MXPA99009219A - Process for synthesizing phosphodiesters - Google Patents

Abstract

An improved process for the production of phosphodiester compounds having formula (1). These compounds are particularly useful as contrast agents for diagnostic imaging. The process avoids the need for multiple isolation and purification steps otherwise reduced due to the formation of multiple intermediates.

Description

PROCESS TO SYNTHESIZE PHOSPHODIESTERS FIELD OF THE INVENTION The present invention relates to an improved process for the production of phosphodiester compounds. In particular, the invention relates to an improved process for preparing phosphodiester compounds which are useful as contrast agents for diagnostic imaging, and more particularly, for preparing diethylenetriamine-pentaacetic acid compounds ("DTPA" ) that comprise fos fodies teres.

BACKGROUND OF THE INVENTION Many important biological substances, including phospholipids, oligonucleotides, deoxynucleosides, nucleotides and nucleosides, exist as symmetric and asymmetric phosphodies. The utility of these phosphodiester compounds in medical applications is well known. See, for example, Desseaux et al., "Synthesis of Phosphodiester and Triester Derivatives of AZT with Tethered N-Methyl Piperazine and N, N, 't rimethyl ethyl enedi amine," Bioorg & Med. Chem. Letters, vol. 3) No. 8, pp. 1547-50 (1993); PCT publication no. WO 96/27379. Recently, the PCT publication no. WO 96/23526, incorporated herein by reference, discloses phosphodiester compounds which are useful as contrast agents for diagnostic imaging. Various methods are known for producing the phosphodiester compounds, based on chemical compounds P (III). In general, phosphorylation plays an important role in the synthesis of the phosphodiester compounds. Although all known synthetic methods for producing phosphodiester are affected by several of the problems including how to carry out phosphorylation. A method to produce phosphodies teres involves the use of chemical compounds of phosphoramidite. See, for example, Bannwarth et al., "A Simple and Effective Chemical Phosphorylate ion Procedure for Biomolecules," Helvética Chimica Acta, vol. 70, pp. 175-186 (1987); Bannwarth et al., "Bis (allyloxy) (diisopropylamino) phosphine as a New Phosphinylation Reagant of the Phosphorylation of Hydroxy Functions, "Tetrahedron Letters, vol 30 no. 32, pp. 4219-22 (1989); Moore et al., "Conceptual Basis of the Selective Activation of Bis (dial kylamino) methoxyphosphines by Weak Acids and Its Application to the Preparation of Deoxynucleos ide Phosphoramidites in Situ," J. Org. Chem., Vol. 50, pp. 2019-2025 (1985), _ Hebert et al., "A New Reagant for the Removal of the 4 -Methoxybenzyl Ether: Application to the Synthesis of Unusual Macrocyclic and Bolaform Phosphatidycholines," J. Org. Chem., Vol. 57, pp. 1777-83 (1992); Desseaux et al., "Synthesis of Phosphodiester and Triester Derivatives of AZT with Tethered N-Methyl Piperazine and N, N, N 't rimethylethylenediamine," Bioorg. & Med. Chem. Letters, vol. 3) No. 8, pp. 1547-50 (1993); Pirrung et al., "Inverse Phosphotries ter DNA Synthesis Using Photochemically-Removable Dimethoxybenzoin Phosphate Protecting Groups, "J. Org. Chem., Vol 61, pp. 2129-36 (1996). However, these methods for preparing phosphoramidite are affected by the fact that phosphoramidites are typically unstable compounds. (both chemically and kinetically) and in the purification by distillation can ignite or cause an explosion.Moreover, the methods for preparing phosphoramidite in general are not suitable for producing the phosphodiester compounds on a commercial basis. Phosphoramidite starting materials are very expensive and are not readily available, and because methods that use phosphoramidites tend to involve additional process steps (for example, the additional step of breaking down the protective groups after phosphorylation) as well as the steps of multiple isolation and / or purification of intermediates, methods involving the use of phosphodichloridates As the f_o_sforilación agent are affected by similar problems. See, for example, Martin et al., "General Method for the Synthesis of Phospholipid Derivatives of 1,2-0-Diacyl-sn-glycerols," J. Org. Chem., Vol. 59, pp. 4805-20 (1994); Martin et al., "A General Protocol for the Preparation of Phospholipids via Phosphate Coupling," Tetrahedron Letters, vol. 29, _ no. 30, pp. 3631-34 (1988); Lammers et al., "Synthesis of Phospholipids via Phosphot ries ter Intermediates," J. Roya Netherlands Chem. Soc'y, 98/4, __ pp. 243-250 (April 1979); Martin et al., "Synthesis and Kinetic Evaluation of Inhibitors of the Phosphat idylinositol-Specific Phospholipase C from Ba ci l l us cereus," J. Org. Chem., Vol. 61, pp. 8016-23 (1996). Another method used for the production of phosphodiester compounds involves the use of PC13 to generate acid phosphonate intermediates. See, for example, Lindh et al., "A General Method for the Synthesis of Glycerophospholipids and Their Analogues via H-Phosphonate Intermediates," J. Org. Chem. , vol. 54, pp. 1338-42 (1989), Garcia et al., "Synthesis of New Ether Glycerophospholipids Structurally Related to Modulator," Tetrahedron, vol. 47, no. 48, pp. 10023-34 (1991); Garigapati et al., "Synthesis of Short Chain Phosphatidylinositols," Tetrahedron Letters, vol. 34, no. 5 pp. 769-72 (1993). However, this method requires the use of a coupling reagent that can either be purchased or synthesized independently and thus cause the methods to be expensive or more complex. In addition, multiple steps of isolation and purification of the intermediates are required, often with laborious drying conditions for the H-phosphonate intermediate. Accordingly, there is a need for a safe, efficient and economical process for the production, in high yields, of phosphodiester compounds with the potential to have a wide variety of substituents that does not require the use of either a protecting group or an agent coupling In particular, there is a need for a process that could be carried out in a reaction vessel and does not require multiple stages of isolation and purification due to the formation of multiple intermediates.

