FR2683527A1 - gem-Bisphosphonate (gem-Diphosphonate) prodrugs of steroids derived from cortisone - Google Patents

Abstract

The invention relates to the gem-bisphosphonate prodrugs of steroids derived from cortisone corresponding to the general formula (I) in which: - Y is either H or O or OH; - the 1-2 bond can be a double bond; - M<+> is a cation chosen from the group consisting of cations of alkali metals, the ammonium cation, the cyclohexylammonium cation, cations derived from nitrogenous bases and cations derived from amino acids; - X is or a -(CH2)n- alkylene group, n being equal to 1, 2, 3 or 4; and to the pharmaceutical compositions containing such prodrugs, intended for the treatment of bone diseases.

Description

Pro drug steroid gem-bisphosphonates derived from cortisone.

The present invention relates to the pharmaceutical field and more specifically to gem-bisphosphonate compounds constituting steroid prodrugs derived from cortisone.

The biological properties of gem-bisphosphonic acids are known which result from their structural analogy with inorganic pyrophosphoric acid and from their high biological stability. In particular, these gem-bisphosphonic acids have shown a great affinity for bone tissue which has led to their use in applications exploiting their action on bone metabolism and in particular in bone scintigraphy, in the treatment of PAGET disease. , rheumatoid arthritis and in the preventive treatment of osteoporosis.

Gem-bisphosphonic compounds have also been used to pharmacologically deliver an antineoplastic agent: methotrexate. This vectorization, described in French patent FR 2611 603, makes it possible to direct the antineoplastic agent towards the bone cells by taking advantage of the bone tropism of the gem-bisphosphonic compounds and makes it possible to administer methotrexate according to a favorable therapeutic activity / toxicity ratio.

Corticosteroids, for their part, have a well-known pharmacological interest. These biological compounds were isolated from the adrenal glands as early as 1935 and then chemically defined and pharmacomodulated in order to be able to be synthesized and used more easily as therapeutic agents.

The adrenal cortical glands secrete three series of steroid hormones: - glucocorticoids, including cortisone and hydrocortisone, which
have a very clear and well-known anti-inflammatory action,
at the origin of their wide therapeutic distribution,
- mineral corticosteroids such as aldosterone, the main hormone
controlling the renal elimination of sodium and potassium,
- adrenal androgens whose effects, outside their role
of prohormone, are unknown.

Thus, the anti-inflammatory properties of glutocorticoids have given rise to a great deal of pharmacomodulation research in order to reduce their side effects. In particular, this research led to the use of prednisolone or prednisone as substitute molecules for cortisol, the side effects of which such as water retention limited the use.

The main corticosteroids derived from cortisone are hydrocortisone or cortisol, prednisolone, prednisone, cortodoxone.

The objective of the present invention is to combine the high bone affinity of gem-bisphosphonic compounds with the therapeutic value of steroidal anti-inflammatory drugs derived from cortisone. More precisely, the aim of the invention is to produce prodrugs which can be conveyed to the bone cells constituting the target of the corticosteroid compounds and then be hydrolyzed at the level of these target cells and thus allow a specific action of the drug to this. level.

The aim of this vectorization is to improve the therapeutic index of corticosteroids, that is to say to reduce the quantity of active principle administered to the patient while obtaining an identical or improved therapeutic effect.

Another objective of the present invention is to provide an original route for the synthesis of these prodrugs from different building blocks.

According to the invention, the prodrugs gem diphosphonates of steroids derived from cortisone correspond to the general formula (I).

,n étant égal à 1, 2, 3 ou 4.in which - Y is either H or O or OH; - bond 1-2 maybe a double bond - M + is a cation chosen from the group consisting of metal cations
alkalis, the ammonium cation, the cyclohexylamonium cation, the cations derived from nitrogenous bases and the cations derived from amino acids; - X is an alkylene group

, n being equal to 1, 2, 3 or 4.

