NOVEL METHYLENEBISPHOSPHONIC ACID DERIVATIVES

Abstract: Novel pharmaceutically active bisphosphonic acid derivatives of formula (I), in which R<1>, R<2>, R<3> and R<4> independently are C1-C22-alkyl, C2-C22-alkenyl, C2-C22-alkynyl, C3-C10-cycloalkyl, C3-C10-cycloalkenyl, aryl, aralkyl, silyl or hydrogen, whereby in the formula (I) at least one of the groups R<1>, R<2>, R<3> and R<4> is hydrogen and at least one of the groups R<1>, R<2>, R<3> and R<4> is different from hydrogen, Q<1> is hydrogen, fluorine, chlorine, bromine or iodine, and Q<2> is chlorine, bromine or iodine, including the stereoisomers, such as the geometrical isomers and optically active isomers, of the compounds, as well as the pharmaceutically acceptable salts of the compounds.

Description: Novel methylenebisphosphonic acid derivatives The invention concerns novel methylenebisphosphonic acid derivatives, in particular novel halogen substitu¬ ted methylenebisphosphonic ester acids and ester salts, as well as processes for the preparation of these novel compounds as well as pharmaceutical compositions comprising such novel compounds. Several publications disclose methylenebisphosphonic acids, their salts or some tetraesters, but there are only a few disclosures of corresponding halogen substi¬ tuted tri-, di- and monoesters (partial esters). The US patent 4,478,763 (1984) discloses a new process for the preparation of unsymmetrical isopropyl esters of (mono- and difluoromethylene)bisphosphonic acids. As further publications disclosing fluorine substituted compounds, the following may be mentioned: J. Org. Chem. , 51, (1986), 4788, J. Am. Chem. Soc, (1987) 5542, and Bioorg. Chem., (1988) 111. Thus the properties of the novel partial esters of (halogenmethylene)bisphosphonic acids and their salts according to the invention nor their use as medicaments, have not earlier been in¬ vestigated. According to the invention it has now been discovered that the novel partial esters of methylenebisphosphonic acids and their salts in many cases exhibit more favou¬ rable properties than the corresponding bisphosphonic acids and their salts due to their better kinetics and availability, their ability to participate as complex formers in the regulation of the metabolism of the or¬ ganism being maintained. In addition they are well suited for the treatment of disorders relating to the metabolism of calcium and of other, especially bivalent metals. They may be used for the treatment of diseases in the skeletal system, especially of bone formation and resorption disorders, such as of osteoporosis and Paget's disease, as well as for the treatment of diseases in the soft tissues, such as of deposition and mineralisation conditions and bone formation disorders. The novel bisphosphonates regulate either directly or over an indirect mechanism the level of cations freely present in the body fluids as well as of that binding to, active in and liberated from the tissues. Thus they are able to regulate the cellular metabolism, growth and destruction. Consequently they are useful for the treatment of e.g. cancer of the bone and metastases thereof, ectopic calcifications, urolithiasis, rheuma¬ toid arthritis, bone infections and bone degradation. The invention concerns novel methylenebisphosphonic acid derivatives of the general formula I in which formula R 1 , R 2 , R 3 and R 4 independently are C 2 -C 22 -alkenyl, C 2 -C 22 -alkynyl, C 3 -C 10 -cycloal yl, C 3 -C 10 -cycloalkenyl, aryl, aralkyl, silyl or hydrogen, whereby in the formula I at least one of the groups R 1 , R 2 , R 3 and R 4 is hydrogen and at least one of the groups R 1 , R 2 , R 3 and R 4 is different from hydrogen, Q 1 is hydrogen, fluorine, chlorine, bromine or iodine, and Q 2 is chlorine, bromine or iodine, including the stereo¬ isomers, such as the geometrical isomers and the opti- cally active isomers, of the compounds, as well as the pharmaceutically acceptable salts of the compounds. C 1 -C 22 -alkyl is straight or branched, preferably lower alkyl with 1 to 7 C-atoms, preferably 1 to 4 C-atoms, such as methyl, ethyl, propyl, isopropyl, or butyl, i-butyl, s-butyl or t-butyl, or pentyl, hexyl or heptyl, whereby preferably at least two, but more preferably three of the groups R 1 , R 2 , R 3 and R 4 are hydrogen, or it is C 8 -C 22 -alkyl, whereby preferably at least two, but more preferably three of the groups R 1 , R , R 3 and R 4 are hydrogen. Long chain is preferably a straight or branched C 1 -C 18 -alkyl group. C 2 -C 22 -alkenyl may also be straight or branched, and is preferably lower alkenyl with 2 to 7 C-atoms, prefe¬ rably 2 to 4 C-atoms, and has the meaning of ethenyl, 1-methyl-ethenyl, 1-propenyl, allyl or butenyl, 2-methyl-2-propenyl or also pentenyl, isopentenyl, 3-methyl-2-butenyl, hexenyl or heptenyl, whereby prefe¬ rably at least two, but more preferably three of the groups R 1 , R 2 , R 3 and R 4 are hydrogen, or it is C 8 -C 22 -alkenyl, whereby preferably at least two, but more preferably three of the groups R 1 , R 2 , R 3 and R 4 are hydrogen. Higher alkenyl is preferably a straight or branched C 14 -C 18 -alkenyl group. The said alkenyl groups may be either in E- or Z-form, or they may be conjugated or unconjugated dienyls, such as 3,7-dimethyl-2,6-octadiene, trienyls, such as farnesyl or polyenyls. C 2 -C 22 -alkynyl may also be straight or branched, and is preferably lower alkynyl with 2 to 7 C-atoms, prefer¬ ably 2 to 4 C-atoms, and means ethynyl, 1-propynyl, propargyl, or butynyl, or also pentynyl, hexynyl or heptynyl, whereby preferably at least two, but more preferably three of the groups R 1 , R 2 , R 3 and R 4 are hydrogen, or it is also C 8 -C 22 -alkynyl, whereby prefer¬ ably at least two, but more preferably three of the groups R 1 , R 2 , R 3 and R 4 are hydrogen. Higher alkynyl is preferably a straight or branched C 14 -C 18 -alkynyl group. Also conjugated or unconjugated di-, tri- and poly-ynyl and alkenynyl groups come into question. Cycloalkyl and -alkenyl contain 3 to 10 C-atoms and they may be substituted or unsubstituted, especially mono- or bicyclic, being preferably unsubstituted cyclopropyl, -butyl, -pentyl, -hexyl or -heptyl or bicyclo[3.2.0]- or -[2.2.1]heptyl, -[4.2.0]- or [3.2.1]octyl, -[3.3.1]nonyl, or the corresponding spiro-hydrocarbon residue, as well as the corresponding cycloalkenyl group or unsaturated spiro structure, or it may be polycyclic, such as adamantyl. As possible substituents, both in cis- and trans- isomers, for example C 1 -C 4 -alkyl and -alkenyl come into question. Aryl means a substituted or unsubstituted carbocyclic aromatic ring, such as phenyl, or a poly-, especially bicyclic, conjugated or bridged unsaturated or partly saturated ring system, such as naphtyl, phenanthryl, indenyl, indanyl, tetrahydronaphtyl, biphenyl, di- and triphenylmethyl etc. Aralkyl may be illustrated by the following formula wherein the groups A mean independently C 1 -C 4 -alkyl, halogen or nitro, q is an integer from 0 to 3, n is an integer from 0 to 6, and B is a straight or branched C j^ -Cg-alkyl group or a conjugated or uncon- jugated C 2 -Cg-alkenyl or -alkynyl group. In the silyl group (SiR 3 ) the group R is lower alkyl containing 1 to 4 C-atoms, and is especially methyl, ethyl, isopropyl, butyl, t-butyl, or it is phenyl or R- substituted phenyl, whereby also different combinations of lower alkyl and phenyl groups come into question, such as in dimethyl t-butyl-, methyl di-isopropyl-, dimethyl- and diethyl phenyl-, methyl t-butyl phenyl-, di-isopropyl-(2,6-dimethyl phenyl)-, dimethyl-(2,4,6- tri-isopropyl phenyl)silyl. The salts of the compounds of the formula I are especi¬ ally their salts with pharmaceutically acceptable ba¬ ses, such as metal salts, for example alkalimetal salts, especially litium, sodium and potassium salts, alkaline earth metal salts, such as calcium or magne¬ sium salts, copper, aluminium or zinc salts, as well as ammonium salts with ammonia or with primary, secondary and tertiary, both aliphatic and alicyclic and aromatic amines, as well as quaternary ammonium salts, such as halides, sulphates and hydroxides, salts with aminoal- cohols, such as ethanol-, diethanol- and triethanol- amines, tris(hydroxymethyl)aminomethane, 1- and 2-methyl and 1,1-, 1,2- and 2,2-dimethylaminoethanols, N-mono- and N,N-dialkylaminoethanols, N-(hydroxymethyl- and ethyl)-N,N-ethanediamines, as well as amino crown ethers and cryptates, and heterocyclic ammonium salts, such as azetidinium, pyrrolidinium, piperidinium, piperazinium, morpholinium, pyrrolium, imidazolium, pyridinium, pyrimidinium, quinolinium, etc., salts. An advantageous subgroup of the compounds of the for¬ mula I comprises the mono-, di- and triesters of the formula I, wherein Q 1 = Q = chlorine, and R 1 to R 4 are lower alkyl, especially methyl and ethyl. Another advantageous subgroup comprises the compounds of the formula I, wherein Q 1 = Q 2 = chlorine and one or two of the groups R 1 to R 4 are C 14 -C 18 -alkyl or -alkenyl. Especially advantageous compounds according to the in¬ vention are the monomethyl- and monoethylesters of (dichloro-, fluorochloro-, bromochloro-, and dibromomethylene)bisphosphonic acids. An especially advantageous compound is the monomethyl- and monoethylester of (dichloromethylene)bisphosphonic acid. The invention concerns also a process for the prepara¬ tion of the compounds of the formula I. The characte¬ ristic features of the processes are disclosed in the appended claims. According to one process the compounds are prepared by selective hydrolysis of the tetraesters corresponding to the formula I. Thus a tetraester II is used as the starting material, wherein the groups R 1 -R 4 (not hydro¬ gen) and Q 1 and Q 2 have the same meaning as in the for¬ mula I and this tetraester is hydrolyzed stepwise ac¬ cording to the following Scheme 1 to the triester III, diester IV and V and the monoester VI (the reaction takes place in the direction of the upper arrow) . If necessary, the partial ester III to VI or its salt may be isolated and purified by extraction, fractional crystallization or chromatographically, and if desired, a free acid may be converted into a salt or a salt into the free acid. tl tl • rg rg /\ /\ o o o o /\ /\ o o o o EC W SC TO aα ro o w t! ,/\ /\ /\ /\ o o o o o o o o X sc a x 33 X κ» W The hydrolysis of the tetraesters of the formula II may be carried out by treating with both an acid and a base, using thermal cleaving, and in certain cases also using water, an alcohol, an amide or other neutral or non- neutral transalkylation, -silylation and -arylation rea¬ gents. The hydrolysis takes place advantageously at a temperature range of 20 to 150 °C, generally from about 50 "C to the boiling point of the mixture. The acids are advantageously conventional inorganic acids, such as hydrochloric acid, sulphuric