WO1997049711A1

WO1997049711A1 - Derivatives of carboxy gem-bisphosphonates with antitumor activity, a process for preparing them and pharmaceutical compositions containing them

Info

Publication number: WO1997049711A1
Application number: PCT/EP1997/003190
Authority: WO
Inventors: Valeria Livi; Simonetta D'alo'; Silvano Spinelli; Marco Conti
Original assignee: Boehringer Mannheim Italia S.P.A.
Priority date: 1996-06-26
Filing date: 1997-06-12
Publication date: 1997-12-31
Also published as: ITMI961290A1; ITMI961290A0; IT1284070B1; AU3260897A

Abstract

The present invention relates to conjugates of carboxy gem-bisphosphonic acids with alkylating agents. Such derivatives are endowed with remarkable antitumor activity and with specific activity on bone resorption. The present invention also relates to a process for preparing them and to pharmaceutical compositions containing them.

Description

DERIVATIVES OF CARBOXY GEM-BISPHOSPHONATES WTTH ANTI-TUMOR ACTIVITY. A PROCESS FOR PREPARING THEM AND PHARMACEUTICAL COMPOSITIONS CONTAINING THEM

The skeletal system is the third more common site of metastases and more than 80% of all dead cancer patients show bone tumors at autopsy. Bone metastases account for a significant proportion of cancer-related morbidity, causing derangement in calcium metabolism and bone marrow involvement and are responsible for the sevre consequences in patients with cancer, such as pain, pathological fractures, compression of the spinal cord and hypercalcemia (Drew et al. , Osseous complication of malignancy, Lokich, J.J. ed. Clinical cancer medicine: treatment tactics Boston: G.K. Hall Medical Publisher, 1980, 97-112). The bone lesions are one of the most important features associated with bone tumors. Most of the local lesions caused by bone metastases are known to be a direct effect on the mineralized matrix or an indirect effect of tumor-stimulated bone resorption. The process of bone resorption is mediated predominantly by multmucleated osteoclasts and involves the release of bone mineral and the degradation of bone matrix The osteoclasts resorb the bone across a specialized area of the cell membrane known as "ruffled border". The resorption of bone is associated with the release of lysosomal enzymes and collagenaseε by the osteoclasts, as well as with the local production of acid which is responsible for causing release of mineral from the bone

(Mundy, G.R., Bone resorption and turnover in health and disease, Bone, 1987, 8, S9-S16).

Therefore it appears that the discovery of a drug able to inhibit both tumor growth and bone destruction is a primary target in antitumor research.

Gem-diphosphonic acids and salts thereof are known and employed in the therapy of osteoporosis and in the treatment of bone resorption (see EP 96.931, EP 252.504, BE 896.453, BE 903.519, DE 3.016.289, DE 3.540.150, DE 2.534.391, DE 3.512.536). However, for none of the above compounds antitumor activity is described.

DE 3.425.812 (Blum et al. ) describes derivatives of 1,1-diphosphonic acids, characterized by a bis[(halo- genoalkyl)amino]phenyl residue, as agents useful in the treatment of bone tumors. The bone tropism typical of the diphosphonic acids is in fact coupled with the cytotoxic activity typical of molecules carrying dialkylating functionality. No activity on bone resorption is however described.

Furthermore, in WO 88/06158 diphosphonic analogues of metotrexate are described as agents useful in the treatment of bone tumors.

Therefore it appears that none of the above mentioned compounds has shown efficacy in acting contemporaneously both as antitumor agent and as inhibitor of bone resorption. Particularly, the compounds disclosed in DE 3.425.812, even if they are conjugates between a diphoshonate, active on bone resorption, and an alkylating, antitumor agent, have maintained only the latter activity. This demonstrates that the activity of the final compound is not automatically foreseeable simply adding the corresponding activities of the two starting intermediates. WO 92/18512 claims however conjugates between bis- phosphonic acids and alkylating agents characterized in having the two molecules linked by means of amino acid moieties. The amide bond, which can probably be metabolically hydrolyzed, is said to be responsible for the activity of these compounds, which maintain the efficacy both as antitumor agents and as inhibitors of bone resorption. However said molecules are not able to completely inhibit the bone resorption, especially after long times from treatment (see Table I). We have now found that the compounds of the general formula (I ) :

v ^V

wherein: R and R^ represent halo-ethyl (2-chloroethyl, 2- bromoethyl, 2-iodoethyl) or, taken together with the nitrogen atom to which they are linked, are a 1- aziridinyl residue of formula

,N A-

(A) is linear or branched ( C, -Cc )alkylene , phenylene or an aralkyl chain of formula

wherein m is an integer between 1 and 5; n is an integer between 1 and 6; B.2 i^s hydrogen or a hydroxy group; R₃ hydrogen or (C^-^ )alkyl;

R₄ represents hydrogen or (C^-C^)alkyl, are endowed with a remarkable antitumor activity and contemporaneously are able to totally inhibit the bone resorption even after long time from treatment. The diastereoisomers, the racemates and the pure enantiomers of the compounds of formula (I) are encompassed in the scope of the present invention.

In the scope of the present invention are furthermore encompassed the pharmaceutically acceptable salts of the compounds of formula (I), such as those with inorganic bases such as salts with alkali (for example sodium or potassium) or alkaline-earth metal ions (for example calcium or magnesium) or ammonium salts; the salts with organic bases such as methylamine, ethylamine, propylamine, isopropylamine, butylamine, tert-butylamine , dimethylamine , diethylamine , dietha- nolamine, trimethylamine , triethylamine, piperidine, pyridine, picoline, dicyclohexylamine; the salts with inorganic or organic acids such as hydrochloric, hydrobromic, sulfuric, phosphoric, nitric, formic, acetic, trifluoroacetic, maleic, fumaric, tartaπc, methanesulphonic or paratoluenesulphonic acid; the salts with amino acids such as aspartates, glutamates or salts with lyεine or arginine.

R and R^ are preferably a 2-haloethyl group; (A) is preferably a group of formula

n is preferably the integer 2 or 3;

R2 is preferably a hydroxy group;

R₃ and R₄ are preferably hydrogen.

Particularly preferred compounds are those in which

R and R^ are a haloethyl group, (A) is a group of formula

n is the integer 2 or 3 and R₃ and R^ are hydrogen.

Most preferred compounds are those in which R and R-, are a 2-chloroethyl group, (A) is a group of formula

n is the integer 2 or 3, R2 is a hydroxy group and R3 and R4 are hydrogen.