The general formula t1) relates to the proarogues according to the invention in their pharmaceutically acceptable galenic form, that is to say in the form of salts which make it possible to obtain an active principle whose pH is closest to the physiological pH (pH = 7 ).

dans laquelle - Y est soit H, soit O, soit OH; - la liaison 1-2 peut être une double liaison; - R est un radical alkyle inférieur en C1 à C6, linéaire ou ramifié - X' est un groupe -(CH2)- ou ou un groupe N-protégé

The invention also relates to such compounds in their gem-bisphosphonic acid form as immediate precursors to the gembisphosphonate compounds corresponding to general formula (I). These gembisphosphonic compounds correspond to the general formula (II)

in which - Y is either H, or O, or OH; - bond 1-2 can be a double bond; - R is a lower alkyl radical in C1 to C6, linear or branched - X 'is a group - (CH2) - or or an N-protected group

n being equal to 1, 2, 3 or 4 and R7 possibly being H, a lower alkyl radical
linear or branched C1 to C6 or an oxycarbonyl group.

dans laquelle R et X'ont la même signification que précédemment, puis à procéder aux étapes suivantes:
- silylation des esters gem-bisphosphonates obtenus;
- déprotection de la fonction amine, si une telle fonction est présente;
- méthanolyse des esters silylés et obtention de la forme hémisel de
la prodrogue.The invention also relates to a process for the synthesis of gem-bissphosphonate prodrugs of cortisone derivatives corresponding to the formula, consisting in esterifying the hydroxyterminal function of such derivatives by means of a gembisphosphonic synthon of general formula (III)

in which R and X 'have the same meaning as above, then proceed to the following steps:
- silylation of the gem-bisphosphonate esters obtained;
- deprotection of the amine function, if such a function is present;
- methanolysis of silyl esters and obtaining the hemisalt form of
the prodrug.

According to a preferred variant of implementation of this synthesis process, the step of silylation of the gem-bisphosphonate esters and the step of deprotection of the amine function are carried out simultaneously by the action of trimethylsilane bromide.

Advantageously, said gem-bisphosphonic synthon of general formula (III) is chosen from the group consisting of:
- the N-protected forms of the acids 2 - amino -4,4- bis (dialkylphos
phono) butanoic;
- 3,3 - bis (dialkylphosphono) propanoic acids;
- 4,4 - bis (dialkylphosphono) butanoic acids.

Preferably, said gem-bisphosphonic synthon of general formula (III) is chosen from the group consisting of 2 - N - (tert - butyloxycarbonyl) amino - 4,4 - bis (diethylphosphono) butanoic acid.

- 3,3-bis (diethylphosphono) propanoic acid;
- 4,4 - bis (diethylphosphono) butanoic acid.

With a particularly interesting dewlap, the N-protected forms of gem-bisphosphonic building blocks corresponding to formula (III) are obtained: - by the action of ditertiobutyl dicarbonate in chloroform, by
absence of base, on the unprotected form of the gem-bisphospho compound
corresponding nate; - by saponification of the intermediate compound gem-bisphosphonate N
protected obtained.

The invention also relates to a building block consisting of a 4,4 bis (dialkylphosphono) butanoic acid as well as an original process for obtaining such a building block.

According to the invention, this process consists of:
- forming an alkyl 2-carboxyalkyl-4'4-bis (dialkylphosphono) butanoate by condensation of a dialkyl malonate with a tetraalkyl vinylidene gem-bisphosphonate;
- saponifying the alkyl 2-caiboxyalkyl-4,4-bis (dialkylphosphono) butanoate obtained to form an alkyl 2-carboxy-4,4-bis (diphosphono) butanoate diacid;
- Heat this diacid to obtain a 4,4-bis (dialkylphosphono) buta osque acid.

Finally, the invention relates to a pharmaceutical composition for the preventive or curative treatment of bone diseases comprising an active principle or a mixture of active principles in the form of at least one gembisphosphonate prodrug corresponding to general formula (I).

The invention will be more easily understood by virtue of the non-limiting exemplary embodiments which will follow illustrating the synthesis of various steroid gembisphosphonate prodrugs derived from cortisone.

Example 1
a) Preparation of 2-N- (ten-butyloxycarbonyl) amino -4-4- bis (diethylphosphono) butanoic acid 13
This synthon is obtained from ethyl 2-amino-4,4 bis (diethylphosphono butyrate) 22, itself obtained according to a known method by condensation of ethyl glycinate with vinylidene gem-tetraethyl bisphosphonate.