acid, phosphoric acid, and Lewis acids, such as borotrifluoride etherate, ti¬ tanium tetrachloride, etc. , as well as a number of or¬ ganic acids, such as oxalic acid, formic acid, acetic acid and other carboxylic acids, methanesulphonic acid and other sulphonic acids, such as P-toluene sulphonic acid, further chlorine and fluorine substituted carboxylic and sulphonic acids, such as trichloroacetic acid and trifluoromethane sulphonic acid, and their aqueous solutions. The bases are advantageously alkali and ammoniumhydro- xides and ammonia and the aqueous solutions thereof, as well as a number of amines, such as primary, secondary and tertiary amines, such as diethyl, triethyl, di- isopropyl and tributyl amine, aniline, and N- and N,N-alkyl substituted anilines and heterocyclic amines, such as pyridine, morpholine, piperidine, piperazine etc., and hydrazines, such as N,N-dimethyl hydrazine. In addition, acids and bases bound to a solid substrate may be used, such as Amberlites, either in the presence of an organic solvent or water or various solvent mixtures, or in the absence thereof. Further by treating with certain alkalimetals, such as sodium and litium, or with suitable inorganic salts, such as with sodium iodide, litium bromide, ammonium chloride and NaBr/PTC, the ester group may be converted directly to its corresponding salt, such as to the so¬ dium, ammonium and litium phosphonates. Thermal cleaving usually takes place at a temperature of about 100 to 400 °C, usually, however, at a tempera¬ ture of not more than 250 °C. The presence of a suit¬ able catalyst, such as an acid or an acid solution, or a quaternary ammonium salt, makes it possible to per¬ form the reaction faster and at a lower temperature. Some active substituents, such as benzyl and allyl, may be removed by catalytic reduction or electrolytically. To improve solubility and to control the reaction tem¬ perature during the reactions, organic, inert solvents, such as lower alcohols and stable ketones and esters, alkyl halides, such as chloroform or 1,2-dichloro- ethane, ethers, such as dioxan, dimethoxyethane, diglyme, etc., may be used as co-solvents. When all the ester groups R 1 -R 4 in the tetraester ac¬ cording to the formula II are the same, the hydrolysis takes place stepwise according to the Scheme 1, and it is interrupted when the concentration of the desired partial ester is at its greatest. In order to prepare a specific partial ester structure, it is advantageous to use a tetraester of the formula II wherein the ester groups are not the same (mixed tetraester), but contains groups which behave diffe¬ rently with respect to hydrolysis. It has, for example, been discovered that the hydrolysis rate of alkyl and silyl esters is dependant on the structure as follows: silyl > tert > sec > prim It is possible to fine tune the stepwise progress of the hydrolysis reaction also by means of the size and shape of the alkyl and silyl substituent as well as by electronical factors. In some instances advantage may be taken of a partial ester which is thermodynamically more favoured, for example, due to the formation of a chelate. It is often advantageous to perform a re- esterification in order to change or improve the step¬ wise hydrolysis of the different ester sites. Especial¬ ly the methylester may be converted to the correspond¬ ing acid over a silyl ester. Pure partial esters may thus be prepared in an advanta¬ geous manner by performing a selective hydrolysis, if necessary stepwise, of a mixed tetraester of the formu¬ la II, which has been prepared using ester groups which are advantageous from the point of view of hydrolysis, or corresponding unhalogenated compounds, whereby the halogenation may be carried out after the hydrolysis. Also selective hydrolysis reactions known especially from phosphate and monophosphonate chemistry may be used. The progress of the hydrolysis may be followed for example chromatographically or by means of 31 P-NMR and the reaction may be interrupted when the level of the desired partial ester is at its greatest and this may be isolated from the reaction mixture either as the free acid or as a salt by precipitation, extraction or chroma¬ tographically, and the salt form may be converted to the free acid or the free acid to its salt. The compounds according to this invention may be prepa¬ red also by selective esterification of bisphosphonic acids in accordance with the above mentioned reaction Scheme 1 (the reaction takes place in the direction of the lower arrow) . As a starting material a (halogenmethylene) bisphos¬ phonic acid according to the formula VII, or an un- halogenated bisphosphonic acid, which optionally is in the form of a salt, such as a metal or ammonium salt, or advantageously the corresponding phosphonic acid tetrachlorides are used, and depending on the desired end result, 1 to 4 equivalents of the desired aliphatic or aromatic alcohol, or the corresponding activated al- kylation, silylation and arylation reagents, such as orto-, imido- and vinylesters, ketene acetals and other suitable transfer reagents for alkyl-, silyl- and aryl groups, such as diazo compounds, active carboxylic acid esters, phosphates, phosphonates, phosphites, sulpha¬ tes, and sulphonates. The reaction is preferably per¬ formed under anhydrous conditions, preferably in the temperature range of 0 to 150 °C, or when using an inert co-solvent, at the boiling point thereof. The esters II to IV may also be prepared in a nucleo- philic substitution reaction between the bisphosphonate anion, often the ammonium salt of bisphosphonic acid, and an organic halide or sulphonate, or in a reaction of an other reagent, such as of amidates, for example halogen acetamidate, further in a condensation reaction between a phosphonic acid group and alcohols or a phe¬ nols corresponding to the desired groups R 1 -R 4 , using a reagent for cleaving off water, such as carbodi-imides and carbonyl- and sulphonylazoles, alkyl- or arylsul- phonyl chlorides, such as TPS, or oxidative esterfica- tion, such as phosphine + azodicarboxylic ester. Pure partial esters, also mixed esters, may thus be pre¬ pared in an advantageous manner by selective esterifica- tion, if necessary stepwise, of halogenated bisphosphonic acids of the formula VII, or of corresponding unha- logenated, whereby the halogenation may be carried out after the esterification. Also other selective esterification reactions may be used known primarily from phosphate and monophosphonate chemistry. The progress of the esterification reactions may be followed, for example, chromatographically or using 31 P-NMR and the reaction is interrupted when the con¬ tent of the desired partial ester is at its greatest and this is isolated from the reaction mixture by precipitation, extraction or chromatographically and, if desired, a salt form obtained is converted to the free acid or the free acid is converted to its salt. Partial esters of bisphosphonic acid according to the invention may also be prepared by constructing the P-C-P frame from its parts O 0R J R 3 0 base y-CQ 1 Q 2 -P P-Z > I OR 2 R 0 IX X wherein in the formula Y is hydrogen or halogen or ot¬ her leaving group, Z is halogen, aryloxy, sulphonyloxy or alkoxy, and R 1 - R 4 and Q 1 , Q 2 have the meaning gi¬ ven above, whereby Q2 may also have the meaning of hydrogen. The base is for example NaH, BuLi, or LDA. When Q 2 is hydrogen, the halogenation is carried out after preparation of the frame. In the starting material optionally present free acid sites (R 1 , R , R 3 or R 4 = H) have to be neutralized, by using a sufficient amount of base, prior to the coupling reaction. The coupling re¬ action and the halogenation may be carried out in the same vessel as consecutive steps taking advantage of the aleady existing anionic site at the carbon. Also the Michaelis-Arbuzov reactions may be used, whereby the compound of the formula X above is replaced by the corresponding phosphite, or the Michaelis-Becker reaction, whereby Z is hydrogen (cf. below). The partial esters of bisphosphonic acids according to the invention may also be prepared from P-C-P-compounds at a lower oxidation level by oxidation (for example p 111 XIII whereby in the formulas R 1 - R 4 and Q 1 , Q 2 have the me¬ aning given above, whereby the phosphonite structure may exist in an equilibrium with the hydrogenphosphona- te structure. . OH O / LI. -R -PH \ I OR OR All conventional oxidation agents, or their solutions, such as hydrogen peroxide, perhalogen compounds, per acids, permanganate etc., come into question. The partial esters of bisphosphonic acid according to the invention may also be prepared by halogenating the corres¬ ponding unhaiogenated partial esters, also stepwise, or the halogen(s) may be replaced by others, or one out of two may be removed. 0 0 0 0 0 0 R x 0-P-CH 2 -P-0R 4 R 1 0-P-CHQ -P-0R 4 R 1 0-P-CQ 1 Q 2 -P-OR 4 OR 2 OR 3 OR 2 OR 3 OR 2 OR 3 XV I (Q 1 .. H) I In the formulas R 1 - R 4 and Q 1 , Q 2 have the meaning given above, whereby in the exchange reactions Q 2 may also have the meaning of fluorine. The halogenation ta¬ kes place as will be described below, when one or more of the groups R 1 to R 4 is hydrogen, base has to be added in an amount sufficient to neutralize the free acid si¬ tes, as has been described above. The partial esters of bisphosphonic acids according to the invention may be prepared also using stepwise the above mentioned processes known primarily from phospha¬ te and monophosphonate chemistry. Also other selective reactions known primarily from phosphate and monophosphonate chemistry may be used. The partial esters I of bisphosphonic acid according to the invention may also be prepared from other partial esters VIII by performing an intra- or intermolecular exchange reaction / OR1 Q 1 / OR 2 > I Q 2/ \ OR 3 VIII ( VIII ≠ I ) in which formula VIII R 1 - R 4 and Q 1 , Q 2 have the mea¬ ning given above. Also the above mentioned reactions may be followed eg. chromatographically or using 31 P-NMR and interrupted when the content of the desired product is at its grea¬ test, this product being isolated from the reaction mixture as the free acid or as its salt by precipitati¬ on, extraction or chromatographically, and if desired, the salt form is converted to the free acid or the free acid to its salt. The tetraesters II and corresponding tetraacids IV used as starting materials in the above reactions may be prepared by processes known as such by constructing the P-C-P frame from its parts. Irrespective of the final partial ester, it is often advantageous to first prepare the tetraester according to the formula II using ester structures which are advantageous with re¬ spect to the preparation of the desired partial ester. In some cases, when preparing the biphosphonate frame, partial esters, especially