The compounds of the general formula (I) can be prepared following a process which comprises the condensation reaction of a compound of formula (II):

^<

wherein R, R^, (A) and R₄ have the above meanings, with a bis-phosphonate of formula (III):

wherein n has the above meaning, R2' has the above meanings or is a O-G group, in which G is a suitable protecting group for a tertiary alcohol; R₃' has the above meanings except hydrogen; T is a hydroxy or a carboxy-activating group, to give compounds of formula

(

which can be converted into the compounds of formula ( I ) by removal of the protecting groups optionally present and/or by optional hydrolysis of the phosphomc esters to give the corresponding phosphomc acids and optional salification of the obtained compounds with pharmaceutically acceptable acids or bases.

Diastereoisomers of the compounds of formula ( I ) optionally present may be separated by selective crystallization or by purification via liquid chromatography.

Enantiomers of the compounds of formula (I) optionally present may be separated from the racemic mixtures following methods of optical resolution known to those skilled in the art, while not obtained directly m the synthesis starting from optically active reagents

The protecting groups to which reference is made in the present invention are all protecting groups for an alcoholic or carboxylic oxygen atom, such as ethers, esters and silyl derivatives.

Preferred examples of G protecting groups are silyl ethers and particularly tertbutyl dimethyl silyl ether.

Such protecting groups can be removed by means of reaction well known to the skilled artisan, such as removal in basic conditions in the case of esters and removal in acidic conditions in the case of ethers and silyl derivatives. The phosphomc esters can be hydrolyzed with particular selective agents, such as trimethylsilyl iodide. When in the reaction of compounds of formula (II) with compounds of formula (III) these latter are used as free carboxylic acids (T = OH), the reaction is generally conducted in the presence of a condensing agent such as N,N' -dicyclohexyl carbodnmide , N-cyclo- hexyl-N' -morpholmoethyl carbodnmide , N-ethyl-N' -( 3- dimethylammo)propyl carbodnmide, N,N' -carbonyl bis- (lmidazole), phosphorus oxychloride, phosphorus trichlo¬ ride, thionyl chloride, oxalyl chloride, ethyl- chloroformate, isobutylchloroformate, morpholi- noethylisomtπle or similar reagents. When T is a carboxy-activatmg group , examples of -C(=0)T groups are acyl halides, symmetrical or mixed anhydrides (for example with methanesulfomc , acetic, isobutyric, pivalic, trifluoroacetic acids); activated amides (for example with lmidazole , 1 ,2, 4-tπazole ) ; azide; activated esters (for example paramtrophenyl ester, methoxymethyl ester, 2 ,4-dmιtrophenyl ester, pentachlorophenyl ester, hydroxysuccmimido ester, 1- hydroxy-2-( lH)-pyrιdone ester, 1-hydroxybenzotrιazole ester) and similar groups. A particularly preferred activating T group is the hydroxysuccmimidyl group of formula

The condensation reaction of the compounds of formula (II) with the compounds of formula (III) can be performed in the presence of an inorganic base such as an alkali carbonate or bicarbonate, an alkali or alkaline-earth hydroxide or of an organic base such as triethyl amine, tributyl amine, pyridme, 4- dimethylammo pyridme, N-alkylmorpholine, N,N- dialkylaniline or similar bases. The pH is preferably maintained not above pH = 9. The reaction temperature can range from -40"C to the boiling temperature of the solvent, according to the chosen activating group, preferably between -10^*C and

50^βC.

The preferred solvents are inert organic solvents, such as pyπdine, N,N-dιmethyl formamide or aceto- nitrile, or mixtures thereof with water in various proportions .

The reaction times are variable with the activating group and the substrate which are chosen and can be comprised between 30 minutes and 48 hours.

Particularly preferred reaction conditions are those which provide for the use of triethyl amine, in molar excess on the reagents, in a 1:10 water/acetonitrile mixture and at a temperature comprised between 0°C and room temperature.

The compounds of formula (II) are known compounds, commercially available and/or preparable with methods known to those skilled in the art, such as those described in : J. Med . Chem. , 24, 1304 (1981); CA 51: 3066d (1957); BE 905.971; CA 104: 141897 (1986); J. Med. Chem. , 7, 468 (1964); J. Med. Chem., 6, 85 (1963); Cancer Chem. Rep. , 50, 685 (1966); J. Med. Chem. , 21, 16 (1977); J. Org. Chem. , 26, 1554 (1961); J. Org. Chem. , 26, 1674 (1961); CA 64: 10267g (1966); J. Chem. Soc , 2994 (1960); Biochem. Pharmacol. , 11, 847 (1962); Biochem. Pharmacol. , 12, 833 (1963); CA 73: 131293c (1970); Biochem. Pharmacol. , 5, 192 (1960), Int J.

Pept. Protein Res. , 36, 308 (1990).

The compounds of formula (III) in which R₂ ' is hydrogen and T is a OH group are known compounds or can be prepared according to experimental methods known to those skilled in the art [Synthesis, 661 (1991);

Phosphorus, sulfur, Silicon Relat. Elem. , 88(1-4), 1-13

(1994); FR 2683527; Zh. Obshch. Khim., 61(12), 2698

(1991); Bioorg. Khim. , 12(9), 1282 (1986); J Organometal. Chem., 13(1), 199 (1968)].

The compounds of formula (III) in which R₂' is O-G

(wherein G is hydrogen or a suitable protecting group) and T is a OH group can be synthesized according to the following process comprising the steps of: (a) reacting equimolar amounts of a cyclic anhydride of a suitable dicarboxylic acid and of an alcohol of formula R^-OH, wherein R^ is an alkyl group of 1 to

4 carbon atoms or is a benzyl group, optionally substituted, or allyl group, obtaining the intermediate of formula (IV):

^< H

The reaction is performed in an inert solvent, preferably dimethyl formamide, in the presence of a base, preferably pyridme, and at a temperature ranging from room temperature to the boiling point of the reaction mixture; (b) suitably activating the non-esterified carboxylic group present in intermediate (IV), transforming it for example into an acyl halide, an anhydride or an activated ester such as hydroxyεuccmimido ester A preferred example of the activation of the carboxylic group in intermediate (IV) is its transformation into acyl chloride by means of thionyl chloride;

(c) reacting the intermediate obtained in step (b) with a trialkyl phosphite P(OR₃' )o (preferably tπmethyl phosphite) m an inert solvent such as chloroform and at a temperature ranging from -10°C to room temperature, obtaining the intermediate of formula

(V)-

(d) reacting the intermediate of formula (V) with a dialkyl phosphite HP(0)(OR₃' )2 (preferably dimethyl phosphite) in the presence of a base, preferably an organic base such as dialkyl or trialkyl amines , obtaining the intermediate of formula (VI):

(e) optionally protecting the OH group with a suitable protecting group selected from those suitable for a tertiary alcohol;