Ethyl 2-amino-4,4-bis (diethylphosphono) butanoate 22 (8.05 g. 20 mmol) is dissolved in chloroform (30 ml). The ditertiobutyl dicarbonate 59 (4.36 g, 20 mmol) in solution in chloroform (15 ml) is added rapidly. The lively and exothermic reaction is maintained by reflux for 1 hour 15 minutes. After evaporation of the solvent under reduced pressure, the protected amino ester 60 is isolated in a quantitative yield (10 g) and in a sufficient purity to be used as it is. for subsequent saponification.

To this end, the latter compound is diluted in methanol (20 ml) and potassium hydroxide (1.12 g, 20 mmol) dissolved in water (10 ml) is added at room temperature. Saponification is immediate; the methanol is evaporated
on a rotary evaporator and the residue taken up in water (20 ml) is extracted with ether (2
X 15 ml). The aqueous phase is then acidified (pH 1) with a solution of KHSO4
1M and extracted with chloroform (5 X 20 ml). Acid 13 is isolated as a
white solid after drying (MgSO4), then evaporation of the solvent. This compound can
be crystallized from hexane or petroleum ether.

b) Estérification
Le prednisolone 3 (2.16 g, 6 mmol) et l'acide 2-N-(tert-butyloxycarbonyl) amino -4,4- bis (diéthylphosphono) butancffque 13 (2.85 g, 6 mmol) sont mis en solution dans le chlorure de méthylène (150 ml). Le dicyclohexylcarbodiimide DCC (1.24 g, 6 mmol) est additionné, ainsi que le 4-N,N-diméthylaminopyridine DMAP (0.07 g, 0.6 mmol) et l'agitation est poursuivie 48 h.

The reactive scheme can be translated as follows:

b) Esterification
Prednisolone 3 (2.16 g, 6 mmol) and 2-N- (tert-butyloxycarbonyl) amino -4,4- bis (diethylphosphono) butancffque 13 (2.85 g, 6 mmol) acid are dissolved in chloride. methylene (150 mL). Dicyclohexylcarbodiimide DCC (1.24 g, 6 mmol) is added, as well as 4-N, N-dimethylaminopyridine DMAP (0.07 g, 0.6 mmol) and stirring is continued for 48 h.

The reaction mixture is concentrated before being filtered to remove the dicyclohexylurea formed. After complete evaporation of the solvent under reduced pressure, 5.7 g of a white powdery solid are obtained, corresponding to the gem-bisphosphonate ester prodrug.

This powder is dissolved in a minimum of methylene chloride, before being chromatographed on a silica gel column with an eluent of ethyl acetate, then ethyl acetate / ethanol 1: 1; the ester prodrug is thus isolated. The overall yield obtained is 80%.

c) Silylation of gem-bisphosphonate esters and release of the amine function of the prodrug
To the prodrug (3.9 g, 4.8 mmol) dissolved in methylene chloride (20 ml) is added bromotrimethylsilane (5.1 ml, 38.4 mmol). The mixture is left under stirring for 48 h, before the solvent is evaporated off under reduced pressure.

The residue is taken up in methanol (25 ml), stirred for 1/2 h at room temperature, then evaporated to produce the prodrug in its tetrakisphosphonic acid and free amine form.

d) Switching to gem-bisphosphonic hemisels
A solution of sodium methoxide (0.486 g, 9 mmol) in methanol (10 ml) is added to the preceding tetrakisphosphonic prodrug (4.5 mmol) in solution in methanol (5 ml) and stirring continued for a few minutes.

The insoluble 10Ac hemisalin thus formed is filtered, before being dried in an oven under vacuum over P205 (50 ° C.). Yield: 2.5 g (92%).

Example 2
a) Preparation of 3.3-bis (diethylphosphono) propanoic acid 15
This compound was obtained by condensing ethyl bromoacetate on the sodium carbanion of tetraethyl methylene diphosphonate in THF. The procedure was as follows.