symmetrical diester salts may be formed due to an immediate partial hydrolysis taking place under the reaction conditions. The bisphosphonate frame may be prepared, for example, using the following known reactions: a) The Michaelis-Becker reaction 0 OR 1 R 3 0 0 base R 3 0 0 O OR 1 γ-cQ ςr-p + P -H > P-CQ-'-CΓ-P OR 2 R 4 0 R 0 OR 2 IX X II In the formulas R 1 -R 4 , and Q 1 , Q 2 have the meaning given above, whereby also Q 2 may be hydrogen, and Y is halo¬ gen, acyloxy or sulphonyloxy. The base is Na, NaH, Bu- Li, LDA or KO-t-Bu/PTC. b) The Michaelis-Arbuzov reaction IX XI II In the formulas R-^-R 4 and Q 1 , Q 2 have the same meaning as above, whereby also Q 2 may be hydrogen, Y is halo¬ gen, acyloxy or sulphonyloxy, and Z 1 is alkoxy, silylo- xy, acyloxy or sulphonyloxy. c) The carbanion reaction Y' IX XII II In the formulas R 1 -R 4 and Q 1 , Q 2 have the same meaning as in the formula II, whereby also Q 2 may be hydrogen, Y' is hydrogen or halogen, Z" is halogen, alkoxy, acyl¬ oxy or sulphonyloxy. The base is BuLi, LDA, AlkMgHal or Alk 2 CuLi. Taking into account the preparation of the desired partial ester the above prepared tetraesters II may, if necessary, be converted to other suitable tetraesters using exchange reactions. Thereby the groups OR 1 - OR 4 may be exchanged directly or over the corresponding phosphonochloride (cf. above) or by applying other pro¬ cesses known primarily from phosphate and monophospho¬ nate chemistry (cf. above) . Halogen atom(s) may be substituted for the hydrogens on the carbon between the phosphorous atoms in the bisphosphonate advantageously also in the form of the tetraester II, whereby the reaction advantageously is performed using a hypohalite. Also other conventio¬ nal halogenation reactions come into question, such as the reactions of bisphosphono carbanions prepared using a strong base, with elemental halogens, or halogenation with N-haloamines and other active halides or polyhalo- gen compounds. It is, however, to be noted that contrary to what has been stated in the publication Zh. Obshch. Khim. 39 (1969) 845 - 8, the chlorination of the intermediate carbon with phosphorous pentachloride does not succeed (cf. eg. J. Chem. Soc. (1966) 757, cf also Example 14). In the first mentioned publication is namely stated that the treatment of methylenebis¬ phosphonic acid tetracyclohexyl ester with phosphorous pentachloride results in the symmetric (dichloro- methylene)bisphosphonic acid dicyclohexyl ester. It seems, however, that this is a wrong conclusion based on an impure composition. The halogen substituents of the carbon may also be in¬ troduced into the bisphosphonate structure as the halo¬ genated monophosphonate IX, whereby Q 1 and/or Q 2 are halogens. The halogen on the carbon in the frame may al¬ so be substituted for hydrogen, usually by nucleophilic dehalogenation, or for a different halogen using known reactions. The mixed halogen compounds I may also be prepared by the stepwise use of the above mentioned halogenation or exchange reactions (cf. Phosphorus and Sulfur, 37 (1988) 1). Optically active partial esters I may be prepared best by using known optically active compounds, such as op¬ tically active alcohols, in the preparation of the abo¬ ve mentioned starting materials, intermediates and end products, or in the exchange reactions. Bisphosphonates inhibit osteoclastic bone resorption. They are characterized by a non-hydrolyzable P-C-P bond which targets the compounds onto bone. They inhibit both forma¬ tion and dissolution of the bone mineral (Fleisch, H. In: Peck WA, ed. Bone and Mineral Research, Amsterdam: Excerp- ta Medica, 1983:319 (Annual 1)). However, compounds which are good inhibitors of calcium phosphate crystallization, may cause as a side-effect an inhibition of mineralisati¬ on. In addition to their physicochemical interaction with cal¬ cium phosphate crystals, bisphosphonates also influence cellular metabolism (Shinoda H. et al., Calcif Tissue Int 1983; 35:87). The exact mechanism of inhibition of bone resorption has not yet been clarified. Moreover, the ef¬ fects seem to vary from one bisphosphonate to another. Bisphosphonates are absorbed, stored and excreted unalte¬ red. The intestinal absorption is usually below 5% of the oral dose. A remarkable part of the absorbed bisphosphona¬ te is localised in bone, the reminder being rapidly excre¬ ted in the urine. The half-life of circulating bisphospho¬ nates is short, the rate of entry into bone being fast. On the other hand, the half-life of the skeletal retention is long. One aim of the present invention is to introduce new bis¬ phosphonate derivatives which have lower affinity for bone to avoid side-effects without loosing activity for bone resorption inhibition. Simultaneously increasing their ab- sortion after oral administration could lead into better therapeutic agents for the treatment of bone diseases. The biological activity of compounds according to the in¬ vention for preventing bone resorption in vitro and in vi¬ vo has been measured, as well as the interaction of the compounds with bone mineral and their relative bioavaila- bility after oral dosing. It was found that they exhibited lower affinity for bone than the reference compound clod- ronate. Despite this they have restored their biological activity as indicated by in vitro and in vivo resorption assay. In addition, the compounds are better absorbed af¬ ter oral administration than clodronate. The partial esters of mono- or dihalogenated methylene- bisphopshonic acids may thus be used as pharmaceuticals as such, or as their pharmacologically acceptable salts, such as the alkali or ammonium salts. Such salts may be prepared by reacting the ester acids with the cor¬ responding inorganic or organic bases. Depending on the reaction conditions, the ester salts are formed direct¬ ly in the above mentioned reactions under the reaction conditions used for preparing the compounds of the for¬ mula I. The new compounds I according to this invention may be administered enterally or parenterally. All conventio¬ nal administration forms, such as tablets, capsules, granules, syrups, solutions and suspensions come into question. Also all adjuvants for manufacture, solubili¬ ty and administration of the preparation, as well as stabilizers, viscosity regulating and dispersion agents and buffers may be used. Such adjuvants include ia. tartrate and citrate buf¬ fers, alcohols, EDTA and other nontoxic complexing agents, solid and liquid polymers and other sterile substrates, starch, lactose, mannite, methylcellulose, talc, silicic acids, fatty acids, gelatine, agar-agar, calcium phosphate, magnesium stearate, animal and vege¬ table fats and, if desired, flavouring and sweetening agents. The dosage depends on several factors, for example on the manner of administration, species, age and indivi¬ dual condition. The daily doses are about 1 to 1000 mg, usually 10 to 200 mg per person, and they may be ad- minstered as a single dose or may be divided into seve¬ ral doses. In the following, examples of a typical capsule and a tablet are given: Capsule mg/caps. Active ingr. 100.0 mg Starch 20.0 mg Magn. stear. 1.0 mg Tablet Active ingr. 400.0 mg Microcryst. cell. 20.0 mg Lactose 67.0 mg Starch 10.0 mg Talc .0 mg Magn. stear. 1.0 mg For medicinal use also a parenterally administered pre¬ paration may be made, for example an infusion concent¬ rate or injection. In the infusion concentrate eg. sterile water, phosphate buffer, NaCl, NaOH or HC1 or other suitable known pharmaceutical adjuvants may be used, in the injections also suitable pharmaceutical preservatives. It is also possible to formulate a topical formulation administered in a suitable vehicle. The compounds in ester-acid form are liquid or waxy substances, usually soluble in organic solvents and in some instances in water. The ester salts are solid, crystalline or typically powdery substances which usually dissolve well in water, in some instances in organic solvents, and only a few structures being poor¬ ly soluble in all solvents. The compounds are very stable, also in their neutral solutions at room tempe¬ rature. The structure of the compounds may easily be verified with 1 H-, 13 C- and 31 P-NMR-spectroscopy and FAB- masspectrometry or when silylated with EI- masspectrometry. For concentration and impurity deter¬ minations 31 P-NMR-spectroscopy is very suitable. For polar compounds as such ion exchange and exclusion-HPLC may be used and for tetraesters and silylated ester acid derivatives GLC or GC/MS may be used. From the compounds sodium and other metals were determined sepa¬ rately as well as the possible crystal water content. From the amine salts, nitrogen was determined. The following examples illustrate the invention without limiting the same. Example 1 : Trihexyl (dichloromethylene)bisphosphonate and monoso- dium salt 29.1 g (0.05 moles) of tetrahexyl ( ichloromethylene)- bisphosphonate ( 31 P-NMR (CDC1 3 ): δ 8.85) and 290 ml of pyridine are refluxed for about 1 hour (the reaction is followed with 31 P-NMR) and the mixture is evaporated under a vacuum. The residue (trihexyl (dichloro¬ methylene)bisphosphonate N-hexyl pyridinium salt) is dissolved in 300 ml of toluene and the solution is washed with 2 x 100 ml of 1 N NaOH and 100 ml of water and dried (MgS0 4 ) and filtered. The filtrate is evapo¬ rated under a vacuum. The waxy evaporation residue is dissolved in 100 ml of CH 3 OH and the solution is trea¬ ted with activated carbon and filtered. The filtrate is evaporated to constant weight under a vacuum, whereby about 21 g (80 % of the theor.) of (dichloromethylene)- bisphosphonic acid trihexyl ester monosodium salt are obtained ( 31 P-NMR (D 2 0) : δ 13.06 (P), 5.18 (P 1 ), 2 J pp = 18.0 Hz), at a concentration of 95 % and wherefrom trihexyl (dichloromethylene)bisphosphonate may be libe¬ rated with acid treatment. I.a. the following methylenebisphosphonic acid triesters and corresponding sodium salts may be prepared in an analogous manner: From tetrabutyl (dichloromethylene)bisphosphonate: tributyl (dichloromethylene)bisphosphonate from tetrapentyl (dichloromethylene)bisphosphonate: tripentyl (dichloromethylene)bisphosphonate from tetraheptyl (dichloromethylene)bisphosphonate: triheptyl (dichloromethylene)bisphosphonate from tetrapropyl (dichloromethylene)bisphosphonate: tripropyl (dichloromethylene)bisphosphonate from tetraisopropyl (dichloromethylene)bisphosphonate: triisopropyl (dichloromethylene)bisphosphonate (monosodium salt) ( 31 P-NMR(D 2 0) : δ 11.87 (P), 5.19 (P 1 ) 2 Jp p = 17.3 Hz) from tetraethyl (dichloromethylene)bisphosphonate: (triethyl (dichloromethylene)bisphosphonate N-ethyl- pyridinium salt isolated as an intermediate ( 31 P-NMR (D 2 0): δ 12.47 (P) , 1.30 (P 1 ), 2 J pp = 17.5 Hz) triethyl (dichloromethylene)bisphosphonate (monosodium