BRIEF DESCRIPTION OF THE INVENTION The present invention relates to a safe, more efficient and less expensive process for preparing the phosphodiester compounds, and more particularly, phosphodies teres having the formula: According to the present invention, the process comprises the steps of: (a) coupling PC13 with an alcohol to obtain a substituted dichlorophosphine; (b) coupling the fine dichlorophos with an amine base to obtain a fine bis (amino) fos; (c) coupling __ the fine bis (amino) fos with a second alcohol, which "may be the same or different from the alcohol used in step (a) to obtain a disubstituted (amino) fos, (d) and react the (amino) phosphine with water and an oxidizing agent to obtain the desired phosphodiester compound The process according to this invention avoids the use of unstable phosphorylating agents as well as the need to use a protecting group or a coupling agent. In this way, the present method avoids unnecessary process steps such as the synthesis of deprotection and coupling reagents In a preferred embodiment of this invention, the synthetic process for the production of phosphodiester is carried out in a container of reaction, avoiding the need for multiple stages of isolation and / or purification.

DETAILED DESCRIPTION OF THE INVENTION For the invention described herein to be understood more broadly, the following detailed description is set forth. The present invention provides an improved process for preparing phosphodiester compounds of the general formula: wherein R and R may be the same or different and are selected from the group consisting of groups of organic, straight, branched, or cyclic aliphatic, aryl, heterocyclic, peptidic, peptoid, deoxyribo- or ri-nucleotide or nucleoside chelating agents. , or cyclic or acyclic, which as a whole may optionally be substituted with one or more substituents of nitrogen, oxygen, sulfur, halogen, aliphatic, amide, ester, sulfonamide, aryl, acyl, sulfonate, phosphate, hydroxyl, or organometallic. In a preferred aspect of the invention, all synthetic steps are performed in a reaction vessel, excluding the need for multiple stages of isolation and / or purification. The present invention demonstrates an efficient and high-throughput process for producing phosphodiester compounds that do not depend on expensive or unstable starting materials and do not require the use of either protective agents or coupling agents. In addition, the process is efficient in the generation of phosphodiester bonds among a wide variety of substituents.

