IE80555B1 - A process for the preparation of alkylphosphocholines and the production thereof in pure form - Google Patents

Abstract

Process for the preparation of C14-C18-alkylphosphocholines in a one-pot process by reaction of an n-alkanol having a chain length of C14-C18 with phosphorus oxychloride in an inert solvent or else without solvent in the presence or absence of a basic substance, and further reaction of the reaction product in an inert solvent with a choline salt in the presence of a basic substance to give the phosphoric acid diester chloride, followed by hydrolysis and isolation of alkylphosphocholine, and, if appropriate, purification by means of a mixed-bed ion exchanger or in succession with an acidic ion exchanger and a basic ion exchanger.

Description

A process for the preparation of alkylphosphocholines and the production thereof in pure form Eibl et al. (EP 225,608) describe the preparation and use of alkylphosphocholines for the treatment of tumours.

The starting substances used in the Eibl process of preparation are the n-alcohol and phosphorus oxychloride. They are reacted to phosphoric acid ester dichloride in tetrahydrofuran.

In a second step 2-aminoethanol is reacted with the phosphoric acid ester dichloride to 2-hexadecyl-l,3,2-oxaphospholan-2oxide in dioxan. Hydrolysis with 2N hydrochloric acid yields the open-chain amine which is exhaustively methylated to alkylphosphocholine with dimethyl sulphate in 2-propanol.

This process has the following disadvantages: it is necessary to isolate and purify the intermediate products. In addition, alkylating reagents are used. The use of potassium carbonate as an auxiliary base in this step of the process leads to the product having a potassium content that is undesirably high for pharmaceutical purposes.

Long-chain alkylphosphocholines having an antimicrobial effect are described by Kanetani et al., Nippon Kayaku Kaushi, 9., 1452 (1984) .

They are prepared using the following process: ethylene glycol and phosphorus trichloride are reacted to form 2-chloro-l,3,2-dioxaphospholane, the product purified by distillation is oxidized with oxygen to 2-chloro-l,3,2-dioxaphospholane-2-oxide and then distilled again. The 2-chloro-l,3,2-dioxaphospholane-2-oxide is then reacted with 1-hexadecanol to 2-hexadecyl-l,3,2-dioxaphospholane-2-oxide. The 2-hexadecyl-l,3,2-dioxaphospholane-2-oxide is reacted with trimethylamine in the autoclave to hexadecylphosphocholine, the raw product is purified both with alkaline and with acid ion exchangers and recrystallized from acetone/chloroform. The analogous process is also used to prepare the octyl-, decyl-, dodecyl, tetradecyl and octadecyl derivatives.

The disadvantage of this process is that it is necessary to work with increased pressure in the last step of the process and that the use of trimethylamine constitutes an industrial hygiene problem in the technical preparation of the substance. It is also a disadvantage that the hydrolysis-sensitive intermediate products 2-chloro-l,3,2-dioxaphospholane, 2-chloro-l,3,2-dioxaphospholane-2-oxide and 2-hexadecyl-2-oxa10 1,3,2-dioxaphospholane need to be isolated and purified. In addition, environmentally-unfriendly solvents such as benzene are used, the solvents being changed from step to step.

All known processes use chromatographic methods for working up and purifying the raw products.

However, chromatographic working up processes of this kind have the following disadvantages: - their conversion to a technical scale causes difficulties since the dimensions of the stationary phase cannot be increased at will, - chromatographic processes are time-consuming.

The invention relates to a new, advantageous method of preparing and working up alkylphosphocholines.

It has surprisingly been found that the process of the invention achieves a higher total yield, despite the use of one less purification step than in previously known processes. In addition, the invention uses less solvent.

The process of the invention also avoids the use of alkylating reagents such as dimethyl sulphate which lead to a high potassium content of the product due to the use of potassium carbonate as an auxiliary base. The potassium content must be kept as low as possible in substances used as pharmaceutically active substances.

The process of the invention avoids the time-consuming chromatographic step during working up.

The product purity achieved in the process claimed is greater than in the known processes.

The first step in the conversion consists of the reaction of phosphorus oxychloride, optionally in the presence of halogenated hydrocarbons, saturated cyclic ethers, acyclic ethers, saturated hydrocarbons with 5 to 10 carbon atoms, liquid aromatic hydrocarbons which can also be substituted by halogen (in particular chlorine) or mixtures of the above mentioned solvents, and optionally in the presence of a basic substance conventionally used for this purpose, with an n-alkanol having a chain length of 14-18 hydrogen atoms.

