4-ene is thereby recovered, corresponding to a yield of 54%. Crystallization from isopropyl ether gives the pure compound.

' IR spectrum: Stretches at 1705 cm-<1> (CO in 20)

1680 cm"<1> (CO in 3)

1620 cm"<1> (delta 4) Mass spectrum: m/e 343 molar mass

285 (loss of COC2H5)

> NMR spectrum: Disappearance of the peak (S,3H) at 3.7 ppm (CH3 in the methoxy group) and of the peaks at 7.2 ppm (aromatic ring).

Step E; 3- ethoxy- 17a- ethyl- 21- methyl- 20- oxo- 19- nor-preqna- 3, 5-> diene.

Enol etherification of 5 g of 3,21-dioxo-17a-ethyl-21-methyl-19-nor-pregna-4-ene is carried out in 10 ml of ethanol and 5 ml of ethyl orthoformate, after which extraction is carried out with benzene containing 1% triethylamine. By basic chromatography

< aluminum oxide with benzene as solvent, 4.8 g of enolet are obtained, which corresponds to a yield of 89%.

The analysis data is as follows:

IR spectrum: Disappearance of the stretch

» - at 1680 cm"<1> (CO in 3)

and appearance of the stretch

- at 1640 cm-<1> (divide by 5)

Mass spectrum: m/e 370 (molar mass)

342 (loss of C2H4)

< 285 (loss of C2H4 and COC2H5)

NMR spectrum: (T,3H) at 1.3 ppm (CH3 in the ethoxy group)

(block 2H) at 3.7 ppm (CH3 in the ethoxy group)

(S,1H) at 5.7 ppm (H on C6)

(S,1H) at 5.8 ppm (H on C4)

Step F: 3-ethoxy-6-formyl-17a-ethyl-21-methyl-20-oxo-19-nor-preqna-3,5-diene.

Formylation of 12.5 g of 3-ethoxy-17a-ethyl-21-methyl-20-oxo-pregna-3,5-diene in 87.5 ml of dimethylformamide is carried out using a formylation reagent consisting of 6.25 ml of POCl3 in 37 .5 ml of dimethylformamide.

The subsequent hydrolysis of the imonium salt is carried out by adding three successive portions of a solution of 37.5 g of potassium acetate in water. The yellow colored reaction product crystallizes out. It is filtered off and dried. 12.75 g of impure product is thereby obtained, corresponding to a yield of 95% of the theoretical.

IR spectrum: Stretches at 1699 cm'<1>

and at 1610 cm-<1> (conjugated C=C)

Mass spectrum: m/e 398

341 (loss of COC2H5)

NMR spectrum: (S,1H) at 6.20 ppm (ethylenic proton)

Appearance of (S,1H) at 10.25 ppm (CHO)

Step G: 3, 20- dioxo- 6- metvlen- 17a- etvl- 21- metvl- 19- nor- preqna- 4- en.

In an ice bath, 40 mg of sodium borohydride is added to a solution of 0.5 g of 3-ethoxy-6-formyl-17a-ethyl-20-oxo-21-methyl-19-nor-pregna-3,5-diene dissolved in 3, 8 ml of methanol and 2.2 ml of dimethylformamide. The mixture is then allowed to return to room temperature, and after 40 minutes of stirring, the UV spectrum shows that the maximum value has shifted to 250 nm.

A mixture of 1 ml of a 2 N sulfuric acid solution and 0.8 ml of dimethylformamide is added to the reaction mixture. After stirring for 30 minutes, the resulting mixture is neutralized by adding 2.5 ml of an aqueous sodium carbonate solution. The 6-methylene derivative crystallizes from the medium. It is filtered off and washed thoroughly with water. In the UV spectrum, the product shows an absorption maximum at 262 nm.

Step H: 3,20-dioxo-6,21-dimethyl-17α-ethyl-19-norpregna-4,6-diene (compound of formula I).

5 g of the impure 6-methylene derivative is subjected to isomerization in 245 ml of ethanol with 5 g of palladium-on-charcoal at the reflux temperature.

After stirring for 24 minutes, the UV spectrum shows the appearance of an absorption maximum at 288 nm. The mixture

is then filtered through clay ("Clarcel"), and the filtrate is evaporated to dryness. The dry residue is chromatographed on silica in an amount 60 times the weight of the residue, eluting with dichloromethane. The pure product is recrystallized from methanol, whereby 3,20-dioxo-6,21-dimethyl-17a-ethyl-19-nor-pregna-4,6-diene is obtained with the following analytical data:

Sm.p. = 180°C.

Drainability: [a]D = +4.4° (C = 1.26 dioxane) Elemental analysis: C24H3402 = 394

IR spectrum: 1700 cm'<1> (CO in 20)

1660 cm"<1> (CO in 3)

1630 and 1580 cm"<1> (double bonds in 4 and 6) NMR spectrum: (S,3H) at 0.70 ppm (CH3 in 18)

(T,3H) at 0.75 ppm (CH3 in 17a-ethyl)

(T,3H) at 1.05 ppm (CH3 in 21)

(Dd) at 2.40 ppm (CH2 in 21)

(dd,3H) at 1.85 ppm (CH3 on C6)

(S,1H) at 5.95 ppm (H on C7)

(S,1H) at 6.05 ppm (H on C4)

Pharmacological investigations of the new compounds Measurement of the relative affinity.