PROCESS SCHEME In accordance with this invention, an alcohol ROH, where R has the same meaning as stated above, is reacted with PCI3, preferably at a molar ratio of 1: 1, to form a reaction product of dichlorophosphine (I): PCU. solvent (I) ROH ROPCh This reaction is carried out in the presence of an ethereal or hydrocarbon solvent and is carried out at a temperature of from about -50 ° C to about 15 ° C, preferably from about -10 ° C to about -5 ° C, for a period of from about 30 minutes to about 3 hours, preferably from about 1 to about 1.5 hours. The solvent can be any ethereal or hydrocarbon solvent and preferably, 1Q can be selected of the group consisting of heptanes, methyl-t-butyl ethers, dioxanes, tetrahydrofurans, diethyl ethers, and ethylene glycol alkyl ethers. More preferably, the solvent is tetrahydrofuran. The dichlorophosphine (I) is then reacted with about 5 to about 6 equivalents of an amine base to form a reaction product (II) of bis (amino) phosphine: (p) This reaction is also carried out in the presence of an ethereal solvent or hydrocarbon, as described above, and is carried out at a temperature of about -50 ° C to about 15 ° C, preferably about -10 ° C about -5 ° C, for a period of about 30 minutes to about 3 hours, preferably from about 15 to about 30 minutes. The base used to form the reaction product (II) can be any amine base, preferably a base having a pKa value of about 5 to about 11 and more preferably is selected from the group consisting of imidazole, 2, 4 -dimet il imidazol, lH-tetrazal, dialqui lamines (methyl, ethyl, butyl), pyridine, piperazine, piperidine, pyrrole, 1H-1, 2, 3-triazole, and 1, 2,4-t-riazole. In a more preferred embodiment, the base is imidazole. The compound (II) bis (amino) phosphino is then reacted with about 0.75 to about 1.0 equivalents of a second alcohol R1OH, wherein R1 has the same meaning as stated above, to form a reaction product (III) of (amino) phosphino: This reaction is carried out in the presence of an ethereal or hydrocarbon solvent and is carried out at a temperature of from about -50 ° C to about 15 ° C, preferably from about -10 ° C to about -5 ° C, for a period of from about 30 minutes to about 3 hours, preferably from about 1.0 to about 1.5 hours. The solvent can be any ethereal or hydrocarbon solvent and can preferably be selected from the group consisting of heptanes, methyl t-butyl ethers, dioxanes, tetrahydrofurans, 1,3-dioxalanes, diglymes, diethyl ethers, dialkyl ethers and ethylene glycol diakyl ethers . More preferably, the solvent is tetrahydrofuran. Finally, the fine (amino) fos compound (III) is reacted with about one equivalent of acidic water, preferably having a pH of about 2.5 to about 5, and about 1 or more equivalents of an oxidizing agent to form the desired phosphodiester compound (IV): The oxidizing agent can be any peroxide-type oxidant and is preferably selected from the group consisting of periodates. Most preferably, the oxidizing agent is sodium periodate.

The above hydrolysis and oxidation are carried out in a solvent mixture at a temperature from about -15 ° C to about 25 ° C, preferably from about 0 ° C to about 2 ° C, for a period of about 10 a about 24 hours, preferably from about 10 to about 15 hours. The solvent mixture comprises any combination of solvents selected from the group consisting of ethereal or hydrocarbon solvents. Preferably, the solvent mixture comprises tetrahydrofuran, heptane and toluene at a volume ratio of 10: 10: 1.

USE OF PROCESS PRODUCTS It has been found that the above process is particularly useful in the preparation of contrast agents for diagnostic imaging. Examples of phosphodiester contrast agents that can be prepared by this improved process include the compounds shown below, as well as others described in PCT publication no. WO 96/23526.