Halogenated hydrocarbons that may for example be used are hydrocarbons of 1 to 6 carbon atoms, where one or several or all of the hydrogen atoms are replaced by chlorine atoms. It is for example possible to use methylene chloride, chloroform, ethylene chloride, chlorobenzene, dichlorobenzene. When halogen-substituted aromatic hydrocarbons are used, these are preferably substituted with 1 or 2 halogen atoms.

Saturated cyclic ethers that may be used are for example ethers with a ring size of 5-6 which consist of carbon atoms and 1 or 2 oxygen atoms.

Examples thereof are tetrahydrofuran and dioxan.

The acyclic ethers consist of 2 to 8 carbon atoms and are liquid. Examples that may be considered: diethylether, diisobutylether, methyl-tert.-butylether, diisopropyl ether.

Saturated hydrocarbons that may be considered are unbranched and branched hydrocarbons that consist of 5 to 10 carbon atoms and are liquid. Examples that may be considered are pentane, hexane, heptane, cyclohexane.

Aromatic hydrocarbons that may for example be considered are benzene and alkyl-substituted benzenes where the alkyl substituents consist of 1 to 5 carbon atoms.

Basic substances that may be considered both for the reaction of the phosphorus oxychloride with the n-alkanol and also for the subsequent reaction with the choline salt are amines, for example aliphatic amines of the formula NR1R2R3, where Rlr R2 and R3 are the same or different and represent hydrogen or Cj.-Cg-alkyl, aromatic amines such as pyridine, picoline, quinoline.

During the reaction with the choline salt it is possible to add the basic substance required herefor at the same time as the choline salt or before the choline salt. For the reaction with the choline salt a solvent is needed in any case; in other words, if the first reaction step is conducted without a particular solvent, one has to be added at this stage. The mol ratio of phosphorus oxychloride to the alkanol is for example between 1,5:1 to 1:1.1.

The choline salt is for example used in excess in relation to the alkanol (about 1.1 - 1.5 molar excess).

If the reaction of the phosphorus oxychloride with the alkanol occurs in the presence of a basic substance, the amount of the basic substance is for example 1 to 3 Mol related to 1 Mol POC13.

For the subsequent reaction with the choline salt the amount of basic substance used is for example 1 to 5 Mol related to 1 Mol alkanol.

The reaction temperature of the reaction of phosphorus oxychloride with n-alkanol lies between -30°C and +30°C, preferably -15°C and +5°C, in particular -10°C and -5°C.

The reaction time of this conversion is for example 0.5-5 hours, preferably 1-3 hours, in particular 1.5-2 hours. If the reaction occurs in the presence of a basic substance, it is generally quick (about 30 minutes).

The choline salt is then added in portions or in its entirety. Salts of choline that may for example be used are salts with mineral acids (such as sulphuric acid, hydrochloric acid), and also salts of choline with organic acids such as acetic acid, para-toluenesulphonic acid and the like.

This reaction step occurs in an inert solvent. Solvents that may be considered here are the same that are used to react the phosphorus oxychloride with the n-alkanol if this reaction occurs in a solvent.

The basic substance is then dissolved in one of the stated solvents or added dropwise without solvent.

The following are preferably used as solvent for the basic substance: halogenated hydrocarbons, saturated cyclic ethers, acyclic ethers, saturated hydrocarbons with 5 to 10 carbon atoms, liquid aromatic hydrocarbons or mixtures of the above mentioned solvents.

These are the same solvents that may be used for the reaction of phosphorus oxychloride with the n-alkanol.

Addition of the basic substance causes the temperature to rise. Care must be taken that the temperature is maintained within a range between 0°C to 40°C, preferably 10°C to 30°C, in particular at 15°C to 20°C.

The reaction mixture is then still stirred at 5°C to 30°C, preferably 15°C and 25°C (for example 1 hour to 40 hours, preferably 3 hours to 15 hours).

The hydrolysis of the reaction mixture occurs through addition of water, it being necessary to maintain a temperature between °C and 30°C, preferably 15°C and 30°C, in particular between °C and 20°C.

