SALTS OF ANTIMALARIAL PHENANTHRENEMETHANOL COMPOUNDS

Abstract: Compounds of formula (I) wherein R₁ is hydrogen or an alkyl radical containing one to six carbon atoms; R₂ is an alkyl radical containing one to six carbon atoms; and X is H₂O₃POCH(CH₂OH)₂, n[HO₂CCH(OH) CH(OH)CO₂H] wherein n is 1 / 2 or 1, and 2HO₂CC₆H₇(OH)₄, pharmaceutical compositions containing them and their use as antimalarial agents are described.

Description: SALTS OF ANTIMALARIAL PHENANTHR ENEMET HANOL COMPOUNDS BACKGROUND OF THE INVENTION A number of phenanthrenemethanol compounds have been shown to exhibit antimalarial activity in humans against both chioroquine-sensitive and resistant strains of Plasmodium falciparum. The evaluation of the antimalarial activity of the phenanthrenemethanol, halofantrine or 1- [1,3-dichloro-6-tr ifluoromethyl- 9- phenanthryl] - 3-di - (n-butyl) -aminopropanol hydrochloride, was reported in the American Journal of Tropical Medicine and Hygiene, Vol. 31(6), pages 1075-79 (1982). Halofantrine was effective when administered over a short period of time and with a minimum of two doses against the multi-drug resistant Vietnam Smith strain and Cambodian Buchanan strain of P. falciparum and the Chesson strain of P. vivax. However, problems with systemic bioavailability remained. A means for enhancing the bioavailability of a number of phenanthrenemethanol antimalarial compounds, including halofantrine, utilizing specific organic fatty acids, as adjuvants, has been disclosed in U.S. Patent No. 4,178,376. SUMMARY OF THE INVENTION This invention relates to salts of the class of antimalarial compounds containing halofantr ine (as the free base) and its analogs, and more specifically the (3-glycerophosphate, tartrate and biquinate salts. These salts exhibit markedly increased activity against malariacausing parasites when compared to the hydrochloride salts reported in the literature. Pharmaceutical compositions and methods of treatment of subjects with malaria are also disclosed. DETAILED DESCRIPTION OF THE INVENTION The compounds of this invention represented by the following structural formula (I): EMI2.1 wherein R1 is hydrogen or an alkyl radical containing one to six carbon atoms; R2 is an alkyl radical containing one to six carbon atoms; and X is H203POCH(CH2O n[HO2CCH(OH)CH(OH)CO2Hi wherein n is 1/2 or 1, and 2HO2CC6H7(OH)4, possess markedly increased activity against malaria-causing parasites. A particular class of compounds of this invention are those compounds of formula (I) wherein R1 is an alkyl radical containing one to six carbon atoms, and more particularly wherein both R1 and R2 are n-butyl radicals. Exemplifying this class of compounds are 1- [l,3-dichloro-6-trifluoromethyl-9-phenanthrylI-3-di- (n-butyl)aminopropanol-f3-glycerophosphate, 1- [1, 3-dichloro- 6-trifluoromethyl-9-phenanthryl]-3-di(n-butyl)aminopropanol l/2-tartrate, 1-[1,3-dichloro-6-trifluoromethyl-9- phenanthryl]-3-di (n-butyl)aminopropanol tartrate, and 1-[1,3-dichloro-6-trifluoromethyl-9-phenanthryl]-3-di(n- butyl)aminopropanol biquinate. A second class of compounds of this invention are those compounds of the formula (I) wherein R1 is hydrogen and R2 is a n-butyl radical. Exemplifying this class of compounds is 1- [l,3-dichloro-6-trifluoromethyl-9- phen-anthryl]-3-n-butylaminopropanol-ss-glycerophosphate, 1-[1,3-dichloro-6-trifluoromethyl-9-phenanthryl]-3-n- butylaminopropanol l/2-tartrate, 1- [1, 3-dichloro-6- trifluoromethyl-9-phenanthryl] -3-n-butylaminopropanol tartrate, and 1- [1, 3-dichloro-6-trifluoromethyl-9- phenanthryl]-3-n-butylaminopropanol biquinate. The compounds of this invention are conveniently prepared by reacting ss-glycerophosphoric