salt) ( 31 P-NMR (D 2 0): δ 13.47 (P), 5.58 (P 1 ), 2 J PP = 17.0 HZ) from tetrakis(l-methylbutyl) (dichloromethylene)- bisphosphonate: tris(l-methylbutyl) (dichloromethylene)bisphosphonate from tetrakis(l-ethylpropyl) (dichloromethylene)- bisphosphonate: tris(1-ethylpropyl) (dichloromethylene)bisphosphonate from tetracyclopentyl (dichloromethylene)bisphosphonate: tricyclopentyl (dichloromethylene)bisphosphonate from tetraallyl (dichloromethylene)bisphosphonate: triallyl (dichloromethylene)bisphosphonate from tetraphenyl (dichloromethylene)bisphosphonate: triphenyl (dichloromethylene)bisphosphonate from tetrabenzyl (dichloromethylene)bisphosphonate: tribenzyl (dichloromethylene)bisphosphonate from tetramethyl (dichloromethylene)bisphosphonate: trimethyl (dichloromethylene)bisphosphonate ( 31 P-NMR (CDC1 3 ): δ 16.46 (P), 3.42 ( -? ' ) , 2J pp = 19.6 Hz), (monosodium salt) ( 31 P-NMR (CDC1 3 ): δ 15.74 (P), 6.58 (P 1 ), 2 J PP = 17.0 Hz), (tributylammonium salt) ( 31 P-NMR (CDC1 3 ): δ 15.50 (P), 4.25 (P')/ 16.6 Hz) from tetra-(Z)-3-hexenyl (dichloromethylene)bisphosp¬ honate: tri-(Z)-3-hexenyl (dichloromethylene)bisphosphonate (N-(Z)-3-hexenyl pyridinium salt) ( 31 P-NMR (CDC1 3 ) δ 12.53 (P), 4.70 (P'), 2 Jp P = 17.5 Hz) from P,P-diethyl P 1 ,P'-diisopropyl (dichloromethylene)bisphosphonate: P,P-diisopropyl P'-ethyl (dichloromethylene)- bisphosphonate (N-ethyl pyridinium salt) ( 31 P-NMR (CDCI3): δ 11.81 (P), 5.95 (P'), 2 J pp = 16.6 Hz) from P,P-diisopropyl P 1 ,P'-dimethyl (dichloromethylene)- bisphosphonate: P,P-diisopropyl P'-methyl (dichloromethylene)- bisphosp¬ honate (tributylmethyl ammonium salt) ( 31 P-NMR (CDCl ): δ 11.12 (P), 4.85 ( -? ' ) , 17.3 Hz) from P,P-diisopropyl P' ,P'-dihexyl (dichloromethylene)- bisphosphonate: P,P-diisopropyl P'-hexyl (dichloromethylene)- bisphosphonate (N-hexyl pyridinium salt) ( 31 P-NMR (CDC1 3 ): δ 8.67 (P) , 6.57 (P 1 )/ 2 Jpp = 20.9 Hz) from tetra(3-chlorophenyl) (dichloromethylene)- bisphosphonate: tri(3-chlorophenyl) (dichloromethylene)- bisphosphonate from tetra(3-phenyl 2-propenyl) (dichloromethylene)- bisphosphonate: tri(3-phenyl 2-propenyl) (dichloromethylene)- bisphosphonate from tetra(2-butunyl) ( ichloromethylene)- bisphosphonate: tri(2-butynyl) (dichloromethylene) bisphosphonate from tetrahexyl (dibromomethylene)bisphosphonate: trihexyl ( ibromomethylene)bisphosphonate from tetraisopropyl (dibromomethylene)bisphosphonate: triisopropyl (dibromomethylene)bisphosphonate from tetracyclopentyl (dibromomethylene)bisphosphonate: tricyclopentyl (dibromomethylene)bisphosphonate from tetraethyl (monobromomethylene)bisphosphonate: triethyl (monobromomethylene)bisphosphonate from tetrahexyl (monobromomethylene)bisphosphonate: trihexyl (monobromomethylene)bisphosphonate from tetraisopropyl (monobromomethylene)bisphosphonate: triisopropyl (monobromomethylene)bisphosphonate from tetracyclopentyl (monobromomethylene)bisphosphonate: tricyclopentyl (monobromomethylene)bisphosphonate from tetraisopropyl (diiodomethylene)bisphosphonate: triisopropyl (diiodomethylene)bisphosphonate from tetraphenyl (diiodomethylene)bisphosphonate: triphenyl (diiodomethylene)bisphosphonate from tetraisopropyl (monoiodomethylene)bisphosphonate: triisopropyl (monoiodomethylene)bisphosphonate from tetraisopropyl (monochloromethylene)bisphosphonate: triisopropyl (monochloromethylene)bisphosphonate from tetracyclopentyl (monochloromethylene)bisphosphonate: tricyclopentyl (monochloromethylene)bisphosphonate. from tetraethyl (monochloromethylene)bisphosphonate: triethyl (monochloromethylene)bisphosphonate from tetrahexyl (monochloromethylene)bisphosphonate: trihexyl (monochloromethylene)bisphosphonate from tetracyclohexyl (monochloromethylene)- bisphosphonate: tricyclohexyl (monochloromethylene)bisphosphonate Tetrahexyl (dichloromethylene)bisphosphonate used as a starting material above may be prepared in the following manner: 17.6 g (0.1 moles) of methylenebisphosphonic acid and 253 g (0.8 moles) of trihexyl ortoformate are refluxed for 3 h and then distilled under a vacuum until the in¬ ner temperature is about 170 °C/1 mmHg. As the distil¬ lation residue, about 51 g (100 % of theor.) of tetra¬ hexyl methylenebisphosphonate ( 31 P-NMR (CDC1 3 ): δ 20.04) are obtained as a colourless oil, the concentra¬ tion of which is 90 %. 25.6 g (0.05 moles) of tetrahexyl methylenebisphos- phonate are added while stirring to 250 ml of a 10 % NaOCl-solution at 0 °C during about 30 minutes, where¬ after stirring is continued for 1 h at 0 β C and 2 h at room temperature. The mixture is extracted with 2 x 100 ml of toluene and the combined extracts are washed with 50 ml of IN NaOH and 2 x 50 ml of water and dried (MgS0 4 ) and filtered. The filtrate is evaporated under a vacuum whereby about 25 g (85 % of the theor.) of tetrahexyl (dichloromethylene)bisphosphonate are obtai¬ ned ( 31 P-NMR (CDC1 3 ): δ 8.85), having a concentration of 95 %. I.a. the following (dichloromethylene)bisphosphonic acid tetraesters may be prepared in an analogous manner: From tetrabutyl methylenebisphosphonate ( 31 P-NMR (CDC1 3 ): δ 20.30): tetrabutyl (dichloromethylene)bisphosphonate ( 31 P-NMR (CDC1 3 ): δ 8.86) from tetrapentyl methylenebisphosphonate ( 31 P-NMR (CDC1 3 ): δ 20.06): tetrapentyl (dichloromethylene)bisphosphonate ( 31 P-NMR (CDC1 3 ): δ 8.85) from tetraheptyl-methylenebisphosphonate ( 31 P-NMR (CDC1 3 ): δ 20.07): tetraheptyl (dichloromethylene)bisphosphonate ( 1 P-NMR (CDC1 3 ): δ 8.86) from tetrapropyl methylenebisphosphonate: tetrapropyl (dichloromethylene)bisphosphonate from tetraisopropyl methylenebisphosphonate ( 31 P-NMR (CDC1 3 ): δ 17.92): tetraisopropyl (dichloromethylene)bisphosphonate ( 31 P-NMR (CDC1 3 ): δ 7.21) from tetramethyl methylenebisphosphonate ( 31 P-NMR (CDC1 3 ): δ 23.27): tetramethyl (dichloromethylene)bisphosphonate ( 31 P-NMR ' (CDClg) : δ 10.88) from tetraethyl methylenebisphosphonate ( 31 P-NMR from tetrakis(1-methylbutyl) methylenebisphosphonate ( 31 P-NMR (CDCI3): δ 18.10 (m)): tetrakis(1-methylbutyl) (dichloromethylene)bisphosphonate ( 31 P-NMR (CDCI3): δ 7.69) f om tetrakis(l-ethylpropyl) methylenebisphosphonate ( 31 P-NMR (CDC1 3 ): δ 18.37): tetrakis(l-ethylpropyl) (dichloromethylene)bisphosphonate ( 31 P-NMR (CDCI3): δ 7.89) from tetracyclopentyl methylenebisphosphonate ( 31 P-NMR tetracyclopentyl (dichloromethylene)bisphosphonate ( 31 P- from tetraallyl methylenebisphosphonate ( 31 P-NMR tetraallyl (dichloromethylene)bisphosphonate ( 31 P-NMR from tetra-(Z)-3-hexenyl methylenebisphosphonate ( 31 P-NMR (CDCI3): δ 20.12): tetra-(Z)-3-hexenyl (dichloromethylene)bisphosphonate ( 31 P-NMR (CDCI3): δ 8.72 (m) ) from tetrakis(2-methyl-2-propenyl) methylenebisphos¬ phonate ( 31 P-NMR (CDCI3): δ 20.31): tetrakis(2-methyl-2-propenyl) (dichloromethylene)bis¬ phosphonate ( 31 P-NMR (CDCI3) : δ 9.06) from tetraphenyl methylenebisphosphonate: tetraphenyl (dichloromethylene)bisphosphonate from tetrabenzyl methylenebisphosphonate ( 31 P-NMR tetrabenzyl (dichloromethylene)bisphosphonate. Tetrahexyl (dibromomethylene)bisphophonate useful as a starting material may be prepared in the following man¬ ner. Into a sodium hypobromite solution, which has been prepared by introducing 8.4 g of bromine into 4.6 g of NaOH in 50 ml of water, are added dropwise while stirring 10.2 g (0.02 moles) of tetrahexyl methylenebisphosphonate during appr. 1 minutes at 0 to 5 β C. The mixture is stirred for one hour w le cooling and one hour at room temperature and is extracte with methylene chloride. The extract is washed with water and dried (MgS0 4 ) and filtered. The filtrate is evaporated under vacuum, whereby appr. 10.5 g (80 % of the theor.) of tetrahexyl (dibromomethylene)bisphosphonate are obtained ( 31 P-NMR (CDCI3): δ 8.98 ppm) as a colourless oil, at a con centration of 97 %. I.a. the following (dibromomethylene)bisphosphonic acid tet raesters may be prepared in an analogous manner: Tetramethyl (dibromomethylene)bisphosphonate tetraethyl (dibromomethylene)bisphosphonate tetraisopropyl (dibromomethylene)bisphosphonate tetracyclopentyl (dibromomethylene)bisphosphonate ( 31 P-NMR (CDCI3): δ 7.26) tetrabutyl (dibromomethylene)bisphosphonate tetrapentyl (dibromomethylene)bisphosphonate Tetrahexyl (monobromomethylene)bisphosphonate useful as a starting material may be prepared in the following manner: Into a solution containing 6.7 g (0.01 moles) of tetrahexyl (dibromomethylene)bisphosphonate in 70 ml of abs. ethanol, 2.5 g of SnCl 2 x 2H 0 in 100 ml of water are added while stirring at 0 β C. After the addition, the mixture is stirre for 15 minutes and extracted with chloroform and the extrac is dried (MgS0 4 ) and filtered. The filtrate is evaporated under a vacuum, whereby about 4.1 g (70 % of the theor. ) of tetrahexyl (monobromomethylene)bisphosponate ( 31 P-NMR (CDCI3): δ 13.83 ppm) are obtained as a colourless oil, at a concentration of 90 %. I.a. the following (monobromomethylene)bisphosphonic acid tetraesters may be prepared in an analogous manner: Tetramethyl (monobromomethylene)bisphosphonate tetraethyl (monobromomethylene)bisphosphonate tetraisopropyl (monobromomethylene)bisphosphonate tetracyclopentyl (monobromomethylene)bisphosphonate Tetraisopropyl (monoiodomethylene)bisphosphonate useful as starting material may be prepared in the following manner: To 17.2 g (0.05 moles) of tetraisopropyl methylenebisphos¬ phonate in 300 ml of a 10 % K 2 C0 3 -solution, is added dropwise while stirring during about 20 minutes a solu¬ tion, which contains 6.35 g of I 2 and 20 g of KI in 50 ml of water. After the addition the mixture is stirred for 2 h and the solution is extracted with x 150 ml of CH 2 Cl . The extracts are combined and washed with a saturated NaCl-solution and dried (MgS0 4 ) and filtered. The filtrate is evaporated under a vacuum, whereby a evaporation residue of about 20 g is obtained as an al¬ most colourless oil. According to 31 P-NMR, the product contains 44 % of tetraisopropyl (monoiodomethylene)- bisphosphonate ( 31 P-NMR (CDC1 3 : δ 14.17) and 56 % of the starting material. Tetraisopropyl (monochloromethylene)bisphosphonate useful a a starting material may be prepared in the following manner Into a solution containing 8.2 g (0.02 moles) of tetraiso¬ propyl (dichloromethylene)bisphosphonate in 70 ml of ethano 9.0 g of sodium sulphite in 250 ml of water are added while stirring during 15 minutes at 10 to 15 °C, whereafter the mixture is stirred for 1 h. The mixture is extracted with chloroform and the extract is dried (MgS0 4 ) and filtered. The filtrate is evaporated under a vacuum, whereby about 7. g (100 % of the theor. ) of tetraisopropyl (monochloro¬ methylene)bisphosphonate ( 31 P-NMR (CDC1 : δ 12.04 ppm) are obtained as a colourless oil, at a concentration of 98 %. I.a. the following (monochloromethylene)bisphosphonic acid tetraesters may be prepared in