(f) deprotectmg the -COOR₅ ester group by means of hydrolysis reaction in basic or acid medium and m conditions in which the other R₃ ' protecting groups and the group optionally present on the alcoholic functionality are not affected or, in the case Re is a benzyl or allyl group, by catalytic hydrogenation or in the presence of hydrogen donors such as ammonium formate or sodium hypophosphite. A particularly advantageous alternative process for obtaining the intermediates of formula (III) wherein R₂ ' is a -O-silyl group is that which replaces in step (d) the dialkyl phosphite with a dialkyl silyl phosphite of formula (VII):

obtaining directly the intermediate of formula (III¹):

wherein the R_β groups can be the same or different. A particularly preferred silyl group is the tertbutyl dimethyl silyl group. Such a process allows to obtain in one step the intermediate already protected at the alcoholic oxygen, thus avoiding the step (e) of oxygen protection

The intermediates of formula (III) in which both T and R₂ ' are OH groups are known (DE 2117880, NL

6610762) The intermediates of formula (III) m which T is a

OH group and R₂ ' is a -0-Sι(Rg)₃ group are new

A further object of the present invention are therefore the intermediates of formula (III) with T = OH and R₂ ' = -0-Sι(Rg)₃, that is the intermediates of formula (VIII)-

wherein n and R₃' have the above meanings and the Rg groups, which can be the same or different, are selected from the group comprising linear or branched (C^- C₄)alkyl or phenyl .

A particularly preferred meaning of Sι(R_g)₃ group is tertbutyl dimethyl silyl group.

The derivatives of formula (III) in which T is a suitable activating group are obtained from the derivatives with T = OH by means of reactions well known to those skilled in the art

The compounds of the invention have been tested "m vivo" against Walker 256/B mammary carcinoma in the rat mtratibially implanted. Once inoculated in the cavity of the tibia's bone marrow, said tumor grows inside the bone causing osteolytic lesions, paraneoplastic hypercalcemia and it invades the surrounding tissues producing a measurable tumor mass. It is thus possible to measure both the antitumor activity against the extraosseous tumor and the antiosteolytic effect

(Cancer, 72(1), 91 (1993)).

The tumor Walker 256/B has been obtained by NCI

Frederick Cancer Facility and maintained m male rats

CD1 by means of subcutaneous transplant of tumor fragments of about 1 cm diameter every 10 days.

To perform the experiment the rats are injected with 2.5xl0⁶ tumor cells; the animals are anaesthesized with a mixture of 10 mg/kg of Ketalar (Park-Davis) and 5 mg/kg of Rompun (Bayer). Once transplanted inside the tibia, the tumorε growε causing osteolytic lesions associated with an increased activity of the osteoclasts. To obtain an mjectable cell suspension, the tumor fragments are desegregated by means of enzymatic digestion using collagenase type IV (Sigma) at a concentration of 400 U/ml for 20 minutes at 37°C

The compounds of the invention have been administered i.v. in the days 1, 4 and 7 after the tumor transplant The extraosseous tumor mass has been measured at day 14 after the tumor transplant. The antitumor activity has been determined as TWI% (tumor weight inhibition %) calculated accordmg to the following formula- TWI% = (100 - TW mean _{treated anιrn} /TW mean_controls) x 100 wherein the TW for each animal is given by the formula.

TW = i (ab)² wherein a and b are respectively the maximum and minimum diameter of the tumor mass in millimeters

The osteolytic lesions have been radiologically evaluated at days 8 and 16 following the tumor transplant. The animals have been anaesthesized, placed in prone position on a Rx-film (X-OMAT MA, S.p.A. ). The bone lesion degree has been determined accordmg to the following scores: absence of lesions +/- low dihomogeneity + high dihomogeneity ++ isolated lesions +++ wide lesions

On the base of such scores the Destruction Index (Dl) has been calculated:

Dl = no. of lesions x degree of lesion/total no. of animals .

Dl values lower or equal to 1 mean a good bone protection. A value of Dl = 0 means a complete absence of lesions and thus a total protection or repair.

The compounds of the invention have been tested on this experimental model with respect to the prior art compounds and have shown an higher activity not only as far as the antitumor activity against the extraosseous tumor is concerned, but also as antiosteolytic agents. Table I shows the comparison data for a molecule representative of the compounds of formula (I) Table i Antitumor activity of 4-[bis(2-chloroethyl)amino]-N- ( 5, 5-diphospho-5-hydroxy-l-pentanoyl)-(L)-phenylalanine trisodium salt (example 1), 4-[4-(bis(2-chloroethyl)- amino)phenyl]-l-hydroxybutane-l ,1-diphosphonic acid trisodium salt (compound A, Blum et al.), N-[[4-bis(2- chloroethylamino) )-(L )-ρhenylalanyl]-(L)-alanyl]-4-ami- no-l-hydroxybutane-1 ,1-diphoεphonic acid trisodium salt (compound B, WO 92/18512) against the Walker 256/B mammary carcinoma in the rat (it/iv; days 1,4,7).

Compound dose(mg/kg) TWI% Dl day 8 day 16

Example 20 83 0 . 75 0 . 25 30 84 0 . 0 0 . 0

A 55 67 2 . 2 B 20 80 0 . 6 0 . 7

Yet a dose of 20 mg/kg, the compound of the invention shows a continuous tendency to a bone lesions repair, with Dl values which pass from 0.75 after 8 days to 0.25 after 16 days. At the same dosage, compound B shows on the contrary the opposite tendency, being detected an increase of the destruction index at day 16. This demonstrates that compound B is not able of causing a true long lasting bone tissue repair.

Furthermore, the compounds of the invention resulted active in an experimental model of human multiple myeloma on the laboratory animal. The human multiple myeloma is a tumor which has as a target the plasma cells and it is sensitive to alkylating agents such as melphalan Bone damages are often associated to the tumor, causing pain and fractures It appears therefore that a drug able to carry the alkylating agent to the bone and on the other hand to preserve or repair the bone from the damages caused by the tumor it is an extremely interesting target

The test is performed by inoculating intravenously

(i.v. ) the human multiple myeloma HS-Sultan cells in SCID ( immunodeflcient ) mice at day 0, followed by the i.v. treatment with a compound of the invention at days

15, 18 and 21.

The activity of the compounds of the invention has been evaluated with respect to the following parameters: - Mean Survival Time (MST) in comparison with not treated mice (which have a MST of 30 days after the tumor inoculation); evaluation of the histologic parameters (bone marrow invasion and entity of the osteolytic lesions) according to the methods previously described.

The compounds of the invention are endowed with a low acute toxicity and are well tolerated m the animals . The high water solubility of the compounds of the invention allows to prepare parenteral and oral pharmaceutical compositions.