acid, tartaric acid or quinic acid (1,3,4,5-tetrahydroxycyclohexanecarboxylic acid) with a compound of the formula (II): EMI3.1 wherein R1 and R2 are described above in an inert solvent. The amount of B-glycerophosphoric acid employed in this reaction can be between 0.75 and 1.25 moles per mole of the compound of the formula (II) but equimolar amounts of both reactants are preferred. To prepare the tartrate salts of formula (I), wherein n is 1/2, the amount of tartaric acid employed in the reaction can be between 0.25 and 0.55 moles per mole of compound of the formula (II) but 0.50 moles of tartaric acid is preferred. Similarly, to prepare the tartrate salts of formula (I) wherein n is one, the amount of tartaric acid employed in the reaction can be between 0.75 and 1.25 moles per mole of the compound of formula (II) but equimolar amounts of both reactants are preferred. The amount of quinic acid employed in the above reaction can be between 1.50 and 2.50 moles per mole of the compound of the formula (II) but 2.0 moles of quinic acid is preferred. The compound of formula (II) is mixed with the appropriate amount of acid reactant (50% aqueous solution) and the inert solvent is added to affect solution of the reactants at a temperature selected from the range of ambient temperature to 1000C. The reaction solution is filtered and the filtrate is heated under reduced pressure up to 1000C to remove the solvent. Upon the removal of solvent, the respective compounds of the formula (I) precipitate and are collected and dried. The biquinate salts of formula (I) are partially water soluble to about 20 percent on a weight by weight basis. Examples of the inert solvents which are utilized in the process are alcohols, such as, methanol, ethanol, isopropanol and the like and amides, such as dimethylformamide and dimethylacetamide. The bases of the formula (II) are prepared according to the general procedures described in the Journal of Medicinal Chemistry, Vol. 15, No. 7, pages 771-5 (1972) wherein the process for converting substituted phenanthrene-9-carboxylic acid into the desired compounds as the free base form are detailed. The antimalarial activities of the compounds of this invention is demonstrated in a standard pharmacological in vivo test procedure against P. berghei in Swiss mice. The antimalarial activity of the compounds noted below was established utilizing the following methodology. Test animals were infected by interperitoneal injection of 106 parasitized cells of P. berghei contained in 0.5 ml of 1:400 dilution of donor mouse blood which was infected with P. berghei one week earlier. Three days after infection, 3 groups of 4 mice (2 males and 2 females) were treated with the test compound at a dose level of 1, 4 and 16 mg/kg/day for 4 consecutive days. Similarly, a positive control of 3 groups of 4 mice (2 males and 2 females) were treated with halofantrine, as the hydrochloride salt, at a dose level of 3, 12 and 48 mg/kg/day for 4 consecutive days. The route of administration of the test compound and halofantrine was oral intubation of a suspension of each compound in 0.2% methyl cellulose at a constant volume of 20 ml. A negative control group of 4 mice (2 males and 2 females) remained untreated. The results of the above test procedure (a) measured in survival time in days and percent of red cells parasitized at 28 days in the treated surviving mice and at 3 days in the untreated control mice or (b) expressed as an ED50 (the effective dose which decreases the cell parasitemia by 50 percent on day 4 of treatment) are shown in the following Tables for the noted compounds. Compound A: l-[1,3-dichloro-6-trifluoromethyl-9 