The previously mentioned hydrolysis liquids can also contain basic substances. Basic substances that may be considered include carbonates and hydrogen carbonates of the alkaline and alkaline earth metals.

To complete the hydrolysis the mixture is then stirred for a further 0.5 hours to 4 hours, preferably 1 to 3 hours, in particular 1.5 to 2.5 hours at 10°C to 30°C, preferably at 15°C to 25°C, in particular at 18°C to 22°C.

The reaction solution is then washed with a mixture of water and alcohols (preferably aliphatically saturated alcohols with 1 to 4 carbon atoms) which may optionally also contain a basic substance.

The mixing ratio water:alcohol may for example lie between 5 and 0.5, preferably 1-3 (V/V).

Basic substances that may be considered as washing liquid are for example carbonates and hydrogen carbonates of the alkaline and alkaline earth metals as well as ammonia in the form of the aqueous solution. A 3% sodium carbonate solution in water is particularly preferred.

It is then optionally possible to wash the reaction solution with an acid solution.

Acid washing is advantageous to remove not yet reacted basic portions of the reaction solution, in particular when methylene chloride is used as solvent.

The washing solution consists of a mixture of water and alcohols. Mixtures of aliphatically saturated alcohols with 1 to 4 carbon atoms are preferably used, an acid substance also optionally being present. The mixing ratio water:alcohol may for example lie between 5 and 0.5, preferably 1-3 (V/V).

Acid substances that may be considered for the washing liquid are for example mineral acids and organic acids, for example hydrochloric acid, sulphuric acid or tartaric acid, and citric acid.

A 10% solution of hydrochloric acid in water is particularly preferred.

The mixture is then washed one again with a mixture of water and alcohols. Mixtures of aliphatic saturated alcohols with 1 to 4 carbon atoms are preferably used, it also being possible for a basic substance to be optionally present.

The mixing ratio water: alcohol may for example lie between 5 and 0.5, preferably 1-3.

The washed phases are then combined and dried in conventional manner and the solvent is then removed (preferably under reduced pressure, for example 5-100 mbar) optionally after addition of 1.5-3 litres, preferably 2-2.5 litres of an aliphatic alcohol (related to 1 part by weight of dried product). Alcohols that may for example be used are saturated aliphatic alcohols with a chain length of 1 and 5 carbon atoms. The particularly preferred alcohol here is n-butanol, isopropanol. The purpose of this alcohol treatment is to remove the residual water completely.

The product so-obtained can be purified in the conventional manner (e.g. by chromatography, recrystallization).

An alkylphosphocholine raw product or the solid residue as described above is for example suspended in saturated aliphatic ketones (3-6 carbon atoms), for example acetone, butanone, methyl-tert.-butylketone, stirred for 1 to 4 hours, preferably 2 hours, suction filtered and dried at 20°C to 50°C in a vacuum at 5 Torr to 100 Torr.

The following purification process is, however, particularly preferred: The product prepurified in this manner is taken up in anhydrous alcohols (C-l to C4) or in alcohols which contain not more than up to 5 percent by weight of water at 20°C to 60°C, preferably 40°C and insoluble constituents filtered off.

Alcohols that may for example be used are methanol, ethanol, 5 isopropanol, butanol, isobutanol.

The prepurified product may also be dissolved in water.

The filtrate obtained is then stirred with a mixed-bed ion exchanger, for example AmberliteR MB3, for example for 1 to 5 hours, preferably 2 hours at 10°C to 50°C, preferably 20°C.

Instead of a mixed-bed ion exchanger the purification may also be effected simultaneously or successively with an acid ion exchanger and a basic ion exchanger.

Ion exchangers which may also be used are all insoluble solids which contain ion exchanging groups.

Acid ion exchangers are those which contain for example acid groups such as sulphonic acid groups, carboxyl groups. Examples are ion exchangers with sulphonic acid groups in a polystyrene matrix such as AmberliteR IR 120, DowexR HCR, DuoliteR C 20 or LewatitR S 100.

Weakly acid ion exchangers are for example those which carry carboxylic acid groups on the basis of a polyacrylic acid matrix, such as AmberliteR IRC 76, DuoliteR C 433 or ReliteR CC.