The compounds of formula ( I ) , when administered to men and animals carrying tumors susceptible of alkylating agent therapy, in variable dosages from 1 mg to 1200 mg per square meter of body surface, are able to cause the regression of said tumors and to allow the bone tissue repair, avoiding m this way the pathological manifestations associated with the bone lesions The effective dosage of the compounds of the invention can be determined by an expert clinician accordmg to known conventional methodε

The correlation between dosages used in the animals of various species and in the man (given m mg/m² of body surface) is described in Freiπch, E.J et al ,

Cancer Chemother. Rep. , 50, n.4, 219-244, May 1966

The tumors susceptible of therapy with the compounds of the present invention are those susceptible of therapy with alkylating agents In particular, can be advantageously treated multiple myeloma, osteosarcoma, bone metastasis, breast, ovary and testiε carcinomas

The pharmaceutical compositions containing the compounds of formula (I) are comprised in the scope of the invention.

Such pharmaceutical compositions may contain any amount of the compounds of formula (I) having antitumor activity in the mammals against tumors susceptible of alkylating agent therapy. The pharmaceutical compositions may contain, in addition to at least one compound of formula (I), pharmaceutically compatible excipients, in order to allow the administration by any route, such as oral, parenteral, intravenous, mtradermal, subcutaneous or topic routes, in liquid or solid form.

An administration route of the compounds of formula (I) is the oral route. Oral compositions will generally include an inert diluent or an edible carrier. They may be included in gel capsules or compressed into tablets.

Other formε suitable for the oral administration are capsules, pills, elixirs, suspensions or syrups.

The tablets, pills, capsules and similar compositions may contain the following ingredients (in addition to the active substance): a binder such as a microcrystalline cellulose, gum tragacanth or gelatin; an excipient such as starch or lactose; a disintegrating agent such as alginic acid, primogel, corn starch and the like; a lubricant such as magnesium stearate; a glidant such as colloidal silicon dioxide; a sweetening agent such as sucrose or saccharine or a flavoring agent such as peppermint, methyl salicylate or orange flavor. When the chosen composition is in form of capsules, it may contain in addition a liquid carrier such as a fatty oil. Other compositions may contain other various materials which modify the physical form, such as coating agents (for tablets and pills) such as sugar or shellac. The materials used in the preparation of the compositions should be pharmaceutically pure and not toxic at the employed dosages.

For the preparation of pharmaceutical compositions by parenteral administration route, the active ingredient may be incorporated into solutions or suspensions, which may include in addition the following components: a sterile diluent such as water for injection, saline solution, oils, polyethylene glycols, glycerin, propylene glycol or other synthetic solvents; antibacterial agents such as benzyl alcohol; antioxidants such as ascorbic acid or sodium bisulphite, chelating agents such as ethylenediammotetraacetic acid, buffers such as acetates, citrates or phosphates and agents for adjusting the solution tomcity such as sodium chloride or dextrose The parenteral preparation may be included m ampoules, disposable syringes or glass or plastic vials

The invention is further described by the following examples and preparationε . PREPARATION 1 - mono benzyl glutaric acid

A εolution of glutaric anhydride (22.8 g) in benzyl alcohol (20.7 ml), anhydrous pyridme (250 ml) and dimethylformamide (25 ml) is refluxed for about 4 hours 30 minutes, then the solvent is evaporated off under reduced pressure and the residue is redissolved in 500 ml of ethyl acetate. The organic phase is then washed with 1 N hydrochloric acid (2x100 ml) and with water (3x100 ml), then it is basified with 200 ml of 1 N sodium hydroxide and with 200 ml of saturated solution of sodium hydrogen carbonate The organic phase is separated, while the aqueous phase is neutralized by addition of 37% hydrochloric acid and extracted with methylene chloride (400 ml) The organic extracts are dried over sodium sulfate and the solvent is evaporated under reduced pressure, obtaining 32.8 g of product PREPARATION 2 - mono benzyl glutaroyl chloride

A solution of mono benzyl glutaric acid (32.8 g) m 250 ml of anhydrous toluene is added with 21.5 ml of thionyl chloride, then it is heated at 65°C for 1 hour. The solvent is evaporated off under reduced pressure and the residue is dissolved in toluene and evaporated, repeating this step twice. 35 g of product as pale pink oil are obtained.

PREPARATION 3 - 5-(dimethoxyphosphmoyl)-5-ketopentanoιc acid, benzyl ester 35 g of mono benzyl glutaroyl chloride are dissolved m 150 ml of anhydrous chloroform and the solution is cooled to 0°C. 18 ml of trimethyl phosphite are slowly dropped (during 1 hour 20 minutes), then the temperature is raised to room temperature After an additional hour the solvent is evaporated off under reduced pressure obtaining 45 g of product as an oil PREPARATION 4 - (tertbutyldimethylsilyl)-dιmethyl phosphite

To a suspension of 6.4 g of sodium hydride (60% in oil) in 255 ml of anhydrous tetrahydrofuran, cooled at 0°C, are added dropwise 13 4 ml of dimethyl phosphite, then the reaction mixture lε refluxed for 2 hours 30 minutes. Afterwards, the temperature is raised to room temperature and 20 g of tert-butyldimethylsilyl chloride are added The reaction mixture is again refluxed for a total of 16 hourε, then the sodium chloride which separates is filtered off and the solvent is evaporated under reduced pressure.

23.62 g of product are obtained. PREPARATION 5 - 5,5-(bis-dimethoxyphosphmoyl )-5-(tert- butyldιmethylsilyloxy)pentanoic acid, benzyl ester

12 8 g of (tertbutyldιmethylsιlyl)-dιmethyl phosphite are dropped into 18 g of 5- (dimethoxyphosphmoyl )-5-ketopentanoιc acid, benzyl ester, cooled at 10^*C. At the end of the addition, the temperature is raised to room temperature. After 4 hours the reaction mixture is dissolved m 500 ml of ethyl acetate and the organic phase obtained is washed with 5° sodium hydrogen carbonate (3x70 ml), then with water

(3x70 ml), then with 5% potassium carbonate (3x70 ml) and finally with a saturated solution of sodium chloride

(70 ml). The organic phase is dried over sodium sulfate and the solvent is evaporated under reduced pressure, obtaining 25.9 g of residue which is purified by silica gel chromatography (eluent AcOEt - AcOEt/acetone 1:1) to give 17 g of the pure product as an oil.

PREPARATION 6

According to the methods described in preparations

1-5, starting from the suitable reagents and using the suitable trialkyl silyl halides, the following esters are prepared:

5 , 5-(bιs-dιmethoxyphoεphmoyl )-5-(tertbutyldimethylsi- lyloxy)pentanoιc acid, allyl ester;

4,4-(bιε-dιmethoxyphoεphmoyl )-4-( tertbutyldimethylsi- lyloxy)butanoιc acid, benzyl ester; 5 , 5-(bis-diethoxyphosphmoyl )-5-( tertbutyldimethylsi- lyloxy)pentanoιc acid, benzyl ester;

5 , 5- ( bιs-dιmethoxyphosphmoγl ) - 5- ( tπmethylεilyloxy ) - pentanoic acid, benzyl ester;

3 , 3- (bis-dimethoxyphosphmoyl )-3-( tertbutyldimethyl- silyloxy)propanoιc acid, allyl ester;

8 ,8-(bis-dimethoxyphosphinoyl )-8-( tertbutyldimethylsi- lyloxy)octanoιc acid, benzyl ester;

⁷ , 7-( bis-dimethoxyphosphmoyl )-7-

( trimethylsilyloxy)heptanoιc acid, benzyl ester; 5 , 5-(bis-diethoxyphoεphmoyl )-5-(phenyldimethylsilyl- oxy)pentanoιc acid, benzyl ester; 6,6- (bis-dimethoxyphosphinoyl )-6-(phenyldimethylεilyl- oxy)hexanoιc acid, benzyl ester.

PREPARATION 7 - 4,4-bis(diethoxyphosphinoyl )butanoic acid, N-hydroxysuccinimido ester To a solution of 4 , 4-bιs(diethoxyphosphinoyl )- butanoic acid (1.28 g; prepared as described in

Synthesis, 661-2 (1991)) and of N-hydroxy succinimide

(0.613 g) in 35 ml of tetrahydrofuran are added dropwise

0.636 ml of morpholinoethyl isomtrile, while maintaining the temperature at about 0°C. The temperature is thus raised to room temperature and the reaction mixture is kept under stirring for 20 hours. After this time, the εolvent is evaporated off under reduced pressure and the residue is redissolved in 70 ml ethyl acetate and washed first with water (40 ml), then v/ith 1 N hydrochloric acid (40 ml) and with a saturated solution of sodium chloride (2x40 ml). The organic phase is dried over sodium sulfate and the solvent is evaporated off under reduced pressure to give 1.3 g of product.

EXAMPLE 1 - 5,5-bis(dimethoxyphosphinoγl)-5-(terbutyldi- methylsilyloxy)pentanoic acid

To a solution of 5 , 5-(bis-dimethoxyphosphinoyi )-5- ( tertbutyldimethylεilyloxy)pentanoic acid, benzyl eεter (4.5 g; preparation 5) in 110 ml of dimethylformamide are added portionwise 0.9 g of 10% palladium on carbon. The reaction mixture is hydrogenated under atmospheric pressure and at room temperature for 2 hours 45 minutes (consuming 0.372 ml of hydrogen). The catalyst is then eliminated by filtration through a celite plug and the solvent is evaporated off under reduced pressure. 4 g of the product as a colorless oil are obtained

N.M R (200 MHz) in CDC1₃ 3 85 ppm (m, 6H); 1 85-2.4 ppm (m, 6H); 0.9 ppm (s, 9H) ; 0.2 ppm (s, 6H).

EXAMPLE 2 According to the method described in example 1, starting from the ester of preparation 6, the following acids are obtained:

4 ,4-(bis-dimethoxyphosphmoyl )-4- ( tertbutyldimethylsi- lyloxy)butanoιc acid, benzyl ester, 5 , 5-(bis-diethoxyphosphinoyl )-5-(tertbutyldimethylεi- lyloxy)pentanoιc acid, benzy] ester;

5, 5-(bis-dimethoxyphosphmoyl )-5-( tπmethylsilyloxy )- pentanoic acid, benzyl ester;

3, 3-(bis-dimethoxyphosphmoyl )-3-(tertbutyldimethylsi- lyloxy)propanoιc acid, allyl ester;

8 ,8-(bis-dimethoxyphosphmoyl)-8-( tertbutyldimethylsi- lyloxy)octanoιc acid, benzyl eεter;

7,7-(bιs-dιmethoxyphosphmoyl )-7-(tπmethylsιlyl- oxy)heptanoιc acid, benzyl ester, 5 , 5-(bis-diethoxyphosphinoyl )-5-(phenyldimethyIsllyl¬ oxy)pentanoιc acid, benzyl ester;

6 ,6-(bιs-dιmethoxyphosphιnoyl )-6-(phenyldimethylsilyl¬ oxy)hexanoιc acid, benzyl ester.

EXAMPLE 3 - 4-[bis{2-chloroethyl )amino]-N-[4 ' ,4 ' -bis- (diethoxyphosphinoyl )-l ' -butanoyl]-(L)-phenylalanme

To a suspension of 4-[bιs( 2-chloroethyl )ammo]- (L)- phenylalanine (melphalan; 0.78 g) in 50 ml of dimethoxyethane and 0.575 ml of triethylamine is added dropwise a solution of 4 , 4-bιs(diethoxyphosphinoyl )- butanoic acid, N-hydroxysuccmimido ester (1.3 g, preparation 7) in 10 ml of dimethoxyethane After 24 hours under stirring at room temperature the solid completely dissolves. The solvent is then evaporated off under reduced pressure and the residue is redissolved in ethyl acetate (100 ml) and washed with 0.5 N (2x60 ml) and with a saturated sodium chloride solution (2x60 ml).

The organic phase is dried over sodium sulfate and the solvent is evaporated off under reduced pressure, obtaining 1 6 g of residue which is purified by silica gel chromatography (eluents methylene chlo- ride/methanol/acetic acid 95:5:1, then methylene chloπde/methanol/acetic acid 90:10:1). 1.25 g of product are obtained.

N.M.R. (200 MHz) in CDC1₃: 7.12 ppm (d, 1H) ; 7 ppm (d, 2H); 6.55 ppm (d, 2H) ; 4.72 ppm (dd, 1H); 4.2 ppm (m, 8H); 3.6 ppm (m, 8H); 3 ppm (dd, 1H); 2.8 ppm (dd, 1H); 2.1-2.7 ppm (m, 4H ) ; 1.35 ppm (m, 12H).

EXAMPLE 4 - 4-[bis(2-chloroethyl)amino]-N-[4' ,4' - diphospho-1 ' -butanoyl]-(L)-phenylalanine disodium salt

To a solution of the product of example 3 (1.1 g) in 35 ml of chloroform are added dropwise 2.24 g of tπmethylsilyl iodide, maintaining the temperature at about 0°C. After 2 hours at 0°C and 1 hour at room temperature, the solvent is evaporated off under reduced pressure and the residue is redissolved in water (80 ml) The pH of the solution is adjusted to pH = 5 by addition of 1 N sodium hydroxide, then by addition of ethanol an oil separates which is removed by decantation The oil obtained is crystallized from methanol, obtaining 0.9 g of product. [α]_D = -2.6° (c = 1.05% in HC1 1 N)

N.M.R. (200 MHz) in D₂0- 7.2 ppm (d, 2H); 6.85 ppm [ z , 2H); 4.37 ppm (dd, IH); 3.75 ppm (ε, 8H); 3.07 ppm (dd ,

IH); 2.85 ppm (dd, IH); 2.45-2.6 ppm (m, 2H ) ; 1.75-2.25 ppm (m, 2H) .