phenanthryl]-3-di(n-butyl)aminopropanol-ss-glycerophospate; Compound B: 1- [1, 3-dichloro-6-trifluoromethyl-9- phenanthryl]-3-di (n-butyl)aminopropanol 1/2-tartrate; Compound C: l-[l,3-dichloro-6-trifluoromethyl-9- phenanthryl]-3-di(n-butyl)aminopropanol tartrate; and Compound D: l-[1,3-dichloro-6-trifluoromethyl-9phenanthryl]-3-di(n-butyl)aminopropanol biquinate. TABLE I Dose Deaths - % - Date of Death % Red Cells mg/kg/day x 4 days Parasitized (Mean Value Halofantrine (HC1) 3 mg/kg/day 4/4 - 100% - day 5 12 mg/kg/day 2/4 - 50% - day 8 and 13 16.5% 48 mg/kg/day 0/4 - 0% - 3.0% Compound A 1 mg/kg/day 4/4 - 100% - day 6 to 13 4 mg/kg/day 0/4 - 0% - 0% 16 mg/kg/day 0/4 - 0% - 0% Compound B 1 mg/kg/day 4/4 - 100% - day 5 to 7 4 mg/kg/day 0/4 - 0% - 0% 16 mg/kg/day 0/4 - 0% - 0% Compound C 1 mg/kg/day 3/4 - 75% - day 6 0% 4 mg/kg/day 0/4 - 0% - 0% 16 mg/kg/day 0/4 - 0% - 0% Control 4/4 - 100% - day 4 to 6 71.2% (day 3 TABLE II Dose Number of Animals ED50 Day 4 mg/kg/day x 4 days (Mean Values) Halofantrine (HC1) 1 mg/kg/day 4 6 mg/kg 4 mg/kg/day 4 16 mg/kg/day 4 Compound D 1 mg/kg/day 4 ' 1 mg/kg 4 mg/kg/day 4 16 mg/kg/day 4 Compounds A, B and C are at least 12 times more effective, on a weight by weight basis, in the treatment of P. berghei malaria in mice based on survival times and clearance of parasites when compared to halofantrine hydrochloride. Compound D is at least 6 times more effective, on a weight by weight basis, in the treatment of P. berghei malaria in mice using as an efficacy criterion the ED50 calculation of deparasited cells on day 4 when compared to halofantrine hydrochloride. [See Annals of Tropical Medicine and Parasitology, 73, pp. 505-525, (1979).] The pharmaceutical compositions of this invention containing a compound of formula (I) which has antimalarial activity are prepared in conventional dosage unit forms by incorporating the chemical compound with a nontoxic pharmaceutical carrier according to accepted procedures. A nontoxic quantity of said active ingredient is chosen which is sufficient to produce the desired chemotherapeutic activity in a subject, animal or human, without unacceptable toxicity. The compositions will contain the active ingredient in such an effective but nontoxic amount selected from about 125 mg to about 1000 mg of active ingredient per dosage unit but this quantity depends on the specific biological activity desired, the activity of the compound and the conditions of the patient. A wide variety of pharmaceutical forms can be employed. Thus, if a solid carrier for oral administration is used the preparation can be tableted, placed in a hard gelatin capsule in powder or pellet form, or in the form of a suppository, trouche or lozenge. The amount of solid carrier will vary widely but preferably will be from about 125 mg to about 500 mg. If a liquid carrier is used, the preparation will be in the form of a syrup, emulsion, soft gelatin capsule, sterile injectable liquid such as an ampul, or an aqueous or nonaqueous liquid suspension. The pharmaceutical preparations are made following the conventional technique of the pharmaceutical chemist involving mixing, granulating and compressing when necessary, or variously mixing and dissolving the ingredients as appropriate to give the desired end product. The method of producing antimalarial activity, curatively or prophylactically, comprises administering internally to a subject in need of such activity a compound of formula (I), usually combined with a pharmaceutical carrier, in a nontoxic amount sufficient to produce said activity as described above. The route of administration may be any route which effectively transports the active compound