The applicant has carried out investigations to determine, for progesterone's target organ, the competitiveness of a number of steroid compounds in comparison with the reference compound (unlabelled progesterone). Progesterone labeled with <14>C is incubated with cytosols from the uterus, alone or in the presence of increasing concentrations of unlabeled steroid compounds (including unlabeled progesterone) distributed in a range R that extended from 1 to 1000 for both substances.

The following table shows the percentage amount of labeled progesterone that was still bound to the target organ, compared to the unlabeled competitor.

Compound D is 17α-acetoxy-6,21-dimethyl-3-oxo-19-nor-pregna-4,6-diene.

Compound A is 3,20-dioxo-6,17α-dimethyl-19-nor-pregna-4,6-diene.

Compound B is 3,20-dioxo-6-methyl-17α-ethyl-19-nor-pregna-4,6-diene.

Compound C is 3,20-dioxo-6,17a,20-trimethyl-19-nor-pregna-4,6-diene.

The data given in the table enable the calculation of the numerical values of the relative affinity.

The relative affinity (RA) is the ratio between the concentration at 50% inhibition (IC50) for a given steroid agent and for the specific unlabeled hormone used as a reference (here progesterone):

The relative affinity is thus expressed as a percentage value, based on the value RA for the reference hormone derivative or steroid derivative being 100%.

The IC50 represents an assessment of the IK (inhibition constant) of the tested steroids in relation to the binding of the reference steroid.

The measured values for RA thus give the following sequence: Compound B > nomegestrol acetate > compound A > progesterone > compound C > nomegestrol.

Discussion of the results

The six compounds tested belong to a series of derivatives closely related to nomegestrol acetate.

Two types of modification were relevant:

- introduction of a lower alkyl group in the 17a position

- extension of the acid chain in the 21 position with a methyl radical.

17α-methylation (compound A), 17α-ethylation (compound B) and 17α-acylation (17α-acetoxylation in the case of nomegestrol acetate) give rise to compounds whose affinity for the progestative target organ is at least equal to that of progesterone and corresponds to that of medroxyprogesterone -theron.

However, the disparities in affinity demonstrated at this stage of investigation indicate a hierarchy between these three compounds. In contrast, nomegestrol, which has the same side chain in the 17p position as the three other compounds tested (compound A, compound B and nomegestrol acetate), and which has a free hydroxyl group in the 17a position, exhibits a lower affinity, which is from 40 to 60 times weaker than for the three above-mentioned compounds.

If RA is set = 1 for nomegestrol acetate, as this is considered a reference compound, the following values can be derived from the following table, starting from nomegestrol acetate: compound B (0.17), compound A (0.81), compound C ( 0.45).

For one and the same substituent in the 17a position, lengthening the side chain in 21 results in a decrease in affinity for the progestative target organ.

However, it should be noted that a reduction of the affinity for the target organ "in vitro" does not necessarily entail any reduction of the biological activity "in vivo".

If the structural change causes a reduction in affinity, this can be followed by an improved bio-availability (more difficult breakdown, increased enterohepatic cycle, reduced complex formation for the plasma proteins). The resulting effect can thus be expressed through an increase in pseudogestagen activity.

Conclusions

Based on the fact that a weakened relative affinity in this series of new alkylated derivatives is of the order of 60% and that replacement of the hydroxy group in the 17a position with a lower alkyl group is possible, it has been established that mono- or dialkylation of 6- methyl-19-nor-pregna-dienes lead to highly active progestatives.

Claims (1)

Analogous process for the production of therapeutically active 6-methyl-19-nor-pregna-4,6-dienes which are 17a-alkylated and optionally 21-alkylated, and which have the formula I: where R' and R" are the same or different and are hydrogen or a straight-chain or branched alkyl group with 1-3 carbon atoms, and Rx is a straight-chain or branched lower alkyl group with 1-6 carbon atoms, characterized in that a 3-oxo-19- nor-pregna-4-ene derivative of formula IV: where R' and R" and Rx are as indicated above, subject to an enol etherification in acidic medium to form an enol ether of formula V: where R' and R" and Rx are as indicated above, and R2 is a lower alkyl radical, which compound is heated with a formylating agent of the Vilsmeier-Hack type to form a 6-formylated derivative of formula VI: where R' and R", Ri and R2 are as indicated above, this compound is reduced with a mixed alkali metal hydride to form a hydroxymethylated derivative of formula VII: where R', R", Rx and R2 are as indicated above, this compound is treated with a mineral or organic acid acid to form a 3-oxo-6-methylene derivative of formula VIII: where R', R" and Rx are as indicated above, and this compound is inverted with an isomerization catalyst to form the corresponding 6-methylated derivative of formula I .