EXAMPLE 5 Following the methodε described m preparation 7 and in examples 3-4, starting from the suitable reagents, the following gem-diphoεphonic acids are obtained:

4-[bιs( 2-chloroethyl )ammo]-N-[ 5 ' , 5 ' -dιphospho-1 ' -penta- noyl] ( L )-phenylalanme disodium salt;

4-[bιs(2-chloroethyl )ammo]-N-[8 ' ,8' -dιphospho-1 ' -octa- noyl]-(L )-phenylalanme disodium salt;

4-[bis ( 2-bromoethyl )amino]-N-[4 ' , 4 ' -dιphospho-1 ' -buta- noyl] ( L )-phenylalanιne disodium salt; 4-[bιε( 2-chloroethγl )ammo]-N-[3 ' , 3 ' -dιphospho-1 ' -propa- noyl]-(L )-phenylalanιne disodium salt;

4-[N'-azιridιnyl]-N-[4 ' , 4 ' -dιphospho-1 ' -butanoyl]-(L )- phenylalanme disodium salt.

EXAMPLE 6 - 5,5-bis(dimethoxyphosphinoyl)-5-(tertbutyl- dimethylsilyloxy)pentanoιc acid, N-hydroxysuccinimido ester

To a solution of 5 , 5-bιs(dimethoxyphosphmoyl )-5-

( tertbutyldimethylsilyloxy)pentanoιc acid (3.7 g; example 1) m 82 ml of anhydrous tetrahydrofuran are added, under nitrogen atmosphere and at 0°C, 1.42 g of

N-hγdro.^vysuccιnιmιde . A solution of morpholmoethyl isonitrile (1.73 g) in 1 ml of tetrahydrofuran is added dropwise, then the temperature is raised to room temperature and the reaction mixture is kept 20 hours under stirring. The solvent is then evaporated off under reduced pressure and the residue is redissolved m ethyl acetate (100 ml), then the organic phase is washed with

1 N hydrochloric acid (50 ml), after that with a sodium hydrogen carbonate saturated solution (50 ml), finally with a saturated solution of sodium chloride (50 ml). The organic phase is dried over sodium sulfate and the solvent is evaporated off under reduced pressure, obtaining 4 g of product.

EXAMPLE 7 - 4-[bis( 2-chloroethyl )amino]-N-[5 ' , 5 '-bis(di¬ methoxyphosphmoyl)-5 ' -(tertbutyldimethylsilyloxy)-l ' - pentanoyl]-(L)-phenylalanine

To a suspension of 4-[bis( 2-chloroethyl )amino]-( L)- phenylalanine (melphalan; 1.85 g) in 5.6 ml of water, 28 ml of acetonitrile and 1.24 g of triethylamine is slowly added dropwise (during about 1 hour) a solution of the product of example 6 (3 g) in 28 ml of acetonitrile. At the end of the dropping, the reaction mixture is kept under stirring at room temperature for 40 minutes, then the solvent is evaporated off under reduced pressure and the residue is redissolved in 100 ml of ethyl acetate. The organic phase is washed with 1 N hydrochloric acid (2x40 ml) and with water (2x40 ml), then it is dried over sodium sulfate and the solvent is evaporated off under reduced pressure. 3.7 g of product are obtained. N.M.R. (200 MHz) in dg-DMSO: 12 ppm (b, IH); 8.1 ppm (d, IH); 7.05 ppm (d, 2H); 6.65 ppm (d, 2H); 4.32 ppm (m, IH); 3.6-3.85 ppm (m, 20H); 2.65-3 ppm (m, 2H); 1.6- 2.2 ppm (m, 6H); 0.85 ppm (s, 9H ) ; 0.15 ppm (s, 6H ) . EXAMPLE 8 - 4-[bis(2-chloroethyl )amino]-N-[5' , 5'-di- phospho-5 '-(tertbutyldimethylsilyloxy)-l '-pentanoyl]- (L)phenylalanine

To a solution of the product of example 7 (2.7 g) m 20 ml of anhydrous acetonitrile, kept under stirring and under nitrogen atmosphere at 0°C, 5 g of trimethylsilyl bromide are added. The temperature is then raised to room temperature and the stirring is kept for a total of 4 hours 30 minutes. The solvent is evaporated off under reduced pressure and the residue is partitioned between water (100 ml) and ethyl acetate

(100 ml). The organic phase is separated and dried over sodium sulfate, then the solvent is evaporated off under reduced pressure, obtaining 1.88 g of the product.

N.M.R. (200 MHz) m dg-DMSO: 8.06 ppm (d, IH); 7.05 ppm (d, 2H); 6.65 ppm (d, 2H); 4.3 ppm (m, IH); 3.7 ppm (ε, 8H); 2.65-3 ppm (m, 2H) ; 1.6-2.2 ppm (m, 6H) ; 0.85 ppm (s, 9H); 0.15 ppm (s, 6H) . EXAMPLE 9 - 4-[bis(2-chloroethyl)ammo]-N-[5 ' ,5'- diphospho-5'-hydroxy-1 '-pentanoyl]-(L)-phenylalanine trisodium salt

To a solution of 2.7 g of the product of example 8 in 105 ml of acetonitrile are added 1.65 ml of 37% hydrochloric acid and the reaction mixture is kept under stirring at room temperature for 28 hours. The reaction mixture is evaporated and the residue is partitioned between 90 ml of water and 100 ml of ethyl acetate. The aqueous phase is separated and treated with a 20% sodium hydroxide solution until pH = 4.8, then the opalescent solution is cooled to 0°C and added with 250 ml of ethanol. A white solid separates which is kept at 0"C under stirring for about 50 minutes. After filtration and drying under vacuum at 50°C, 1.55 g of the product are obtained.

N.M.R. (200 MHz) in D₂0 + DC1 (pH = 1): 7.55 ppm (s, 4H), 4 67 ppm (dd, IH); 4.1 ppm (t, 4H); 3.65 ppm (t,

4H); 3.35 ppm (dd, IH ) ; 3.05 ppm (dd, IH); 1.7-2.35 ppm

(m, 6H)

EXAMPLE 10 Accordmg to the methodε deεcribed m examples 6-9, starting from the intermediates of example 2 and from the suitable substituted ammoacids, the following gem- diphoεphonic acids are prepared-

4-[bιε(2-chloroethyl)amιno]-N-[4' ,4' -dιphospho-4 ' -hydro- xy-1 ' -butanoyl]-(L)-phenylalamne trisodium salt;

4-[bιs( 2-chloroethγl )amιno]-N-[3 ' , 3 ' -dιphospho-3 '-hydro- xy-1 ' -propanoyl]-(L )-phenylalanine trisodium salt;

4-[bιs( 2-chloroethyl )ammo]-N-[8 ' ,8 ' -dιphospho-8 ' -hydro- xy-1 ' -octanoyl]-(L )-phenylalamne trisodium salt; 4-[bιs(2-chloroethγl)ammo]-N-[7 ' , 7 ' -dιphoεpho-7 ' -hydro- xy-1 ' -heptanoyl]-(L )-phenylalamne trisodium salt;

4-[bιε( 2-chloroethyl )ammo]-N-[6 ' , 6 ' -dιphospho-6 ' -hydro- xy-1 ' -hexanoyl]-(L)-phenylalanme trisodium salt;

4- [N' -azιπdmyl]-N-[5 ' , 5 ' -dιphospho-5 ' -hydroxy- 1 ' -pen- tanoyl]-( L ) -phenylalanine trisodium salt,

4-[bιs(2-chloroethyl )ammo]-N-[4 ' , 4 '-dιphoεpho-4 ' -hydro- xy-1 ' -butanoyl]-(L)-phenylalanine , methyl ester disodium salt;

4-[bιε(2-chloroethyl)ammo]-N-[3' ,3' -dιphospho-3 ' -hydro- "y-1 ' -propanoyl]-(L)-phenylalanme , ethyl ester disodium salt.

EXAMPLE 11

According tc the methods described m examples 6, 7 and 9, starting from the intermediates of example 2 and from the suitable substituted ammoacids, the following esters of bis-phosphomc acids are prepared: 4-[bis( 2-chloroethyl )ammo]-N-[3 ' , 3 ' -(bis-dimethoxy- phoεphinoyl )3 ' -hydroxy-1 ' -propanoyl ]- ( L )-phenylalanme;

4-[bιε( 2-chloroethyl )ammo]-N-[8 ' ,8 ' -(bis-dimethoxy- phoεphinoyl )-8 '-hydroxy-1 ' -octanoyl]- ( L )-phenylalanine; 4-[bιs(2-chloroethyl)ammo]-N-[7' ,7 ' -(bis-dimethoxy- phosphinoyl )-7 ' -hydroxy-1 ' -heptanoyl]-(L )-phenylalanine;

4-[bis( 2-chloroethyl )amιno]-N-[6 ' , 6 ' -(biε-dimethoxy- phoεphmoyl )-6 ' -hydroxy-1 ' -hexanoyl]-(L )-phenylalanme;

4-[N'-aziridmyl]-N-[5' ,5' -(biε-dimethoxyphosphmoyl )- 5 ' -hydroxy-1 ' -pentanoyl]-(L )-phenylalanine,^•

4-[bis( 2-chloroethyl )amino]-N-[4 ' , 4 ' -( biε-dimethoxy- phoεphinoyl )-4 ' -hydroxy-1 ' -butanoyl]-(L )-phenylalanine , methyl ester;

4-[bιs( 2-chloroethyl )amιno]-N-[3 ' , 3 ' -(bis-dimethoxy- phosphinoyl )-3 ' -hydroxy-1 ' -propanoyl]-(L)-phenylalanme, ethyl ester;

4-[bis(2-chloroethyl )ammo]-N-[5 ' , 5 ' -(bis-diethoxy- phosphinoyl )-5 ' -hydroxy-1 ' -pentanoyl]-( L)-phenylalanme .

Claims

Compounds of general formula (I)

wherein:

R, R^ halo-ethyl ( 2-chloroethyl, 2-bromoethyl , 2- iodoethyl) or, taken together with the nitrogen atom to which they are linked, are a 1-aziridinyl residue;

(A) is linear or branched (C^-C^ )alkylene , phenylene or an aralkyl group of formula

wherein m is an integer from 1 to 5; n is an integer from 1 to 6;

R₂ is hydrogen or a hydroxy group;

R₃ is hydrogen or (C^-C₄ )alkyl;

R₄ is hydrogen or (C2~C₄ )alkyl , their diastereoisomers , racemic mixtures and pure enantiomers and salts thereof with pharmaceutically acceptable acids or bases.

2. Compounds according to claim 1, wherein (A) is a group of formula

3. Compounds according to claim 2, wherein R₃ and R₄ are hydrogen

4 Compounds according to claim 3, wherein n is the integer 2 or 3 and P and R^ are a 2-chloroethyl group

5 Compounds according to claims 1-4, wherein R₂ is a hydroxy group.

6. Compound according to claim 1, selected in the group comprising-

4-[bιs(2-chloroethyl )ammo]-N-[4 ' ,4'-dιphospho-1 '-buta¬ noyl] (L)phenylalamne disodium salt; 4-[bιs(2-chloroethyl)ammo]-N-[5' ,5 '-dιphospho-1 '-penta¬ noyl]-(L)-phenylalanme disodium salt;

4-[bιs(2-chloroethyl )amιno]-N-[8' ,8'-dιphospho-1 '-octa- noyl]-(L)-phenylalanme disodium salt; 4-[bιε( 2-bromoethyl )ammo]-N-[4 ' ,4 '-dιphospho-1 '-buta- noy. ]-(L)-phenylalanine disodium salt;

4-[bιs(2-chloroethyl )ammo]-N-[3 ' ,3 '-dιphospho-1 '-propa- noyl]-(L)-phenylalanιne disodium salt;

4-[N'-azιrιdιnyl]-N-[4' ,4'-dιphospho-1' -butanoyl]-(L)- phenylalanme disodium salt; 4-[bιs(2-chloroethyl)ammo]-N-[5' ,5' -dιphospho-5'-hydro- xy-1 '-pentanoyl]-(L)-phenylalanine trisodium salt, 4-[bis(2-chloroethyl)amino]-N-[4'_/4'-dιphospho-4'-hydro- xy-l '-butanoyl]-(L)-phenylalanme trisodium salt; 4-[bιs(2-chloroethyl)ammo]-N-[3 ' ,3 '-dιphoεpho-3'-hydro- xyl '-propanoyl]-(L)-phenylalanιne trisodium salt;

4-[bιs(2-chloroethyl )ammo]-N-[8' ,8'-dιphospho-8' -hydro- xy-1 ' -octanoyl]-(L )-phenylalanme trisodium salt;

4-[bιs(2-chloroethyl )ammo]-N-[7 ' , 7 '-dιphospho-7 ' -hydro- xy-1 ' -heptanoyl]-(L )-phenylalanme trisodium salt, 4-[bιs(2-chloroethyl)ammo]-N-[6' ,6' -dιphospho-6 ' -hydro- xy-1 ' -hexanoyl]-(L )-phenylalanine trisodium salt;

4-[N'-azιrιdιnyl]-N-[5' ,5' -dιphospho-5 ' -hydroxy-1 ' -pen¬ tanoyl]-( L )-phenylalanme trisodium salt; 4-[bιs( 2-chloroethyl )ammo]-N-[4 ' ,4 ' -dιphospho-4 ' -hydro- xy-1 ' -butanoyl]-(L)-phenylalanme, methyl ester disodium salt;

4 - [ bιε ( 2 -chloroethyl ) ammo ] -N- [ 3 ' , 3 ' -dιphoεpho- 3 ' -hydro- xy-1 ' -propanoyl ] - ( L ) -phenylalamne , ethyl ester disodium salt ;

4-[bιs( 2-chloroethyl )ammo]-N-[3 ' , 3 ' -(bis-dimethoxy- phosphinoyl )-3 ' -hydroxy-1 ' -propanoyl]-( L )-phenylalanme; 4-[bιs( 2-chloroethyl )ammo]-N-[8 ' ,8 '-(bis-dimethoxy- phosphmoyl )-8 ' -hydroxy-1 ' -octanoyl]- (L)-phenylalanine; 4-[bιs( 2-chloroethyl )ammo]-N-[7 ' ,7 ' -(bis-dimethoxy¬ phosphmoyl )-7 '-hydroxy-1 '-heptanoyl]-(L )-phenylalanme; 4-[bιs( 2-chloroethyl )ammo]-N-[6 ' ,6 ' -(bis-dimethoxy- phoεphmoyl )-6 ' -hydroxy-1 ' -hexanoyl]-( L )-phenylalanme; 4-[N'-azιrιdιnyl]-N-[5' ,5' -(bis-dimethoxyphosphmoyl )- 5 ' -hydroxy-1 ' -pentanoyl]-(L)-phenylalanme; 4-[bιε(2-chloroethyl )ammo]-N-[4 ' , 4 ' -(bis-dimethoxy- phosphinoyl )-4'-hydroxy-l' -butanoyl]-( L )-phenylalanine , methyl ester;

4-[bιs(2-chloroethyl)amιno]-N-[3' ,3' -(bis-dimethoxy- phosphmoyl )-3 ' -hydroxy-1 ' -propanoyl]-(L)-phenylalanme , ethyl ester; 4-[bιs(2-chloroethyl )ammo]-N-[5 ' , 5 ' -(bis-diethoxy- phoεphmoyi )-5 ' -hydroxy-1 ' -pentanoyl ]- ( L)-phenylalanme

7. Compound according to claim 6, wherein such compound is:

4-[bis(2-chloroethyl)amino]-N-[5' ,5' -diphospho-5 ' -hydro- xy-1 ' -pentanoyl]-(L)-phenylalanine trisodium salt.

8. A process for the preparation of the compounds of formula ( I ) :

wherein:

R, R₁ halo-ethyl ( 2-chloroethyl , 2-bromoethyl, 2- iodoethyl) or, taken together with the nitrogen atom to which they are linked, are a 1-aziridinyl residue;

(A) is linear or branched (C^-C^ )alkylene, phenylene or an aralkyl group of formula

wherein m is an integer from 1 to 5; n is an integer from 1 to 6;

R₂ is hydrogen or a hydroxy group;

R₃ is hydrogen or (C-, -C₄ )alkyl;

R₄ is hydrogen or (C^-C₄ )alkyl , their diastereoisomers , racemic mixtures and pure enantiomers and salts thereof with pharmaceutically acceptable acids or bases, comprising the following steps :

(a) condensation reaction of the compounds of formula

(II):

wherein n has the above meaning, R2 ' has the above meanings or is a group 0-G, in which G is a suitable protecting group for a tertiary alcohol, R₃' has the above meanings except hydrogen, T iε a hydroxy group or a group which activateε the carboxylic functionality.

(b) selective removal of the protecting groups optionally present and/or optional hydrolysis of the phosphonic esters to give the corresponding acids;

(c) optional salification with pharmaceutically acceptable acids or bases;

(d) optional separation of diastereoisomers or enantiomers.

9. Compounds of formula (VIII):

wherein n is an integer from 1 to 6, R-, ' is linear or branched (C₁-C₄)alkyl and the Rg groups, which can be the same or different, are selected from the group comprising linear or branched (C -C₄)alkyl and phenyl group, as intermediates.

10. Compound accordmg to claim 9, wherein said compound is:

5 , 5-bιs(dimethoxyphosphmoyl)-5-(tertbutyldimethylsilyl- oxy)pentanoιc acid.

11. A process for the preparation of the compounds of formula (VIII):

wherein n is an integer from 1 to 6, F₃' is linear or branched (C^-C₄ )alkyl and the Rg groups, which can be the same or different, are selected in the group comprising linear or branched (C₁-C₄)alkyl and phenyl group, comprising the following steps: (a) reaction of a cyclic anhydride of a suitable dicarboxylic acid with an alcohol of formula Rr-OH, wherein R₅ is (C^-C₄ )alkyl , optionally substituted benzyl or allyl; (b) activation of the free carboxylic group of the compound obtained in step (a),

(c) reaction of the intermediate obtained on step (b) with a trialkyl phosphite P(OR₃' )₃, wherein R₃ ' has the above meanings, to give a keto-phoεphomc ester;

(d) reaction of the compound obtained m step (c) with a dialkyl silyl phosphite of formula (VII):

Si(R ) 63

.OR.

\ ³ (VII)

O P

OR •

wherein R₃' and R_β have the above meanings, followed by the hydrolysiε of the carboxylic ester group, to give the compounds of formula (VIII).

12. A procesε according to claim 11, wherein the R^ group is a benzyl group and wherein the hydrolysis of the step of the carboxylic group in step (d) lε performed by means of catalytic hydrogenation. 13 Procesε accordmg to claim 12, wherein the -Sι(Rg)₃ group is a tertbutyldimetylsilyl group.

14 Pharmaceutical compositions containing at least one compound according to claims 1-7 as active ingredient, together with pharmaceutically acceptable excipients. 15 The use of the compounds according to claims 1-7 as antitumor and anti-osteolytic agents. 16. The use according to claim 15, in which the tumors to be treated are multiple myeloma, osteosarcoma, bone metastaεiε, breaεt, ovary and teεtis carcinomas.