MS-31S KS-317 MS-322 MS-323 MS-32S XS-32C HS-327 Kl-321 In these cases, it is contemplated that at least one of the two alcohols (ROH, R1OH) as defined herein further comprises a cyclic or acyclic organic chelating ligand, with any sensitive functional groups (e.g. carboxylates) on a chelate protected with appropriate groups (e.g., t-butyl groups). Suitable chelating ligands are well known in the art. For example, wherein the phosphodiester compound will be used as a contrast agent for magnetic resonance imaging, preferred chelating agents include: Magnevist. Doppler Dimearem Dipearem gadoterate meglumine DTPA DOTA The removal of any protecting groups on the chelate as well as the complexing of the chelate with the desired metal can be carried out after carrying out the synthetic process to produce the phosphodiester of this invention by methods well known in the art. See, for example, Grote et al., "Stereocont rolled Synthesis of DTPA Analogues Branged in the Ethylene Unit," J. Org. Chem., 60: 6987-97 (1995); Kang et al., "Synthesis, Characterization, and Crystal Structure of the Gadolinium (III) Chelate of (lR, 4R, 7R) -c., A *, a" -Trimethyl-l, 4,7,10-tetraazacyclododecane- 1, 4, 7 -t riacet ic Acid (D03MA), "Inorg. Chem., 3_2_: 2912-18 (1993) and the references cited therein It is also contemplated that for the phosphodiester contrast agents, alcohol (ROH or RxOH) can comprise an entity designated to facilitate the location of the resulting agent to the tissue, cell, protein, receptor or desired area for the image to be formed Examples of these entities include lipophilic or amphiphilic substances, receptor ligands, antibodies , or antibody fragments, peptides, or other biomolecules that are known to be concentrated in the specific biological component desired for the image to be formed.For this invention to be better understood, the following example is established. for purposes of illustration and do not pretend to limit the scope of this invention in any way.

EXAMPLE The preparation of [(4,4-diphenylcyclohexyl) phosphooxymethyl] diethylenetriamin-penta-acetic acid is shown in Scheme I below: Scheme I H20 N »104 In a single reaction vessel containing a solution of phosphorous trichloride (13.2 mL, 0.151 mol) in tetrahydrofuran (202 mL) was added a solution of 4, -di-phenyl-cyclohexanol (1_) (38.34 g, 0.152 mol) in tetrahydrofuran (243 ml) while stirring and maintained at an internal temperature of -6.2 ° C to -5.3 ° C for 1.5 hours. The mixture was then stirred for an additional 34 minutes providing a reaction product of fine dichlorophos (2), which has a 31P NMR chemical change of 174.28 ppm. To this solution, imidazole (51.34 g, 0. 753 mol) in tetrahydrofuran (243 ml) while stirring and maintaining an internal temperature of -7.8 ° C to -3.6 ° C for 37 minutes. The resulting mixture was then stirred for an additional 20 minutes providing a solution of a bis (amino) phosphino (3_) reaction product having a 31P NMR chemical change of 106.36 ppm. To this mixture was added a solution consisting of penta- -butyl ines ter (4_) of 2- (R) -hydroxymethyldiethylene riamin penta-acetic acid, (160.0 g, 0.128 mol, purity: 56.32% by weight) in heptane (114 ml) while stirring and an internal temperature of -6.8 ° C to -4.8 ° C was maintained for 1 hour and 6 minutes. This mixture was then stirred for an additional 23 minutes providing a solution (5_) which had a 31P NMR chemical change of 123.8 ppm. Finally, water (202 ml) was added over a period of about 1 minute while maintaining an internal temperature of -6.5 ° C to 6.5 ° C. The mixture was stirred for 5 minutes followed by the addition of heptane (620 ml), toluene (70 ml) and 5N aqueous hydrochloric acid (202 ml) for 5 minutes while maintaining an internal temperature of 1.0 ° C to 12.1 ° C. . Sodium periodate (22.6 g, 0.106 mol) was then added over a period of 3 minutes while maintaining an internal temperature of 10.5 ° C. The reaction mixture was warmed to room temperature over 35 minutes and stirred for an additional 2.5 hours providing a solution (6_) with a 31P NMR chemical change of 4.27 ppm. The layers were separated and the organic layer was washed with 10% aqueous sodium thiosulfate (2 x 809 mL). To the above organic layer was added tetraoctylammonium bromide (8.21 g, 0.015 mol). Concentrated hydrochloric acid (11.51 M, 405 mL) was then added over a period of 22 minutes while maintaining an internal temperature of 22.8 ° C to 25.0 ° C. This mixture was stirred for 16.0 hours to give a compound (7_) with a chemical change of 31 P NMR of 7.78 ppm. The layers were separated and the organic layer was discarded. Aqueous 8M aqueous sodium hydroxide (630 mL) was added to the above aqueous layer until a pH of 6.56 was recorded. The solution was concentrated under reduced pressure (50 ° C to 55 ° C, vacuum 85 mm Hg) until 400 mL of the solvent was collected (approximately 1 hour). The solution was cooled to room temperature and amberlite resin XAD-4 (92.0 g) was added. The suspension was stirred for 50 minutes at room temperature and filtered to give a light yellow aqueous solution (1.1 L). The previous solution was loaded on reverse phase silica gel C-18 (271 g, wet-packed in methanol and then washed with 800 mL of methanol, 800 mL of methanol / water, 1: 1 and 800 mL of water) and eluted with water. The first 1.0 L of the collected eluent was discarded and the next 1.3 L rec ected were conserved. To the preserved solution was added 6N aqueous hydrochloric acid (60 mL at a pH = 2.15) and 3N aqueous hydrochloric acid (30 mL at a pH = 1.63). The suspension was stirred for 1.25 hours and filtered. The solid was washed with aqueous solution at a pH of 1.67 (500 mL) and dried (48-50 ° C, 4-6 mm Hg) at a constant weight (18.0 hours) to obtain an off-white solid, the compound of the formula : (65.5 g, Yield: 68.89% Purity: 99.45% by weight, 98.95% by area, 3.02% of water and 97.81% of chelated products).