The sodium hydride (0.24 g, 10 mmol) is covered with 111F (20 ml) under a nitrogen atmosphere. Tetraethyl methylene diphosphonate (2.88 g, 10 mmol) is added at a temperature close to 10 ° C. and stirring continued until the evolution of hydrogen gas has ceased. Ethyl bromoacetate 61 (1.67 g, 10 mmol) is added and stirring continued for 1 hour 30 minutes. After addition of a saturated aqueous solution of ammonium chloride (10 ml) and evaporation of the THF, the residue is extracted. with chloroform (3 X 15 ml). The organic phase is dried (MgSO4) and evaporated under reduced pressure (intermediate yield: 86 t;).

The ester 62 is taken up in methanol (10 ml) and the potassium hydroxide (0.5 g, 9 mmol) in solution in water (5 ml) is added at a temperature between 15 and 20 "C. Stirring is carried out. continued for 15 h, the methanol is evaporated off and the basic residue extracted with ether (5 ml). After acidification to pH = 1 with a saturated aqueous solution of KHSO4, the aqueous phase is extracted with ethyl acetate ( 3 X 15 ml). This last dried organic phase (MgSO4) leads to the desired acid 15 by evaporation under reduced pressure. The preparation of compound 15 can be represented by the following reaction:

b) Esterification
The esterification step is carried out identically to that described in Example 1 by replacing prednisolone with cortodoxone 5 and using 3,3-bis (diethylphosphonopropanoic acid) as a building block.

This step makes it possible to obtain the prodrug in ester form with a yield of 94%.

c) Silvlation of ester functions
The silylation step is carried out in the same manner as that described in Example 1. Since the starting gem-bisphosphonic synthon 15 does not carry any amine function, silylation is limited to deprotecting the acid functions.

d) Switching to bisphosphonic hemisels
The step of obtaining the pharmaceutically acceptable hemisalt galenic form is carried out in the same way as in Example 1 and makes it possible to obtain the prodrug 12Bc

Example 3
a) Preparation of 4.4-bis (diethylphosphono) butanoic acid 14
Firstly, ethyl 2-carboxyethyl-4,4-bis (diethylphosphono) butanoate 24 is prepared by adding ethyl malonate (3.2 g; 20 mmol) to vinylidene gem-bisphosphonate at room temperature. tetraethyl (6g; 20 mmol) in a sodium ethoxide medium (0.14 g; 2 mmol) in ethanol The reaction mixture is then neutralized by adding a saturated aqueous solution of ammonium chloride (10 mml) and the diester is isolated after extraction in ethyl acetate.

This compound 24 (9.25 g, 20 mmol) in solution in '111F (20 ml) is saponified by adding potassium hydroxide (2.24 g, 40 mmol) in solution in water (5 ml) at a temperature of the same range. 15 ° C. The mixture is left under stirring for 15 h at room temperature and the liii ™ is evaporated off under reduced pressure. An aqueous solution of KHSO4 (1M) (about 20 ml) is added, until neutralization, to the residue. evaporation obtained, then the mixture is extracted with ethyl acetate (2 × 10 ml). The aqueous phase is then acidified to pH = 1 by adding a saturated aqueous solution of KHISO4 and again extracted with ethyl acetate (3X15 ml). This last organic phase is dried (MgSO4) and the solvent is evaporated to give the diacid 2-carboxy-4,4-bisphosphobutanoate of ethyl, which undergoes decarboxylation by heating at 1300C for 3 h, leading directly to the expected acid 14

b! Esterification
The esterification step is carried out in the same way as that described in Example 1. The cortisone derivative used is hydrocortisone 4. The synthon used is 4,4 bis (diethylphosphono) butanoic acid 14.

This step makes it possible to obtain the prodrug in ester form with a yield of 92%.

c) Sylilafion of ester functions
The silylation step is carried out in the same way as that described in Example 1.

d) Switching to bisphosphonic hemisels
The step of obtaining the galinic form is carried out in the same way as in Example 1 and makes it possible to obtain the prodrug 11Cc.