to the site of action which is to be affected within the body such as orally or par enter ally. Advantageously, a single oral dose or equal oral doses will be administered several times such as from 1-3 times a day with the daily dosage regimen being selected from about 125 mg to about 1000 mg. The following examples illustrate the preparations of the compounds of formula (I) and their incorporation into pharmaceutical compositions. EXAMPLE 1 Preparation of l-[1,3-dichloro-6-trifluoromethyl- 9-phenanthryl]-3-di (n-butyl) aminopropanol-ss-glycerophosphate (Compound A) To a 50% aqueous solution of ss-glycerophosphoric acid (4.8 g) at ambient temperature with stirring was added 1- [-l,3-dichloro-6-trifluoromethyl-9-phenanthryl]-3- di (n-butyl)aminopropanol (14.0 g). To the mixture was added ethanol (500 ml) and the mixture is heated to about 1000C to affect solution. The solution is then filtered and the ethanol removed under vacuum until the desired product precipitates as a white crystalline material. After collecting and drying, the desired product has a melting point of 60-650C. Elemental analysis is as follows: Calculated C, 51.78; H, 5.80; N, 2.08 and C1, 10.56 Found C, 51.83; H, 5.65; N, 2.10 and C1, 10.20. EXAMPLE 2 Preparation of 1- [1,3-dichloro-6-trifluoromethyl- 9-phenanthryl]- 3-di (n-butyl)aminopropanol 1/2-tar trate (Compound B) To a 50% aqueous solution of tartaric acid (1.35 g) at ambient temperature with stirring was added 1- [-1,3-dichloro-6-trifluoromethyl-9-phenanthryl]-3- di(n-butyl)aminopropanol (9.0 g). To the mixture was added ethanol (500 ml) and the mixture is heated to about 1000C to affect solution. The solution is then filtered and the ethanol removed under vacuum until the desired product precipitates as a white crystalline material. After collecting and drying, the desired product has a melting point of 1580C. Elemental analysis is as follows: Calculated C, 58.43; H, 5.77; N, 2.43 and C1, 12.34 and F, 9.91. Found C, 58.51; H, 5.40; N, 2.31; C1, 11.99 and F, 9.70. EXAMPLE 3 Preparation of l-[l,3-dichloro-6-trifluoromethyl- 9-phenan thryl] - 3-di (n-.butyl) aminopr opanol tar tr ate (Compound C) Utilizing the general procedure of Example 2 with 2.7 g tartaric acid and 9.0 g of l-[1,3-dichloro-6- trifluoromethyl- 9-phenanthryl] - 3-di (n-butyl) aminopropanol afforded the desired product as a white crystalline material with a melting point of 75-800C. Elemental analysis is as follows: Calculated C, 55.38; H, 5.53; N, 2.15; C1, 10.92 and F, 8.77. Found C, 54.92; H, 5.50; N, 2.00; C1, 11.30 and F, 8.95. EXAMPLE 4 Preparation of 1- [1, 3-dichloro-6-trifluoromethyl- 9-phenanthryl]-3-di (n-butyl)aminopropanol biquinate (Compound D) To a 50% aqueous solution of quinic acid (4.62 g) at ambient temperature with stirring was added 1- [-1,3dichloro- 6-trifluoromethyl-9-phenanthryl]-3-di (n-butyl) aminopropanol (6 g). To the mixture was added ethanol (500 ml) and the mixture is heated to about 100C to affect solution. The solution is then filtered and the ethanol and water removed under vacuum until dryness. The desired product solidifies as a white crystalline material with a melting point of about 900C and is soluble in water up to 20 percent on a weight to weight basis. Elemental analysis is as follows: Calculated C, 54.29; H, 6.32; N, 1.58 and C1, 8.03; F, 6.44. Found C, 54.32; H, 6.24; N, 1.66 and C1, 7.95; F, 6.49. EXAMPLE 5 As specific embodiments of compositions of this invention, an active ingredient, such as one part of Compound A, B, C or D is dissolved in 20 parts of 0.2 percent aqueous methyl cellulose and is administered orally in one dose of 4 mg/kg to a subject in need of treatment of malaria.

Claims: FOR: BE, FR, DE, IT, LI, LU, NE, SE, CH, UK. CLAIMS: 1. A compound represented by the following structural formula (I): EMI11.1 wherein R1 is hydrogen or an alkyl radical containing one to six carbon atoms; R2 is an alkyl radical containing one to six carbon atoms; and X is H203POCH(CH2OH) 2 nHO,CCH(OH)CH(OH)Cij2H] wherein n is 1/2 or 1, and 2H02CC6H7(OH)4. 2. A compound of claim 1 wherein R1 is an alkyl radical containing one to six carbon atoms. 3. A compound of claim 2 wherein both R1 and R2 are n-butyl radicals. 4. A compound of claim 3 which is 1-[1,3dichloro-6-trifluoromethyl-9-phenanthryl]-3-di(n-butyl) aminopropanol-R-glycerophosphate, l-[1,3-dichloro-6- trifluoromethyl-9-phenanthryl] -3-di(n-butyl) aminopropanol hemitartrate, 1- [1,3-dichloro-6-trifluoromethyl-9 phenanthryl] -3-di (n-butyl) aminopropanol monotartrate, or 1-[1,3-dichloro-6-trifluoromethyl-9-phenanthryl] -3-di(nbutyl) aminopropanol biquinate. 5. A compound of claim 4 in a solid form. 6. A compound of claim 1 wherein R1 is hydrogen. 7. A pharmaceutical composition comprising a compound as claimed in any one of claims 1 to 6 and a pharmaceutically acceptable carrier therefor. 8. A compound as claimed in any one of claims 1 to 6 for use as a therapeutic agent. 9. A compound as claimed in claim 8 for use as an antimalarial agent. 10. A process for the preparation of a compound as claimed in any one of claims 1 to 6 which comprises reacting the appropriate amount of ss-glycerophosphoric acid, tartaric acid or quinic acid with a compound of the formula (it): EMI12.1 wherein R1 and R2 are as defined in claims 1, 2, 3 or 6 in an inert solvent. CLAIMS FOR THE DESIGNATED STATE AT CLAIMS:- 1. A process for the preparation of a compound represented by the following structural formula (I): EMI13.1 wherein R1 is hydrogen or an alkyl radical containing one to six carbon atoms; R2 is an alkyl radical containing one to six carbon atoms; and X is H203POCH(CH20H) 2 n[HO2CCH(OH) CH(OH).CO2H] wherein n is 1/2 or 1, and 2H02CC6H7(OH)4, which comprises reacting ss-glycerophosphoric acid, tartaric acid or quinic acid with a compound of the formula (II): EMI13.2 wherein R1 and R2 are as defined above, in an inert solvent. 2. The process of claim 1 wherein equimolar amounts of ss-glycerophosphoric acid and a compound of the formula (II) are employed. 3. The process of claim 1 wherein equimolar amounts of tartaric acid and a compound of the formula (II) are employed. 4. The process of claim 1 wherein 0.50 moles of tartaric acid and 1.0 mole of a compound of the formula (II) are employed. 5. The process of claim 1 wherein 2.0 moles of quinic acid and 1.0 mole of a compound of the formula (II) are employed. 6. A process as claimed in any one of claims 1 to 5 in which the product is l-[1,3-dichloro-6-trifluoro- methyl-9-phenanthryl]-3-di(n-butyl)aminopropanol-ss- glycerophosphate, l-[1,3-dichloro-6-trifluoromethyl-9- phenanthryl]-3-di(n-butyl)aminopropanol hemitartrate, 1-[1,3-dichloro-6-trifluoromethyl-9-phenanthryl]-3-di(nbutyl)aminopropanol monotartrate, or l-[1,3-dichloro-6- trifluoromethyl-9-phenanthryl] -3-di (n-butyl) aminopropanol biquinate, and the product is Isolated as the solid particulate salt. 7. A process for the preparation of a pharmaceutical composition which comprises bringing into association a compound of structure (I) as defined in claim 1 and a pharmaceutically acceptable carrier therefor. 8. A process according to claim 7 in which the compound of structure (I) is 1-[1,3-dichloro-6-trifluoro- methyl-9-phenanthryl]-3-di(n-butyl) aminopropanol-ss- glycerophosphate, l-[1,3-dichloro-6-trifluoromethyl-9- phenanthryl] -3-di (n-butyl) aminopropanol hemitartrate, 1-[1,3-dichloro-6-trifluoromethyl-9-phenanthryl]-3-di(nbutyl)aminopropanol monotartrate, or l-[1,3-dichloro-6 trifluoromethyl-9-phenanthryl] -3-di (n-butyl) aminopropanol biquinate.

Inventors: ROSSIGNOL, JEAN FRANCOIS
Applicants: SMITHKLINE BECKMAN CORPORATION
Application year: 1984
Main classification: C07C91
IPC codes: C07F9, C07D453