Basic ion exchangers that may for example be considered are those carrying on a polymer matrix (e.g. polystyrene matrix) primary, secondary, tertiary or quaternary amino groups such as DuoliteR A 101, DuoliteR A 102, DuoliteR15 A 348, DuoliteR A 365, DuoliteR A 375, AmberliteR IRA 67, DuoliteR A 375, AmberliteR IRA 458 and DuoliteR A 132.

Mixed-bed ion exchangers are mixtures of acid and alkaline ion exchanger resins, such as AmberliteR MB1, AmberliteR MB2, AmberliteR MB3 and AmberliteR MB6.

It is also possible to use all conventional ion exchangers in the process.

Reference is also made to Ullmann’s Encyclopedia of Industrial Chemistry, 5th Edition (1989), Volume A14, p. 450.

Following vacuum suctioning of the ion exchanger resin the mixture is evaporated under reduced pressure (for example 20 Torr to 200 Torr) at 40°C to 70°C and the mixture is then recrystallized from halogenated hydrocarbons or from alcohol/ketone mixtures.

Halogenated hydrocarbons that may for example be considered for the recrystallization are hydrocarbons containing 1 to 6 carbon atoms where one or several or all carbon atoms are replaced by chlorine atoms.

It is for example possible to use methylene chloride, chloroform, ethylene chloride, chlorobenzene.

Alcohols that may be considered are saturated aliphatic alcohols with 1 to 6 carbon atoms and 1 to 2 hydroxyl groups. Ketones that may be considered are saturated, aliphatic ketones with 3 to 8 carbon atoms.

The mixing ratio alcohol:ketone is 1 to 1-5 (volume/volume). An ethanol/acetone mixture in the ratio of 1:1 (V/V) is particularly preferred.

The crystals of alkylphosphocholine obtained are suction filtered and if necessary washed for example with saturated hydrocarbons containing 1 to 6 carbon atoms. (Temperature of the washing liquid for example 15 to 30°C).

Drying is effected for example in a vacuum at 40°C to 80°C over conventional drying agents, for example phosphorus pentoxide or silica gel.

Example 1 Preparation of hexadecyl phosphocholine 1.0 Mol (92 ml) POC13 in 1.5 1 chloroform are added to a 6-litre stirring apparatus under nitrogen and cooled in an ice bath to 5°C. 0.90 Mol (218 g) hexadecanol are dissolved in 700 ml chloroform and added dropwise together with 4.00 Mol (320 ml) pyridine at a temperature of 5 - 12°C. Dropping time: 1.25 hours. The dropping funnel is then flushed with the remaining 300 ml chloroform. After one and a half hours post-stirring at 0 - 5°C, 1.35 Mol (372 g) solid choline tosylate are added and then 400 ml pyridine added dropwise over 15 minutes. This causes the temperature to rise to 20°C. The ice bath is removed and the reaction mixture is stirred at room temperature for 3 hours. For purposes of hydrolysis 150 ml water are added dropwise over 20 minutes, the temperature rising from 25°C to 36°C. After stirring for half an hour, the reaction solution is washed in each case once with 1.50 litres water/methanol (1:1) , 1.50 litres 3% sodium carbonate/methanol (1:1) and 1.50 litres water/methanol (1:9). The chloroform phase washed in this manner is dried over sodium sulphate and evaporated in a rotary evaporator in a vacuum after addition of 50 ml i-propanol. n-butanol is added for drying and the mixture is evaporated in a rotary evaporator again.

Purification is carried out as follows: The residue is suspended in 2.0 litres acetone, stirred for approx. 2 hours, suction filtered and dried at 30°C in a vacuum. Raw yield: 325 g (87 %) . The raw product is taken up in 3.0 litres absolute ethanol and insoluble portions filtered off. The filtrate is stirred for two hours with 1.0 litres mixed-bed ion exchanger Amberlite MB 3R(FLUKA). After suction filtration of the ion exchanger resin the mixture is evaporated in a rotary evaporator in a vacuum and then recrystallized once from 0.70 litres methylene chloride. Complete crystallization is achieved in the refrigerator. The crystals are suction filtered and washed with pentane. The mixture is then dried in a vacuum at 30°C over phosphorus pentoxide.

Yield 193 g (0.47 Mol, 53 %) The reaction product has a melting point of 241 - 245°C.

Examples 2-5 are prepared according to the same procedure.