an analogous manner. Tetramethyl (monochloromethylene)bisphosphonate tetraethyl (monochloromethylene)bisphosphonate tetracyclopentyl (monochloromethylene)bisphosphonate tetracyclohexyl (monochloromethylene)bisphosphonate. Example 2: P,P'-Dihexyl (dichloromethylene)bisphosphonate bis(N- hexylpyridinium) and disodium salt 29.1 g (0.05 moles) of tetrahexyl (dichloromethylene)- bisphosphonate and 290 ml of pyridine are refluxed for 1 da and the mixture is evaporated under a vacuum, whereby (dichloromethylene)bisphosphonic acid P,P'-dihexyl ester bis(N-hexylpyridinium) salt is obtained. This is dissolved in 180 ml of toluene and to the solution is added - while stirring effectively - 125 ml of 2N NaOH. The gelatinous precipitate is separated by filtration and is washed with acetone and ethyl acetate and dried in a vacuum desiccator whereby about 11.5 g (50 % of the theor.) of (dichloro¬ methylene)bisphosphonic acid P,P'-dihexylester disodium sal ( 31 P-NMR (D 2 0) : δ 8.97) are obtained, at a concentration of 96%. The P,P'-dihexyl (dichloromethylene)bisphosphonate may be liberated from its salt by treatment with an acid. In place of pyridine also other amines may be used, such as he- terocyclic amines (morpholine, see Ex. 7), piperidine, piperazine, etc. ) or aliphatic, primary, secondary or tertiary amines (di-isopropyl amine, triethyl amine, anili¬ ne, etc. ) . I.a. the following symmetrical (dichloromethylene)-bisphos¬ phonic acid diesters and their diamine and disodium salts may be prepared in an analogous manner: From tetramethyl (dichloromethylene)bisphosphonate: P,P'-dimethyl (dichloromethylene)bisphosphonate (disodium salt) ( 31 P-NMR (D 2 0) : S 10.00) (dipiperidinium salt) ( 31 P-NMR (D 2 0) : δ 9.70) from tetraethyl (dichloromethylene)bisphosphonate: P,P'-diethyl (dichloromethylene)bisphosphonate ( 31 P-NMR (D 2 0): δ 9.22) (disodium salt), 8.86 (dipiperidinium salt), 7.04 (bis(N-ethyl pyridinium) salt) from tetrapropyl (dichloromethylene)bisphosphonate: P,P'-dipropyl(dichloromethylene)bisphosphonate from tetraisopropyl (dichloromethylene)bisphosphonate: P,P'-diisopropyl (dichloromethylene)bisphosphonate ( 31 P- NMR(D 2 0): δ 7.93 (acid) 8.26 (disodium salt), 7.83 (diammonium salt), 8.23 (dilitium salt)) from tetrabutyl (dichloromethylene)bisphosphonate: P,P'-dibutyl (dichloromethylene)bisphosphonate from tetrapentyl (dichloromethylene)bisphosphonate: P,P'-dipentyl (dichloromethylene)bisphosphonate from tetraheptyl (dichloromethylene)bisphosphonate: P,P*-diheptyl (dichloromethylene)bisphosphonate from tetracyclopentyl (dichloromethylene)bisphosphonate: P,P'-dicyclopentyl (dichloromethylene)bisphosphonate from tetraallyl (dichloromethylene)bisphosphonate: P, P 1 -diallyl (dichloromethylene)bisphosphonate from tetrakis(2-methyl-2-propenyl) (dichloromethylene)bisphosphonate: P,P'-bis(2-methyl-2-propenyl) (dichloromethylene)bis¬ phosphonate ( 31 P-NMR (D 2 0: δ 8.60 (dipiperidinium salt) from tetracyclohexyl (dichloromethylene)bisphosphonate: P,P*-dicyclohexyl (dichloromethylene)bisphosphonate from tetraphenyl (dichloromethylene)bisphosphonate: P,P'-diphenyl (dichloromethylene)bisphosphonate from tetrabenzyl (dichloromethylene)bisphosphonate: P,P ■ -dibenzyl ( ichloromethylene)bisphosphonate from P,P'-dimethyl P,P'-diethyl (dichloromethylene) bisphosphonate P-methyl P'-ethyl (dichloromethylene)bisphosphonate ( 31 P-NMR (CDC1 3 ): δ 10.03 (P), 8.74 (P 1 ), 2 J pp = 15.5 Hz (bis(N-methyl piperazinium salt)). Example 3: P,P-Dihexyl (dichloromethylene)bisphosphonate and its disodium salt 5.0 g (0.01 moles) of P,P-dihexyl P 1 ,P'-di-isopropyl (dichloromethylene)bisphosphonate is dissolved in 100 ml of toluene and to the solution 6.7 g (0.07 moles) of methane sulphonic acid are added and the solution is stirred while heating and the progress of hydrolysis is followed with 31 P-NMR. When the reaction has reached a suitable stage, th mixture is cooled to room temperature and the lower phase i separated. The toluene phase is washed with 10 ml of water and dried (MgS0 4 ) and evaporated to constant weight under a vacuum, whereby appr. 3.3 g (80 % of the theor.) of P,P-dihexyl (dichloromethylene)bisphosphonate ( 31 P-NMR (CDCI3): δ (P) 11.89 ppm, (P 1 ) 5.27 ppm, 2 J pp , 21.0 Hz), ar obtained, at a concentration of 95 %. 2.07 g (0.005 moles) of the above bisphosphonic acid is mi¬ xed with 25 ml of water and the pH of the mixture is adjus¬ ted to 9 - 10 with 1.0 N NaOH. The mixture is evaporated to dryness under a vacuum and the evaporation is repeated afte the addition of isopropanol. The residue is mixed with acetone-isopropanol (1:1) and the precipitate is filtered and dried. The yield is about 1.8 g (80 % of the theor.) of (dichloromethylene)bisphosphonic acid P,P-dihexylester diso dium salt, at a concentration of 97 %. I.a. the following unsymmetrical (dichloromethylene)- bisphosphonic acid diesters and corresponding sodium salts may be prepared in an analogous manner: from P,P-dibutyl P 1 ,P'-diisopropyl (dichloromethylene)-bis¬ phosphonate ( 31 P-NMR (CDCl 3 ): δ 9.02 (P), 7.17 (P 1 ), 2 J pp 23.0 Hz) ) : P,P-dibutyl (dichloromethylene)bisphosphonate from P,P-dipentyl P' ,P'-diisopropyl (dichloromethylene)bis¬ phosphonate: P,P-dipentyl (dichloromethylene)bisphosphonate from P,P-diheptyl P 1 ,P'-diisopropyl (dichloromethylene)bis¬ phosphonate: P,P-diheptyl (dichloromethylene)bisphosphonate from P,P-diethyl P' ,P'-ditert-butyl (dichloromethylene)- bisphosphonate: P,P-diethyl (dichloromethylene)bisphosphonate from P,P-di-4-methylphenyl P' ,P'-ditert-butyl (dichloro¬ methylene)bisphosphonate: P,P-di-4-methylphenyl (dichloromethylene)bisphosphonate from P-decyl P-propyl P' ,P'-ditert-butyl (dichloro¬ methylene)bisphosphonate: P-decyl P-propyl (dichloromethylene)bisphosphonate. By using an aqueous solution of the acid the following compounds may be prepared in an analogous manner: from P,P-diethyl P 1 ,P'-isopropyl (dichloromethylene)- bisphosphonate: P,P-diethyl P'-isopropyl (dichloromethylene)bisphosphonate ( 1 P-NMR (CDCl 3 ): δ 13.86 (P), 5.12 (P'), 2 J PP = 17.0 Hz) from P,P-diisopropyl P 1 ,P'-dihexyl (dichloromethylene)- bisphosphonate: P,P-dihexyl P'-isopropyl (dichloromethylene) bisphosphonate ( 31 P-NMR (CDCI3): 6 10.41 (P), 5.71 (P « ), 2 J pp = 21.0 Hz). P,P-Dihexyl P 1 ,P'-diisopropyl ( ichloromethylene)- bisphosphonate used as a starting material above may be pre pared in the following manner: To a THF-hexane solution of LDA (litium diisopropyl amide) which contains appr. 0.072 moles of LDA, are added while stirring (N 2 -atmosphere) at -78 °C 9.0 g (0.034 moles) of d hexylmethyl phosphonate in 10 ml of anhydrous TMF, whereaf¬ ter stirring is continued for 15 minutes. To the mixture ar added while stirring at -78 °C 7.2 g (0.036 moles) of di¬ isopropyl chlorophosphate in 10 ml of anhydrous TMF, where¬ after stirring is continued for 15 minutes at -78 β C and th mixture is allowed to warm to -50 °C. To the mixture is add 5 N HC1 to a pH of 5 to 6, whereafter the mixture is evapo¬ rated under a vacuum. The residue is extracted with 3 x 50 ml of CHCI3 and the combined extracts are washed with a 10 NaHC0 3 solution and water and is dried (MgS0 4 ) and evaporated. The residue is stirred into ether and filtered. The filtrate is evaporated to dryness under a vacuum, where by about 13 g (90 % of the theor.) of P,P-dihexyl P',P' di¬ isopropyl methylenebisphosphonate ( 31 PNMR (CDCI3): δ 20.13 (P), 17.84 (P 1 ), 2 J PP = 7.6 Hz) are obtained, at a concent¬ ration of 90 %. The same product is obtained with a yield o about 80 % in the above manner but substituting the dihexyl methyl phosphonate with 8.5 g (0.034 moles) of dihexyl hydrogen phosphonate and the diisopropyl chlorophosphate with 7.7 g (0.036 moles) of diisopropyl (chloromethyl) phosphonate. To a mixture containing 32.8 g of NaHC0 3 in 130 ml of a 5 % NaOCl solution, are added while stirring vigorously at 0 β C 10.7 g (0.025 moles) of P,P-dihexyl P' ,P'-diisopropyl met¬ hylenebisphosphonate during 15 minutes. After the addition the mixture is stirred for 2 h at 0 °C and 2 h at room temp rature and extracted with 2 x 100 ml of toluene. The combi¬ ned extracts are washed with 2 x 75 ml of water and dried (MgS0 4 ) and filtered. The filtrate is evaporated under a va cuum, whereby appr. 10 g (80 % of the theor.) of P,P-dihexy P' ,P'-diisopropyl (dichloromethylene)bisphosphonate ( 31 P-NMR (CDC1 3 ): δ 8.98 (P), 4.72 (P'), 2 J pp = 22.9 Hz) ar obtained as a colourless oil at a concentration of 90 %. An alternative method for the preparation of an unsym- metrical starting tetraester, P,P-diethyl P 1 ,P'-diisopropyl methylenebisphosphonate, is presented in the following. Step 1: To 134 g (0.5 moles) of methylene iodide are added while stirring at 160 °C (N 2 -atmosphere) 66 g (0.31 moles) of tri isopropyl phosphite during 30 minutes, simultaneously dis¬ tilling off liberated isopropyl iodide. After the addition stirring is continued for 40 min at 160 to 165 °C and the mixture is fractionated under vacuum. The yield is appr. 62 g (65 % of the theor.) of diisopropyl (iodomethyl)phos¬ phonate, b.p. 100 to 103 °C/4 mm ( 31 P-NMR (CDCI3): δ 18.54), at a concetration of 95 %. Step 2: To 30.6 g (0.1 moles) of diisopropyl (iodomethyl)- phosphonate are added gradually while stirring at 185 to 205 °C (N 2 -atmosphere) 83 g (0.5 moles) triethyl phosphite while the liberated ethyl iodide is distilled off. After th addition stirring is continued for 10 min at 210 °C and the mixture is cooled and fractionated under a vacuum. The yiel is appr. 12.5 g (40 % of the theor.) of P,P-diethyl P' ,P'-diisopropyl methylenebisphosphonate, b.p. 140 - 150 °C/2 mm ( 31 P-NMR (CDC1 3 ): δ 17.77 (P), 20.20 (P 1 ), 2 J pp = 7.4 Hz), at a concentration of 95 %. I.a. the following unsymmetrical (dichloromethylene)bis¬ phosphonic acid P,P,P' ,P'-tetraesters may be prepared in an analogous manner: from P,P-dimethyl P' ,P'-diethyl methylenebisphosphonate ( 31 P-NMR (CDCI3): δ 22.65 (P), 19.55 (P'), 2 J pp = 6.00 Hz) P,P-dimethyl P 1 ,P'-diethyl (dichloromethylene)bisphospho¬ nate ( 31 P-NMR (CDCI3): δ 11.17 (P), 8.45 (P'), 2 J pp = 23.] Hz) from P,P-dimethyl P' ,P'-diisopropyl methylenebisphosphonate ( 31 P-NMR (CDC1 3 ): δ 23.00 (P), 17.43 (P 1 ), 2 J pp = 7.1 Hz): P,P-dimethyl P' ,P'-diisopropyl (dichloromethylene)bis¬ phosphonate ( 31 P-NMR (CDC1 3 ): δ 11.56 (P), 6.79 (P 1 ), 2 J pp = 22.8 Hz) from P,P-Diethyl P 1 ,P'-diisopropyl methylenebisphosphonate ( 31 P-NMR (CDC1 3 ): 6 20.20 (P), 17.77 (P'), 2 J pp = 7.4 Hz) : P,P-Diethyl P 1 ,P'-diisopropyl (dichloromethylene)bis¬ phosphonate ( 31 P-NMR (CDC1 3 ): δ 9.16 (P), 7.16 (P 1 ), 2 J pp = 22.8 Hz) from P,P-diethyl P' ,P'-di-tert-butyl methylenebisphosponate ( 31 P-NMR (CDC1 3 ): δ 20.88 (P), 10.68 (P'), 2 J pp = 13.3 Hz): P,P-diethyl P' ,P'-di-tert-butyl (dichloromethylene)bis¬ phosphonate ( 31 P-NMR (CDCI3): δ 