Claims (16)

1. CLAIMS 1. A process for preparing phosphodiester compounds having the formula: characterized in that R and R 'may be the same or different and are selected from the group consisting of groups of organic, straight, branched, or cyclic aliphatic, aryl, heterocyclic, peptidic, peptoido, deoxyribo- or ribo-nucleotide chelating agents or nucleosidic, or cyclic or acyclic, all optionally substituted with one or more substituents of nitrogen, oxygen, sulfur, halogen, aliphatic, amide, ester, sulfonamide, acyl, sulfonate, phosphate, hydroxyl, or organometallic, the process is carried out in a reaction vessel and comprises the steps of: (a) reacting an alcohol ROH with PC13 in the presence of a solvent to form a fine dichlorophos compound having the formula: (b) coupling the dichlorophosphine compound formed in step (a) with an amine base in the presence of a solvent to form a bis (amino) phosphino compound having the formula: (c) coupling the bis (amino) phosphino compound formed in step (b) with a second alcohol R -'- OH, in the presence of a solvent, wherein the second alcohol may be the same or different from that of the step ( a), to form a fine (amino) fos compound having the following formula: (d) and subjecting the fine (amino) fos compound formed in step (c) for hydrolysis and oxidation.
2. 2. The process according to claim 1, characterized in that the alkoxydichlorophosphine compound formed in step (a) is reacted with about 5 to about 6 equivalents of amine base.
3. 3. The process according to any of claims 1 or 2, characterized in that the amine base has a pKa value of about 5.0 to about 11.0.
4. 4. The process according to claim 3, characterized in that the base is selected from the group consisting of imidazole, 2,4-dimethylimidazole, lH-tetrazole, dialkylamines (methyl, ethyl, butyl), pyridine, piperazine, piperidine, pyrrole, , 1,2, 3-triazole and 1, 2, 4 -1ria zol.
5. 5. The process according to claim 4, characterized in that the base is imidazole.
6. 6. The process according to claim 1, characterized in that approximately one equivalent of ROH is reacted with approximately one equivalent of PC13
7. 7. The process according to claim 1, characterized in that the solvent used in steps (a), (b) ) and (c) may be the same or different and is selected from the group consisting of ethereal and hydrocarbon solvents.
8. 8. The process according to claim 7, characterized in that the solvent is selected from the group consisting of heptanes, methyl t-butyl ethers, dioxanes, tet rahydrofurans, 1,3-dioxalan, diglymes, diethyl ethers, dialkyl ethers, and ethylene glycol diakyl ethers.
9. 9. The process according to claim 8, characterized in that the solvent is tetrahydrofuran.
10. 10. The process according to claim 1, characterized in that the alkoxy (amino) phosphino compound formed in step (b) is coupled with about 1 equivalent of R1OH.