The anti-inflammatory potency of the steroid gem-bisphosphonate prodrugs derived from cortisone 1ici, 12Bc was verified in animals by administering these prodrugs to rats with a model of arthritis induced by Freund's adjuvant. rate of daily intake of 5 mm / kg for 21 days.

Examples 1 to 3 do not restrict the invention to only the gem-bisphosphonic prodrugs obtained. In particular, all the steroids derived from cortisone can be esterified by the building blocks described and in particular the building blocks 13, 14, 15.

Claims (10)

1. Pro drugs gem-bisphosphonates of steroids derived from cortisone characterized in that they correspond to the general formula (I)

in which - Y is either H or O or OH; - the 1-2 bond may be a double bond; - M + is a cation selected from the group consisting of metal cations alkalis, the ammonium cation, the cyclohexylamonium cation, the cations derived from nitrogenous bases and cations derived from amino acids - X is an alkylene group - (CH2) n- or

n being equal to 1, 2, 3 or 4. 2.Gem bisphosphomic steroid drugs derived from cortisone characterized in that they correspond to the general formula (II)

- Y is either H, or O, or OH; - bond 1-2 can be a double bond; - R is a lower alkyl radical in C1 to C6, linear or branched - X 'is a group - (CH2) - or or an N-protected group

n being equal to 1, 2, 3 or 4 and R ′ possibly being H, a linear or branched C1 to C6 lower alkyl radical or an oxycarbonyl group. R1 possibly being H, a lower alkyl radical C1 to C6 linear or branched or an oxycarbonyl group. 3. Process for the synthesis of prodrugs according to claim 1, characterized in that it consists in esterifying the hydroxyterminal function of a steroid compound derived from cortisone using a gem-bisphosphonic synthon of general formula

wherein R and X 'have the same meaning as in claim 2, then proceeding to the following steps: - silylation of the gem-bisphosphonate esters obtained; - deprotection of the amine function, if such a function is present; - methanolysis of the silyl esters and obtaining the hemi-salt form of the prodrug. 4. Method according to claim 3 characterized in that said step of silylation of gem-bisphosphonate esters and said step of deprotection of the amine function are carried out simultaneously by the action of trimethylsilane bromide. 5. Method according to one of claims 3 or 4 characterized in that said gem-bisphosphonic synthon of general formula III is chosen from the group consisting of: - the N protected forms of the acids 2 - amino - 4,4 - bis (dialkylphos phono) butanoic; - 3,3 - bis (dialkylphosphono) propanoic acids; - 4,4 - bis (dialkylphosphono) butanol acids. 6. Method according to claim 5 characterized in that said gembisphosphonic synthon of general formula (III) is 2 - N - (tert - butyloxycarbonyl) amino - 4,4 - bis (diethylphosphono) butanoic acid 13. - 4,4 - bis (diethylphosphono) butanolic acid 14. - 3,3 - bis (diethylphosphono) propanoic acid 15; 7. Method according to one of claims 3 to 6 characterized in that the N-protected forms of gem-bisphosphonic synthons corresponding to formula (III) are obtained: - by the action of ditertiobutyl dicarbonate in chloroform, in absence of base, on the unprotected form of the gem-bisphospho compound corresponding nate; - by saponification of the intermediate compound gem-bisphosphonate N protected obtained. 8. Synthon for carrying out the process according to claim 6, characterized in that it consists of a 4,4-bis (dialkylphosphono) butanoic acid. 9. Process for preparing a building block according to claim 8, characterized in that it comprises the steps of: - forming an alkyl 2-carboxyalkyl-4,4-bis (diallylphosphono) butanoate by condensation of a dialkyl malonate on a tetraalkyl vinylidene gem-bisphosphonate - saponifying the alkyl 2-carboxyalky1-4,4-bis (dialkylphosphono) butanoate obtained to form an alkyl 2-carboxy-4,4-bis (diphosphono) butanoate diacid; - heating this diacid to obtain a 4,4-bis (dialkylphosphono) butanic acid. 10. Pharmaceutical composition for the preventive or curative treatment of bone diseases comprising an active principle or a mixture of active principles in the form of at least one prodrug gem-bisphosphonate of a cortisone derivative according to claim 1.