Example 2: II ® D-19 3 9 0 : H3C- (CH2) 13-0-P-0- (CH2) 2-N (CH3) 3 i® Mp: 260°C (disintegration) C19H42NO4P (379.52) TL: 89 a (chloroform/methanol/ammonia 25% =70:20:10) Rf :0.27 EA: calc. C 60.13% H 11.16% N 3.69% *h2o 57.41% 11.16% 3.52% found C 57.40% H 11.42 N 3.61% 57.43% 11.47% 3.65% •H-NMR: (250 MHz, CDC13) <5 = 0. 90 ppm (t,3H) 3.80 1.25 (m,22H) 3.85 (m,2H) 1.55 (p,2H) 4.25 (m,2H) 3.40 (s,9H) Example 3: D-20403 : H3C-(CH2)14-O-P-O-(CH2)2-N(CH3)3 £ Mp: 244°C (disintegration) C20H44NO4P (393.55) TL: 89 a (chloroform/methanol/ammonia 25% =70:40:10) Rf :0.49 EA: calc. *2H2O found C 61.04% H 11.27% 11.26% H 10.99 10.85% N 3.56% 3.26% N 3.67 3.59% C 55.92% 56.14% 55.74% 'H-NMR: (250 MHz, cdci3) δ = 0.90 ppm (t,3H) 3.80 (q,2H) 1.30 (m,24H) 3.85 (m,2H) 1.55 (p,2H) 4.25 (m,2H) 3.40 (s,9H) Example 4: O II Φ D-19767: H3C-(CH2) 16-O-P-O-(CH2) 2-N(CH3) 3 is Mp: 254 - 256°C C22H48NO4P (421.61) TL: 127 c (I-butanol/glacial acetic acid/water=60:20:20) Rf:0.34 EA: calc. *H2° found C 62.68% 60.11% C 60.2% H 11.48% 11.46% H 11.7 N 3.32% 3.19% N 3.1% 60.5% Ή-NMR: (250 MHz, CDC13) δ = 0.90 ppm (t,3H) 3.8 1.25 (m,28H) 3.85 (m,2H) 1.60 (p,2H) 4.25 (m,2H) 3.40 (S,9H) 11.7% Jr (q,2H) Example 5: O II D-19391: H3C-(CH2) 17-O-P-O- (CH2) 2-N(CH3) 3 0» Mp: 258°C (disintegration) C23H50NO4P (435.62) TL: 126 (I-butanol/glacial acetic acid/water=40:10:10) Rf:0.13 EA: calc. *h2o found C 63.41% H 11.57% 11.55% H 11.93 12.02% N 3.22% 3.09% N 3.15% 3.15% C 60.90% 60.80% 60.83% 'H-NMR: (250 MHz, CDC13) δ = 0.90 ppm (t,3H) 3.80 (q,2H) 1.25 (m,30H) 3.85 (m,2H) 1.60 (p,2H) 3.40 (s,9H) 4.30 (m,2H)

Claims (5)

1. Patent Claims

1. Process for the production of C 14 -C ia alkylphosphocholines by reacting an n-alkanol with phosphorus oxychloride and a choline salt, characterised in that, in a single-vessel process, an n-alkanol having a chain length of C 14 -C 18 is reacted with phosphorus oxychloride in an inert solvent or also without a solvent in the presence or absence of a basic substance, the resultant product is further reacted, without isolation and purification, with a choline salt in an inert solvent in the presence of a basic substance to yield the phosphoric acid diester chloride and the alkylphosphocholine is liberated and isolated by subsequent hydrolysis.

2. Process for the production of C 14 -C ia alkylphosphocholines according to claim I, characterised in that a solution of the alkylphosphocholines obtained using the process according to claim 1 is treated in ah organic medium with a mixed bed ion exchanger or in succession with an acidic ion exchanger and a basic ion exchanger.

3. . Process for the production of C 14 -C 18 alkylphosphocholines according to claim 1, characterised in that the temperature during the reaction of the crude product with the choline salt/base is between 0°C and 40°C.

4. A process according to Claim 1 for the preparation of a C., .-C., o -alkylphosphocholine, substantially as I 4 1 O hereinbefore described and exemplified.

5. A C,C. o -alkylphosphocholine, whenever prepared by a 14 Io process claimed in a preceding claim.