10.38 (P), -0.37 (P'), 2 J pp 19.0 Hz) from p,P-diphenyl P' ,P'-dibenzyl methylenebisphosphonate ( 31 P-NMR (CDCI3): δ 12.77 (P), 19.27 (P 1 ), 2 J pp = 9.0 Hz) : P,P-diphenyl P 1 ,P'-dibenzyl (dichloromethylene)bis¬ phosphonate ( 31 P-NMR (CDCI3): δ 0.43 (P), 8.87 (P 1 ), 2 J pp = 22.9 Hz) from P,P-dibutyl P' ,P'-diisopropyl methylenebisphosphonate ( 31 P-NMR (CDC1 3 ): δ 20.22 (P), 17.90 (P'), 2 J pp = 7.9 Hz): P,P-dibutyl P" ,P'-diisopropyl (dichloromethylene)bis¬ phosphonate ( 31 P-NMR (CDC1 3 ): δ 9.02 (P) , 7.17 (P 1 ), 2 J pp = 23.0 Hz) from P,P-dipentyl P' ,P'-diisopropyl methylenebisphosphona¬ te: P,P-dipentyl P' ,P'-diisopropyl (dichloromethylene)- bisphosphonate from P,P-diheptyl P' ,P'-diisopropyl methylenebisphosphona¬ te: P,P-diheptyl P* ,P'-diisopropyl (dichloromethylene)- bisphosphonate from P,P,P'-trimethyl P'-isopropyl methylenebisphosphona¬ te ( 31 P-NMR (CDC1 3 ): δ 22.82 (P), 17.64 (P'), 2 J pp = 6.3 Hz) : P,P,P'-trimethyl P'-isopropyl (dichloromethylene)bisphos¬ phonate ( 31 P-NMR (CDC1 3 ): 6 11.24 (P), 8.91 (P 1 ), 23.1 Hz) from P,P,P'-trimethyl P'-hexyl methylenebisphosphonate: P,P,P'-trimethyl P 1 -hexyl (dichloromethylene)bisphospho¬ nate from P,P,P'-trimethyl P'-octadecyl methylenebisphosphonate: P,P,P « -trimethyl P'-octadecyl (dichloromethylene)bis¬ phosphonate from P,P-diisopropyl P'-octadecyl P'-tert-butyl methylene¬ bisphosphonate ( 31 P-NMR (CDC1 3 ): δ 15.76 (P), 18.35 (P'), Jpp = 9.2 H ) : P,P-diisopropyl P'-octadecyl P'-tert-butyl (dichloro¬ methylene)bisphosphonate from P,P-dimethyl P' ,P'-diphenyl methylenebisphosphonate ( 31 P-NMR (CDC1 3 ): δ 20.95 (P), 12.84 (P 1 ), 2 J pp = 7.9 Hz): P,P-dimethyl P 1 ,P'-diphenyl (dichloromethylene)bisphospho¬ nate ( 31 P-NMR (CDC1 3 ): δ 10.37 (P) , 0.17 (P"), 2 J pp = 23.2 HZ) Example 4 : Monohexyl (dichloromethylene)bisphosphonate and its triso- dium salt 4.7 g (0.01 moles) of P-hexyl P-tert-butyl P' ,P'-diisopropyl (dichloromethylene)bisphosphonate (prepared by chlorinating according to the Example 1 P-hexyl P-tert-butyl P' ,P'-diisopropyl methylenebisphosponate prepared from hexyl tert-butyl chlorophosphate and diisopropyl methylphosphonate in accordance with the Example 3) are stirred with 30 ml of 2N hydrochloric acid for 1 to 2 h at about 80 β C (the progress of hydrolysis is followed with 31 P-NMR). After the reaction the mixture is evaporated to constant weight under a vacuum, whereby monohexyl (dichloromethylene)bis¬ phosphonate is obtained as an oily residue. The evaporation residue is dissolved in water and 5.0 ml of a 2 N NaOH solu¬ tion are added and evaporated to constant weight under a va¬ cuum. The solid residue is washed with ethanol and dried to constant weight. The yield is about 3.5 g (90 % of the theor.) of (dichloromethylene)bisphosphonic acid monohexyl ester trisodium salt ( 31 P-NMR (D 2 0) : δ 11.50 (P), 9.36 (P'), 2 Jpp = 15.7 Hz), at a concentration of 98 %. The group to be removed may in place of the tert-butyl, isopropyl etc group also be a methyl group, which then may be hydrolysed selectively for example over the silyl ester (cf. Example 10) . I.a. the following (dichloromethylene)bisphosphonic acid mo- noesters and corresponding sodium salts may be prepared in an analogous manner (also the corresponding tetraesters used as starting materials have been prepared in an analo¬ gous manner, cf. Examples 1 and 3): from P-propyl P-tert-butyl P' ,P'-diisopropyl (dichlorome¬ thylene)bisphosphonate: monopropyl (dichloromethylene)bisphosphonate from P-butyl P-tert-butyl P' ,P'-diisopropyl (dichlorometh¬ ylene)bisphosphonate monobutyl (dichloromethylene)bisphosphonate from P-pentyl P-tert-butyl P' ,P'-diisopropyl (dichlorome¬ thylene)bisphosphonate: monopentyl (dichloromethylene)bisphosphonate from P-heptyl P-tert-butyl P' ,P'-diisopropyl (dichlorome¬ thylene)bisphosphonate: monoheptyl (dichloromethylene)bisphosphonate from P-decyl P-tert-butyl P' ,P'-diisopropyl (dichlorometh¬ ylene)bisphosphonate: monodecyl (dichloromethylene)bisphosphonate from P-dodecyl P-tert-butyl P 1 ,P'-diisopropyl (dichlorome¬ thylene)bisphosphonate: monododecyl (dichloromethylene)bisphosphonate from P-octadecyl P-tert-butyl P' ,P'-diisopropyl (dichloro¬ methylene)bisphosphonate: mono-octadecyl (dichloromethylene)bisphosphonate from P-allyl P-tert-butyl P 1 ,P'-diisopropyl (dichlorometh¬ ylene)bisphosphonate: monoallyl (dichloromethylene)bisphosphonate from P-phenyl P-tert-butyl P 1 ,P'-diisopropyl (dichloromethylene)bisphosphonate: monophenyl (dichloromethylene)bisphosphonate from P-benzyl P-tert-butyl P' ,P'-diisopropyl (dichlorome¬ thylene)bisphosphonate: monobenzyl (dichloromethylene)bisphosphonate from P-cyclohexyl P-tert-butyl P' ,P'-diisopropyl (dichlo¬ romethylene)bisphosphonate: monocyclohexyl (dichloromethylene)bisphosphonate from P-phenyl-P-tert-butyl P' ,P'-diisopropyl (monochloromethylene)bisphosphonate: monophenyl (monochloromethylene)bisphosphonate from P-4-bromo-phenyl P-tert-butyl P' ,P'-diisopropyl (dichloromethylene)bisphosphonate: 4-bromo-phenyl (dichloromethylene)bisphosphonate. Example 5 : Tri-isopropyl (dichloromethylene)bisphosphonate and monosodium salt 413 g (1 mole) of tetraisopropyl (dichloromethylene)- bisphosphonate are mixed with 4.1 1 of water and the mixtur is stirred under reflux for 1.5 h and is evaporated to a vo lume of appr. 750 ml. The solution is made alkaline while cooling with a 50 % NaOH solution and is left to stand at room temperature for appr. 3 days and is filtered. The filtrate is diluted with 315 ml of ethanol and stirred for 16 h at room temperature. The mixture is filtered and the filtrate is evaporated to appr. 140 ml and left to stand fo 5 days at room temperature. The precipitate is filtered and washed with 3 x 25 ml of methanol and dried to constant weight at 50 β C. The yield is appr. 44 g (11 %) of (dichloromethylene)bisphosphonic acid triisopropylester mo¬ nosodium salt ( 31 P-NMR (CDC1 3 ): δ 11.87 (P), 5.19 (P') 2 J pp = 17.3 Hz FAB-MS: m/z 393/395/397 (M+H) ) , at a concentratio of 90 % and which by treatment with an acid may be converte to triisopropyl (dichloromethylene)bisphosphonate. Example 6: P,P'-Diisopropyl (dichloromethylene)bisphosphonate, mono- and disodium salt (step 1). Monoisopropyl (dichlorometh¬ ylene)bisphosphonate and tri-sodium salt (step 2) Step 1: 413 g (1 mole) of tetraisopropyl (dichloromethylene)- bisphosphonate are mixed with 4.1 1 of water and the mixtur is stirred under reflux for 4 h and evaporated to a volume of appr. 870 ml. The solution is made alkaline while coolin with a 30 % NaOH solution and left to stand at room tempera ture for appr. 3 days and filtered (the filtrate is collec¬ ted - see step 2). The precipitate is stirred for 2 h with 190 ml of a 5 N NaOH solution and the mixture is filtered. The precipitate is washed with 30 ml of ethanol and is the¬ reafter stirred in 190 ml of abs. ethanol. The mixture is filtered and the precipitate is washed with 70 ml of abs. ethanol and dried to constant weight at 100 °C. The yield i appr. 115 g (31 % of the theor.) of (dichloromethylene) bisphosphonic acid P,P'-diisopropylester disodium salt ( 31 P-NMR (D20): δ 8.26) FAB-MS: m/z 373/375/377 (M+H) ) , at concentration of 99.5 % and which with acid treatment may b converted to P,P'-diisopropyl (dichloromethylene)bis¬ phosphonate from which the corresponding monosodium salt ma be prepared by adding 1 equivalent of NaOH to the aqueous solution of the acid. Step 2: The filtrate obtained in the first filtration in the previ¬ ous step is evaporated to a volume of appr. 410 ml and is left to stand at room temperature for appr. i6 h. The preci pitate is filtered off and the pH of the filtrate is adjust a 8.5 with concentrated hydrochloric acid and a solution is added containing 95 ml of methanol and 63 ml of water and the mixture is stirred for 3 days at room temperature. The mixture is filtered and the precipitate washed with 30 ml o methanol and dried to constant weight at 100 °C. The yield is appr. 38 g (11 % of the theor.) of (dichloromethylene) bisphosphonic acid monoisopropyl ester trisodium salt ( 31 P-NMR (D 2 0): δ 10.95 (P), 9.54 (P*), 2 J pp = 16.6 Hz FAB- MS: m/z 353/355/357 (M+H)) at a concentration of 97 % and which with acid treatment may be converted to monoisopropyl (dichloromethylene)bisphosphonate. Example 7 : P,P'-diisopropyl (dichloromethylene)bisphosphonate and dimorpholinium salt 12.4 g (0.03 moles) of tetraisopropyl (dichloromethylene) bisphosphonate, 120 ml of morpholine and 60 ml of chloroform are stirred under reflux for 3 h and left to stand at appr. 4 °C for 1 day. The mixture is filtered and the precipitate is washed with 60 ml of chloroform and dried. The yield is appr. 12.5 g (83 % of the theor.) (dichloromethylene) bisphosphonic acid diisopropyl ester dimorpholinium salt ( 31 P-NMR (D 2 0): δ 7.86), at a concentration of 94 % and from which P,P'-diisopropyl (dichloromethylene)bisphosphonate may be liberated with acid treatment. When instead of morpholine other secondary amines are used, such as piperi- dine, dibutyl amine etc., the corresponding diamine salt, e.g. dipiperidinium and dibutylammonium salt of (dichloro¬ methylene)bisphosphonic acid P,P'-diisopropyl ester is obtained (cf. Example 2). The reaction may also be carried out in the absence of a co-solvent. I.a. the following symmetrical (dichloromethylene) bisphosphonic acid diester dimorpholinium salts may be pre¬ pared in an analogous manner: From tetraethyl (dichloromethylene)bisphosphonate: P,P'-diethyl (dichloromethylene)bisphosphonate ( 31 P-NMR (D 2 0): δ 8.88) from tetraisopropyl (dichloromethylene)bisphosphonate: P,P-diisopropyl (dichloromethylene)bisphosphonate ( 31 P-NMR (D 2 0): δ 7.86) from tetracyclopentyl (dichloromethylene)bisphosphonate: P,P'-dicyclopentyl (dichloromethylene)bisphosphonate ( 31 P-NMR (D 2 0): δ 8.38) from tetrakis ( 1-methylbutyl) (dichloromethylene) bis- phosphonate: P,P'-Bis(1-methylbutyl) (dichloromethylene)bisphosphonate ( 31 P-NMR (D 2 0): δ 8.24) from tetrakis(l-ethylpropyl) (dichloromethylene)bis¬ phosphonate: P,P'-bis(l-ethylpropyl) (dichloromethylene)bisphosphonate from P,P-diisopropyl P' ,P'-dimethyl (dichloromethylene)bis¬ phosphonate: P-isopropyl P'-methyl (dichloromethylene)bisphosphonate from tetra-(Z)-3-hexenyl (dichloromethylene) bisphosphonate P,P'-di-(Z)-3-hexenyl (dichloromethylene)bisphosphonate from P,P-diphenyl P' ,P'-dibenzyl (dichloromethylene) bisphosphonate P-phenyl P'-benzyl (dichloromethylene)phosphonate from P,P-diisopropyl P' ,P'-diethyl (dichloromethylene)bis¬ phosphonate: P-isopropyl P'-ethyl (dichloromethylene)bisphosphonate from P,P-diisopropyl P 1 ,P'-dibutyl (dichloromethylene)bis¬ phosphonate: P-isopropyl P'-butyl (dichloromethylene)bisphosphonate from P,P-diisopropyl P' ,P'-dihexyl (dichloromethylene)bis¬ phosphonate: P-isopropyl P'-hexyl (dichloromethylene)bisphosphonate ( 31 P-NMR (CDC1 3 ): δ 6.87 (P), 7.67 (P 1 ), 2 J pp = 20.4 Hz) from P,P,P'-triethyl P'-bicyclo[2.2.1]heptan-2-yl (dichloromethylene)bisphosphonate: P-bicyclo[2.2.1]heptan-2-yl P'-ethyl (dichloromethylene)- bisphosphonate from P,P,P'-triethyl P'-propargyl (dichloromethylene)bis¬ phosphonate: P-propargyl P'-ethyl (dichloromethylene)bisphosphonate from P,P,P'-triethyl P'-4-methoxyphenyl (dichloromethylene)- bisphosphonate: P-4-methoxyphenyl P'-ethyl (dichloromethylene)- bisphosphonate from P,P-diethyl P 1 ,P'-dimethyl (monochloromethylene)bis¬ phosphonate: P-ethyl P'-methyl (monochloromethylene)bisphosphonate (di¬ piperidinium salt) ( 31 P-NMR (D 2 0): δ 12.05 (P), 13.05 (P » ), 2.7 HZ) from tetraallyl (monochloromethylene)bisphosphonate: P,P'-diallyl (monochloromethylene)bisphosphonate from tetraallyl (dibromomethylene)bisphosphonate: P,P'-diallyl (dibromomethylene)bisphosphonate from tetrahexyl (dibromomethylene)bisphosphonate: P,P'-dihexyl (dibromomethylene)bisphosphonate ( 31 P-NMR (D 2 0): δ 11.92) from tetrahexyl (monobromomethylene)bisphosphonate P,P'-dihexyl (monobromomethylene)bisphosphonate ( 31 P-NMR (D 2 0): δ 8.44) from tetracyclopentyl (monobromomethylene)bisphosphonate: P,P'-dicyclopentyl (monobromomethylene)bisphosphonate (di¬ piperidinium salt) ( 31 P-NMR (D 2 0): δ 8.47) from tetraethyl (dibromomethylene)bisphosphonate: P,P'-diethyl (dibromomethylene)bisphosphonate from tetrabutyl (dibromomethylene)bisphosphonate: P,P'-dibutyl (dibromomethylene)bisphosphonate from tetrapentyl (dibromomethylene)bisphosphonate: P,P ■ -dipentyl (dibromomethylene)bisphosphonate from tetracyclopentyl (dibromomethylene)bisphosphonate: ( 31 P-NMR (D 2 0): δ 7.26) P,P'-dicyclopentyl (dibromomethylene)bisphosphonate. The used (halogenmethylene)bisphosphonic acid (mixed) tetra esters have been prepared according to the methods disclosed in the Examples 1 and 3. Example 8 : Tetramethyl (dichloromethylene)bisphosphonate and trimethyl (dichloromethylene)bisphosphonate 1.2 g (0.05 moles) of anhydrous finely divided (dichloro¬ methylene)bisphosphonic acid are stirred in 100 ml of anhyd¬ rous chloroform and into the mixture are added dropwise while stirring at 15 to 20 'C 53 ml of a 2 % ether solution of diazomethane. After the addition stirring is continued for 30 min at room temperature and the mixture is evaporated to constant weight under a vacuum. The yield is appr. 1.5 g (100 % of the theor.) of tetramethyl (dichloro¬ methylene)bisphosphonate ( 31 P-NMR (CDCI3): δ 10.88), at a concentration of 98 %. When mixing tetramethyl (dichloromethylene)bisphosphonate in aqueous ether for 3 h under reflux, pure trimethyl (dichloromethylene)bisphosphonate is obtained with a yield Of over 90 % ( 31 P-NMR (CDCI3): δ 16.46 (P), 3.42 (P'), 2 J pp 19.6 Hz) . Example 9: Monohexyl (dichloromethylene)bisphosphonate and trisodium salt 3.19 g (0.01 moles) of (dichloromethylene)bisphosphonyl tet- rachloride (distilled, b.p. 105 to 110 °C/1 mm) are dissolve in 30 ml of anhydrous toluene and to the solution are added dropwise while stirring at 0 to 5°C 1.02 g (0.01 moles) of 1-hexanol in 10 ml of anhydrous toluene. After the addition stirring is continued for 30 min at 0 to 5 β C and 1 h at appr. 25 °C and 10 ml of water is added dropwise and the mixture is stirred vigorously for 1 h at 30 to 40 °C. The solution is cooled to room temperature and the pH is a jus- ted to 10 to 11 with 2 N NaOH and evaporated to constant weight under a vacuum. The residue contains about 60 % of (dichloromethylene)bisphosphonic acid monohexyl ester triso- dium salt which can be purified by fractional crystallisati¬ on from water-methanol. The yield is appr. 1.8 g (45 % of the theor.) and concentration > 90 %. ( 31 P-NMR (D 2 0) : δ 11.50 (P), 9.36 (P'), 2 J pp = 15.7 Hz). Example 10: P,P-diisopropyl (dichloromethylene)bisphosphonate and diso¬ dium salt 7.4 g (0.02 moles) of P,P-diisopropyl-P' ,P'-dimethyl (dichloromethylene)bisphosphonate are dissolved in 75 ml of anhydrous acetonitrile and 6,0 g of sodium iodide are added as well as 22.4 g of chlorotrimethyl silane. The mixture is stirred for 15 min under reflux and evaporated under a va¬ cuum, whereby P,P-diisopropyl P' ,P'-bis(trimethylsilyl) (dichloromethylene)bisphosphonate ( 31 P-NMR (CDCl 3 ): δ 7.50 (P), -9.61, (P 1 ), 2 J PP = 24.3 Hz) is obtained. This is hyd- rolyzed by adding 25 ml of water of a temperature of appr. 50 β C, whereafter the solution is made alkaline with a 10 % NaOH solution and is evaporated to constant weight under a vacuum. The solid residue is mixed in 50 ml of acetone and is left standing in ice water for 4 h. The precipitate is filtered and washed with acetone and dried to constant weight at 70 β C. The yield is appr. 6.8 g (88 % of the theor.) of (dichloromethylene)bisphosphonic acid P,P-di- isopropyl ester disodium salt ( 31 P-NMR (D 2 0) : δ 14.52 (P), 7.20 (P')/ 2j pp = 16.0 Hz), at a concentration of 98 % and which with acid treatment may be converted to the cor¬ responding acid. I.a. the following (dichloromethylene)bisphosphonic acid si¬ lyl and partial esters may be prepared by analogous methods: from P,P-dimethyl P' ,P'-diethyl (dichloromethylene)bisphosphonate: P,P-bis(trimethylsilyl) P' ,P'-diethyl (dichloromethylene)bisphosphonate, wherefrom P' ,P'-diethyl (dichloromethylene)bisphosphonate ( 31 P-NMR (CDCI3): δ 16.67 (P), 7.20 (P 1 ), 2 J pp = 15.5 (sodium salt) ) from P,P,P'-trimethyl P'-hexyl (dichloromethylene)bisphospho nate: P,P,P'-tris(trimethylsilyl) P 1 -hexyl (dichloromethylene) bisphosphonate, wherefrom monohexyl (dichloromethylene)bisphosphonate ( 31 P-NMR (D 2 0): δ 11.50 (P), 9.36 (P'), 2 J pp = 15.74 Hz (trisodium salt) from P,P,P'-triisopropyl P'-methyl (dichloromethylene)bis¬ phosphonate: P,P,P'-triisopropyl P'-trimethylsilyl (dichloromethylene) bisphosphonate, wherefrom P,P,P'-triisopropyl (dichloromethylene)bisphosphonate ( 31 P-NMR (CDCI3): δ 11.87 (P), 5.19 (P' ) , 2 J pp = 17.2 Hz (monosodium salt) ) from P,P,P'-trimethyl P-isopropyl (dichloromethylene)bis¬ phosphonate: P,P,P'-tris(trimethylsilyl) P-isopropyl (dichloromethylene bisphosphonate ( 31 P-NMR (CDCI3): δ -1.18 (P), -9.71 (P 1 ), 2 J PP = 27.1 Hz), wherefrom monoisopropyl (dichloromethylene)bisphosphonate from P,P-diisopropyl P' ,P'-dimethyl (dichloromethylene)- bisphosphonate: P,P-diisopropyl P'-methyl P'-trimethylsilyl (dichloromethylene)bisphosphonate ( 31 P-NMR (CDCl 3 ): δ 7.81 (P), 1.12 (P'), 2 J pp = 23.3 Hz), wherefrom P,P-diisopropyl P'-methyl (dichloromethylene)bisphosphonate, from P,P,P'-trimethyl P'-octadecyl (dichloromethylene)bis¬ phosphonate: P,P,P'-tris(trimethylsilyl) P'-octadecyl (dichloro- methylene)bisphosphonate, wherefrom octadecyl (dichloromethylene)bisphosphonate and trisodium salt from P,P-dimethyl P' ,P'-diphenyl (dichloromethylene)bisphosphonate: P,P-bis(trimethylsilyl) P' ,P'-diphenyl (dichloromethylene) bisphosphonate ( 31 P-NMR (CDC1 3 ): δ -11.26 (P), 2.03 (P 1 ), 2 J PP = 26.6 Hz), wherefrom P,P-diphenyl (dichloromethylene)bisphosphonate ( 31 P-NMR ( 2 0): δ 6.48 (P) , 11.01 (P'), 2 J pp = 14.7 Hz (disodium salt)) from P,P,P'-trimethyl P'-(3-methyl-2-cyclohexenyl) (dichloromethylene)bisphosphonate P,P,P'-tris(trimethylsilyl) P'-(3-methyl-2-cyclohexenyl) (dichloromethylene)bisphosphonate, wherefrom (3-methyl-2-cyclohexenyl) (dichloromethylene) bisphosphonate ( 31 P-NMR (D 2 0): δ 9.25, 8.81 2 J pp = 17,6 Hz (trisodium salt)) from P,P'-diphenyl P,P'-dimethyl (dichloromethylene)- bisphosphonate: P,P'-bis(trimethylsilyl) P,P'-triphenyl (dichloro¬ methylene)bisphosphonate, wherefrom P,P'-diphenyl (dichloromethylene)bisphosphonate from P,P,P'-trimethyl P'-farnesyl (dichloromethylene)- bisphosphonate: P,P,P'-tris(trimethylsilyl) P'-farnesyl (dichloro¬ methylene)bisphosphonate, wherefrom monofarnesyl ( ichloromethylene)bisphosphonate from P,P,P-trimethyl P'-l-tetrahydronaphtyl (dichloro¬ methylene)bisphosphonate: P,P,P'-tris(trimethylsilyl) P'-1-tetrahydronaphtyl (dichloromethylene)bisphosphonate, wherefrom 1-tetrahydronaphtyl (dichloromethylene)bisphosphonate from P,P-diethyl P' ,P'-dimethyl {monochloromethylene)- bisphosphonate: P,P-diethyl P' ,P'-bis(trimethylsilyl) (monochloro- methylene)bisphosphonate, wherefrom P,P-diethyl (monochloromethylene)bisphosphonate from P,P,P'-trimethyl P*-1-octadecyl (dibromomethylene)- bisphosphonate: P,P,P'-tris(trimethylsilyl) P'-1-octadecyl (dibromo¬ methylene)bisphosphonate, wherefrom 1-octadecyl (dibromomethylene)bisphosphonate. In an analogous manner the following compounds may be prepared: from P,P-diethyl P' ,P'-dimethyl (dichloromethylene)- bisphosphonate: P,P-diethyl P' ,P'-bis(t-butyldimethylsilyl) (dichloromethylene)bisphosphonate, wherefrom P,P-diethyl P'-t-butyldimethylsilyl) (dichloro¬ methylene)bisphosphonate ( 31 P-NMR (CDCI3): δ 9.70 (P), -1.06 (P*), 2 J pp = 23.7 Hz) from tetraethyl (dichloromethylene)bisphosphonate: P,P'-diethyl P,P'-bis(t-butyldimethylsilyl) (dichloromethylene)bisphosphonate, wherefrom P,P'-diethyl P-t-butyldimethylsilyl (dichloromethylene) bisphosphonate ( 31 P-NMR (CDCI3): δ 7.05 (P), 0.68 (P*), 2 j pp = 23.4 Hz) . from tetramethyl (dichloromethylene)bisphosphonate: P-methyl P,P' ,P'-tris(t-butyldiphenylsilyl) (dichloro¬ methylene)bisphosphonate ( 31 P-NMR (CDCI3): δ 1.18 - 12.08 (P,P' ) , 35.9 Hz) Example 11 : P,P'-di-isopropyl (dichloromethylene)bisphosphonic acid monobarium, monocalcium, mono- and dipotassium, mono- and dilitium and mono- and diammonium salts 3.29 g (0.01 moles) of P,P'-diisopropyl (dichloro¬ methylene)bisphosphonic acid are dissolved in 22 ml of water and while stirring 3.15 g (0.01 moles) of Ba(OH) 2 x 8H 2 0 are added and stirring is continued for 2 h. The mixture is filtered and the filtrate is evaporated to constant weight under a vacuum. The yield is appr. 4.5 g (96 % of the theor.) of colourless crystalline P,P'-di- isopropyl (dichloromethylene)bisphosphonic acid monoba¬ rium salt at a concentration of > 98%. In an analogous manner i.a. the monocalcium salt, the mono- and dipotassium salt, the mono- and dilitium salt as well as the mono- and diammonium salt (yield > 95 %, concentration > 98 %) have been prepared. Example 12: P,P'-diisopropyl (monochloromethylene)bisphosponate and dimorpholinium salt 8.2 g (0.02 moles) of tetraisopropyl (dichloromethylene)bisphosphonate (prepared as has been described in the Example 1) in 80 ml of morpholi¬ ne are stirred under reflux for 24 h and the solution is cooled. The formed precipitate is separated and recrystallized from ether. The yield is appr. 8.5 g (90 % of the theor.) of colourless crystalline P,P'-diisopropyl (monochloromethylene)bisphosphonate ( 31 P-NMR (D 2 0): δ 11.31 ppm (dimorpholinium salt)) at a concentration of appr. 85 % (the product contains appr. 15 % of the corresponding dichloro compound) and wherefrom the corresponding acid mmay be liberated by treating an aqueous solution of the product with two equivalents of hydrochloric acid. I.a. the following (monochloromethylene)bisphosphonic acid diesters have been prepared in an analogous manner: P,P'-Diethyl (monochloromethylene)bisphosphonate ( 31 P-NMR (D 2 0): δ 12.40 ppm (dipiperidium salt)) P,P'-Dicyclopentyl (monochloromethylene)bisphosphonate ( 31 P-NMR (D 2 0) : δ 11.87 ppm (dipiperidinium salt). Example 13: Monoethyl (dichloromethylene)bisphosphonate and tri¬ sodium salt 5.0 g (0.014 moles) of tetraethyl (dichloromethylene)- bisphosphonate and 6.7 g (0.045 moles) of Nal are dissol¬ ved in 50 ml of anhydrous CH3CN and while stirring 12.2 g (0.112 moles) of trimethylsilyl chloride are added. After the addition stirring is continued at room temperature, protected from moisture, for appr. 4 days and is evapora¬ ted under a vacuum. To the mixture obtained as a residue (contains as the major component monoethyl tris(tri¬ methylsilyl) (dichloromethylene)bisphosphonate) 10 ml of water are added and the mixture is made alkaline with a 10 % NaOH solution. The mixture is diluted with 50 ml of CH3OH and is left standing at +4 °C for 2 h and is filte¬ red (the precipitate is (dichloromethylene)bisphosphonic acid sodium salt) . To the filtrate 25 ml of ethanol are added and it is left standing for 1 day at +4 °C and is filtered. The filtrate is evaporated under a vacuum and the residue is washed with acetone and filtered. The pre¬ cipitate is dried to constant weight whereby appr. 2.0 g (50 % of the theor.) of colourless crystalline (dichloromethylene)bisphosphonic acid monoethyl ester trisodium salt are obtained ( 31 P-NMR (D 2 0) : δ 11.86 (P), 9.40 (P') 2 J PP = 15.4 Hz) at a concentration of > 90 % and wherefrom the corresponding acid may be liberated with acid treatment. In an analogous manner monomethyl (dichloromethylene)- bisphosphonate and its trisodium salt ( 31 P-NMR (D 2 0) : δ 10.58 (P), 8.58 (P'), 2 J pp = 16.7 Hz) has been prepared from tetramethyl (dichloromethylene)bisphosphonate ; (disodiummonopiperidinium salt) 31 P-NMR (D 2 0) : δ 12.97 (P) , 9.17 (P' ), 15.1 Hz) . Example 14: Treatment of tetraisopropyl (methylene)bisphosphonate with phosphorous pentachloride 3.44 g (0.01 moles) of tetraisopropyl (methylene)bis¬ phosphonate were treated, while stirring, in portions with 4.16 g (0.02 moles) of PCl 5 , whereby the mixture war¬ med to appr. 50 β C. After the addition stirring was continued for 2 h and the clear solution was evapora¬ ted under a vacuum. To the residue were added while cooling 20 ml of water and after the termination of the exothermic reaction the mixture was stirred under reflux for 30 min and evaporated under a vacuum. The clear oil obtained as a residue was analysed using 31 p- and 1 H-NMR and the composition was found to be the following: δ 31 P-NMR (NaOD) mole % Methylenebisphosphonate 17.17 21.5 Monoisopropyl methylene bisphosphonate 19.94,14.74, 2 J pp =8.2 Hz 41 P,P'-diisopropylmethylene- bisphosphonate 17.24 20 Phosphate 3.33 15 Monoisopropylphosphate 3.62 2.5 There were no signs that the hydrogens on the interme¬ diate carbon had been exchanged to chlorine atoms. Example 15: Tetracyclopentyl (bromochloromethylene)bisphosphonate and P,P ^ -dicyclopentyl (bromochloromethylene)bisphosphonate and its dipiperidinium salt 4.8 g (0.01 moles) of tetracyclopentyl (monochloro¬ methylene)bisphosphonate ( 31 P-NMR (CDC1 3 ): δ 12.44 ppm, 2 J pH = 17.7 Hz) are dissolved in 20 ml of carbontetrachlo- ride and 0.55 g of bensyltriethylamnmonium chloride and 20 ml of a 10% sodium hypobromite solution are added while cooling and stirring at about 10°C. The mixture is stirred vigorously for 30 min at about 10°C and the organic phase is separated, washed with water, dried (Na 2 S0 4 ) and filtered. The filtrate is evaporated in a vacuum, whereby about 5.0 g (90 % of the theor.) of tetracyclopentyl (bromochloromethylene)bisphosphonate ( 31 P-NMR (CDCI3): δ 7.68 ppm) is obtained as a colourless oil at a concentra¬ tion of > 80 %. 2.8 g (0.005 moles) of the above obtained tetracyclopentyl (bromochloromethylene)bisphosphonate are dissolved in 6 ml of anhydrous piperidine and the mixture is stirred for 1 h on an oil bath of about 110 C C and evaporated in a vacuum. The solid residue is mixed with 10 ml of ether and the precipitate filtered and dried. The yield is about 1.8 g (60 % of the theor.) of colourless crystalline P,P'-dicyclohexyl (bromochloromethylene)bisphosponate, di- peridinium salt ( 31 P-NMR (D 2 0) : δ 8.47 ppm), at a concent¬ ration of > 90 % and wherefrom the corresponding acid may be liberated by treating with an acid. Example 16 Trimethyl (monobromomethylene)bisphosphonate and its li¬ tium salt 1.04 g (2.5 mmoles) of the tributyl methyl ammonium salt of trimethyl methylenebisphosphonate (prepared as descri¬ bed in the Example 1 from tetramethyl methylenebisphospho¬ nate and tributyl amine ( 31 P-NMR (CDCl 3 ): δ 30.51 ppm (P), 9.54 ppm (P'), 2 J PP = 6.9 Hz)) are dissolved in 40 ml of anhydrous THF and the mixture is cooled to -70°C and whi¬ le stirring 4.0 ml (5.0 mmoles) of a 2.5 M hexane solution of BuLi is added at about -70°C and stirring is continued for a further 10 minutes. To the mixture is added while stirring at about -60°C 0.80 g (5.0 mmoles) of bromine in 20 ml of anhydrous THF within 10 minutes, whereafter stir¬ ring is continued for 15 minutes at about -60 β C and the mixture is heated to room temperature. The mixture is fil¬ tered and the filtrate is evaporated in a vacuum, whereby about 0.6 g (80 % of theor.) of trimethyl (monobromomethylene)bisphosphonate, litium salt is obtai¬ ned ( 31 P-NMR (CDC1 3 ): δ 25.03 ppm (P), 11.59 (P'), J pp = 15.4 Hz), which by treatment with an acid may be converted to the corresponding acid.

Claims: Claims : 1. Novel bisphosphonic acid derivatives of the formula I in which formula R 1 , R 2 , R 3 and R 4 independently are C 1 -C 22 -alkyl, C 2 -C 22 -alkenyl, C 2 -C 22 -alkynyl, C 3 -C 10 -cycloalkyl, C 3 -C 10 -cycloalkenyl, aryl, aralkyl, silyl or hydrogen, whereby in.the formula I at least one of the groups R 1 , R 2 , R 3 and R 4 is hydrogen and at least one of the groups R 1 , R 2 , R 3 and R 4 is different from hydrogen, Q 1 is hydrogen, fluorine, chlorine, bromine or iodine, and Q 2 is chlorine, bromine or iodine, including the stere¬ oisomers, such as the geometrical isomers and optically active isomers, of the compounds, as well as the phar¬ maceutically acceptable salts of the compounds. 2. Bisphosphonic acid derivatives of the formula I according to the claim 1, wherein Q 1 and Q 2 are chlo¬ rine. 3. Compounds of the formula I according to the claim 1 or 2, wherein one of the groups R 1 -R 4 is different from hydrogen and the others are hydrogen. 4. Compounds of the formula I according to the claim 2, wherein one of the groups R 1 - R 4 is hydrogen, one of the groups R 1 - R 4 is lower alkyl and the others are hydrogen or lower alkyl, preferably methyl or ethyl. 5. Compounds of the formula I according to the claim 4, wwhheerreeiinn oonnee oorr ttwwoo ooff tthhee ggroups R-^-R 4 are lower alkyl, preferably methyl or ethyl. 6. Compounds of the formula I according to the claim 5, which is the monomethyl or monoethylester of (dichloromethylene)bisphosphonic acid. 7. Compounds of the formula I according to the claim 2, wherein one or two of the groups R 1 -R 4 is C 1 -C 18 -alkyl ur -alkenyl and- the others are hydrogen. 8. The (fluorochloro-, bro ochloro- and dibromo¬ methylene)bisphosphonic acid monomethyl- and monoethyl esters of the formula I according to the claim 1. 9. Process for the preparation of the compounds accor¬ ding to the claim 1, characterized in that a) a methylenebisphosphonic acid tetraester of the formula wherein Q 1 and Q 2 have the same meaning as in the claim 1 and the groups R 1 , R 2 , R 3 and R 4 have the same mea¬ ning as in the claim 1, except hydrogen, is subjected to selective hydrolysis to form - the corresponding triester (III), wherein one of the groups R 1 , R 2, and R 4 means hydrogen, or to a salt thereof, or - the corresponding diester (IV and/or V), wherein two of the groups R 1 , R , R 3 and R 4 mean hydrogen, or to a salt thereof, or - the corresponding monoester (VI), wherein three of the groups R 1 , R 2 , R and R 4 mean hydrogen, or to a salt thereof, or b) a bisphosphonic acid of the formula or a metal or ammonium salt thereof, or the correspon¬ ding acid tetrachloride, in which formula Q 1 and Q 2 have the same meaning as in the claim 1, is subjected to a selective esterification by reacting the same with an esterification reagent corresponding to the desired groups R 1 - R 4 , to form - the corresponding monoester (VI), wherein three of the groups R 1 , R 2 , R 3 and R 4 mean hydrogen, or - the corresponding diester (IV and/or V), wherein two of the groups R 1 , R 2 , R 3 and R 4 mean hydrogen, or - the corresponding triester (III), wherein one of the groups R 1 , R 2 , R 3 and R 4 means hydrogen, or to the corresponding ester salts of the partial esters (III to VI), or c) a phosphonate having the formula is reacted with an activated phosphate, or hydrogen phosphonate according to the formula X R 3 0 O Ml P-Z X R 4 0 in which formulas Y is hydrogen or halogen, or other leaving group, Z is hydrogen, halogen, aryloxi, sulpho- nyloxi, or alkoxi, and R 1 -R 4 and Q 1 , Q 2 have the same meaning as in the formula I, or is reacted with a phosp¬ hite corresponding to the formula X, or d) a bisphosphonite compound of the formula R 1 0 OR 3 P-C X Q Z -P XI wherein R-^-R 4 , and Q 1 , Q 2 have the same meaning as in the formula I, or the corresponding hydrogen phosphonate compound, is oxidized to the compound of the formula I, or e) a methylenebisphosphonate of the formu¬ la wherein R 1 -R 4 have the same meaning as in the claim 1, is halogenated, and, if desired, the partial ester acids obtained above in the methods a) to e) are converted to the partial ester salts, or the partial ester salts are converted to the partial ester acids, and/or, if desi¬ red, a compound obtained according to the formula I is converted to another compound according to the formula I, for example by hydrolysis, esterification, re- esterification, halogenating the methylene hydrogen, mono-dehalogenating a dihalogen substituted methylene group, or exchanging the halogen(s) tor another halogen within the scope of the definition. 10. Pharmaceutical composition, characterized in that it as the pharmaceutically active agent comprises a compound of the general formula I according to the claim 1. II. Compound of the formula I according to the claim 1 for use as a therapeutically active agent.

Inventors: NUPPONEN HEIKKI, POHJALA ESKO, VEPSAELAEINEN JOUKO, NUPPONEN, HEIKKI, POHJALA, ESKO, VEPSAELAEINEN, JOUKO
Applicants: HUHTAMAEKI OY
Application year: 1990
Main classification: C07F
IPC codes: A61K31, A61P3, C07F9