11. 11. The process according to claim 1, characterized in that the hydrolysis and oxidation of the dialkoxy (amino) fos compound formed in step (c) is carried out with water and an oxidizing agent in a solvent at a temperature varying from about -15 ° C to about 25 ° C for a period of 10 to 24 hours.
12. 12. The process according to claim 11, characterized in that the oxidizing agent comprises sodium periodate.
13. 13. The process according to claim 11, characterized in that the solvent comprises a mixture of tetrahydrofuran, heptane and toluene.
14. 14. A process for preparing phosphodiester compounds comprising the steps of: (a) reacting a 4,4-diphenylcyclohexanol compound with PC13 to obtain 4,4-diphenycyclohexyloxy-dichlorophoses having the formula: (b) coupling the 4,4-diphenycyclohexyloxy-dichlorophosphine formed in step (a) with an amine base to obtain 4,4-di-phenyclohexyloxy-diaminophosphine having the formula: (c) coupling the fine 4, 4-diphenyicyloxy diaminophos formed in step (b) with penta ter-butylester of hydroxymethyl-DTPA to obtain 4,4-diphenycyclohexyloxy (penta ter-butyl ester of hydroxymethyl-DTPA- oxy) amino-phosphino having the formula: tBuo tB (d) hydrolysis and oxidation of the 4,4-diphenycyclohexyloxy (penta ter-butylester of hydroxymethyl-DTPA-oxy) -amino-fos formed in step (c) with dilute HCl and an oxidizing agent to form penta t-butylester of [ (4,4-diphenylcyclohexyl) phosphonooxymethyl] diethylenetriamine, having the formula:
15. 15. A process for preparing [(4,4-diphenyl-cyclohexyl) -phosphonooxymethyl] -di-ethyl-ethyl-rimamino-penta-acetic acid comprising the steps of: (a) phosphorylating 1.0 equivalents of 4,4-dipic encyclohexanol with about one equivalent of phosphorus trichloride to obtain 4, 4-dif-en-cyclohexyloxy dichlorophosphine having the formula: (b) coupling the 4,4-diphenycyclohexylaxy-dichlorophosphine formed in step (a) with about 5 to about 6 equivalents of imidazole to obtain 4,4-diphenycyclohexyloxydiimidophosphine having the formula: (c) coupling the 4, 4-diphenylcyclohexy-loxi-diimidophosphine formed in step (b) with about 0.75 to about 1.0 equivalents of tert-butyl ester penta of hydroxymethyl-DTPA to obtain 4, 4-di-phenyclohexyloxy (penta ter- hydroxymethyl-DTPA-oxy,) imido-fos butyl ester having the formula: tB (d) hydrolysis and oxidation of the 4,4-diphenycyclohexyloxy (pent to tert-butylester of hydroxymethyl-DTPA-oxy) fine imidophos formed in step (c) with dilute HCl and from about 0.5 to about 2.0 equivalents of sodium periodate to form penta t-butylester of [(4,4-diphenylcyclohexyl) phosphonooxymethyl] diethylenetriamine, having the formula:
16. 16. The process according to claim 15, characterized in that it further comprises the step of hydrolysis of the penta t-butylester of [(4,4-diphenylcyclohexyl) phosphonooxymethyl] -diethylenetriamine, formed in step (d) in HCl to form acid [( 4, -di feni Icicl ohexi 1) fos fono-oxymeth il] diet ilent riamin penta-acetic having the formula: