GB2161486A - Novel 1-methyl-4,5-dihydroorotic acid derivative and processes for preparing the same - Google Patents

Abstract

1-methyl-4,5-dihydroorotyl-histidyl-prolinamide of the formula: <IMAGE> or a pharmaceutically acceptable salt thereof, processes for their preparation and pharmaceutical compositions containing them. The prolinamide and the pharmaceutically acceptable salts thereof are useful for the treatment of central nervous system disorder.

Description

SPECIFICATION Novel 1-methyl-4,5-dihydro-orotic acid derivative and processes for preparing the same This invention relates to a novel 1-methyl-4,5-dihydro-orotic acid derivative and processes for preparing the same. More particularly, it relates to 1-methyl-4,5-dihydroorotyl-histidyl-prolinamide of the formula:

or a pharmaceutically acceptable salt thereof.

It is known that TRH (i.e., thyrotropin releasing hormone; L-pyroglutamyl-L-histidyl-L-prolinamide) is useful as a medicine for treating consciousness disorders due to a brain dysfunction. In addition to this, however, TRH possesses the TSH (thyroid stimulating hormone)-releasing activity, which is considered to be an undesirable action for its therapeutic effect on the consciousness disorders.

Asa result of various investigations, we have now found that the compound (I) of the present invention shows much stronger activating effects upon the central nervous system (e.g., antagonistic effect on pentobarbital anesthesia, increasing effect of spontaneous locomotor activity, antagonistic effect on reserpine-induced hypothermia, potentiating effect on action of L-Dopa) with less side effects (e.g., TSHreleasing activity) as compared with TRH and is useful as a medicine for the treatment of central nervous system disorders (e.g., consciousness disorder).

According to the present invention, the compound (I) can be prepared for example by condensing 1methyl-4,5-dihydroorotoic acid of the formula:

or a reactive derivative thereof with histidyl-prolinamide of the formula:

or a salt thereof.

Alternatively, the compound (I) can be prepared for example by condensing 1-methyl-4,5-dihydroorotylhistidine of the formula:

or a reactive derivative thereof with prolinamide of the formula:

or a salt thereof.

The starting compounds (III) and (V) may be either in free form or in the form of a salt thereof. Examples of the salt of the compounds (III) and (V) are inorganic acid addition salts e.g. hydrochloride, hydrobromide, sulfate or nitrate, and organic acid addition salts e.g. tosylate, methanesulfonate or trifluoroacetate.

The condensation of the compound (II) or a reactive derivative thereof with the compound (lull) or a salt thereof and the condensation of the- compound- (IV) or a reactive derivative thereof with the compound (V) or a salt thereof can be. accomplished for example in a conventional manner for the synthesis or peptides. For example, the condensation reaction of the reactive derivative of the compound (II) with the compound (III) or a salt thereof and the condensation reaction of the reactive derivative of the compound (IV) with the compound (V) or a salt thereof can be conducted either in the presence or absence of an acid acceptor in a solvent.Examples of-the reactive derivative of the compound (II) or (IV) are the corresponding acid halides (e.g., chloride or bromide), mixed anhydrides (e.g., a mixed anhydride ofthe compound (II or (IV) with alkyl carbonate, active esters (e.g., ester with p-nitrophenol, 2,4-dinitro-phenol, Nhydroxy-succinimide, N-hydroxyphtha limide, I- hydroxybenzotriazole or 1-hydroxy-2-pyrrolidon), acid azide and acid amides (e.g., amide with imidazole, 4-substituted-imidazole or triazole). Dioxane, tetrahydrofuran, acetonitrile, methylene chloride, dimethylformamide, dimethylacetamide, ethyl acetate, pyridine, acetone and water are examples of the solvent.Moreover, examples of the acid acceptor are alkali metal hydroxides (e.g., potassium hydroxide or sodium hydroxide), alkali metal carbonates (e.g., sodium carbonate or potassium carbonate), alkali metal bicarbonates (e.g., sodium bicarbonate or potassium bicarbonate), trialkyl amines (e.g., trimethylamine or triethylamine), N,N- dialkylanilines (e.g., N,N-dimethylaniline or N,N-diethylaniline), pyridine and N-alkylmorpholines (e.g., N-methylmorpholine).It is preferred to carry out the reaction at a temperature of -50"C to 50"C, especially at - 15"C to 5"C, On the other hand, the condensation reaction of the compound (II) in its free form with the compound (III) or a salt thereof and the condensation reaction of the compound (IV) in its free form with the compound (V) or a salt thereof can be conducted for example in the presence of a dehydrating agent in a solvent. Examples of the dehydrating agent are dicyclohexylcarbodiimide, N-cyclohexyl-N'-morpholinocarbodiimide, N-ethyl-N'-(3-dimethylaminopropyl)- carbodiimide, phosphorus oxychloride, phosphorus trichloride, thionyl chloride, oxalyl chloride and triphenylphosphine.Vilsmeier reagent prepared from dimethylformamide and phosphorus oxychloride from dimethylformamide and oxalyl chloride, from dimethyl-formamide and phosgen or from dimethylformamide and thionyl chloride may also be used as said dehydrating agent. It is preferred to carry out the reaction at a temperature of - 50"C to 50"C, especially at -20CC to O"C. Dioxanetetrahydrofuran, acetonitrile, chloroform methylene chloride, dimethylformamide, N,N-dimethylacetamide, ethyl acetate, pyridine, acetone and water are examples of the solvent.

In the above-mentioned reactions, the compounds (if), (Ill), (IV) or (V) may be used in the form of either optically active isomer or a mixture thereof. Since said reactions proceed without racemization, the compound (I) is readily obtained in the form of an optically active isomer by the use of the corresponding opticaliy active isomer of the compound (11), (III), (IV) or (V).

Among the starting compounds, the compound (II) may be prepared for example, by reacting 4,5-dihydro-orotic acid (j. Am. Chem. Soc., 75, 6086 (1953)) with benzyl halide in the presence of an acid acceptor (e.g., triethylamine, N-methylmorpholine or N-methyl- piperidine) in a solvent (e.g., dimethylformamide, ethyl acetate or tetrahydrofuran) at a temperature of -50 C to 50"C, reacting the resulting benzyl 4,5dihydroorotate with methylating agent (e.g., methyl iodide, dimethyl sulfate or methyl trifluoromethanesulfonate) in the presence of an acid acceptor (e.g., sodium hydride, potassium tert.-butoxide, potassium carbonate or sodium hydroxide) in a solvent (e.g., dimethylformamide , tetrahydrofuran, dimethylsulfoxide or acetone at a temperature of -50 C to 500C, and then subjecting the resulting benzyl 1-methyl-4,5dihydroorotate to catalytic hydrogenation in the presence of a catalyst (e.g., palladium-charcoal, pallad ium black or platinum dioxide) iii hydrogen gas atmosphere in a solvent (e.g., tetrahydrofuran, methanol or ethanol) at a temperature of 0 C to 20"C. The compound (IV) may be prepared for example by condensing the compound (II) obtained above with histidine in a conventional manner. Moreover, the histidyl-prolinamide (III) and the prolinamide (V) may be prepared for example according to the method described in Bull. Chem. Soc. Japan, 44 1689 (1971).

While the compound (I) of the present invention can exist in the form of eight optical isomers due to the three asymmetric carbon atoms involved therein, all of the eight optical isomers or a mixture thereof are included within the scope of the invention. Among these isomers, however, 1-methyl-L-4,5-dihydroorotyl-L -histidyl-L-prolinamide is preferred for medicinal use.

The compound (I) can be used pharmaceutically either as the free base or as an acid addition salt thereof. Pharmaceutically acceptable acid additon salts of the compound (I) are, for example, inorganic acid addition salts e.g. hydrochloride, hydrobromide, sulfate or nitrate; and organic acid addition salts e.g. acetate, maleate, tartrate, succinate, citrate, methanesulfonate, malate, oxalate or benzenesulfonate.

These salts may be prepared, for example, by neutralizing the compound (I) with an acid. The compound (I) or a pharmaceutically acceptable acid addition salt thereof may be administered either orally or parenterally. Further, the compound (I) orbits salt may be used in the form of a pharmaceutical preparation containing the same compound in conjunction or admixture with a pharmaceutical excipient suitable for oral or parenteral administration. Suitable excipients are, for example, starch lactose, glucose, potassium phosphate, corn starch, gum arabic, stearic acid or other known medicinal excipient. The pharmaceutical preparation may be in solid form such as, for example, tablets, powders, capsules or granules; or in liquid form such as, for example, solutions or suspensions. Further, when administered parenterally, the pharmaceutical preparation may be used in the form of injections.

As mentioned hereinbefore, the compound (I) of the present invention has much stronger activating effects upon the central nervous system (e.g., antagonistic effect on pentobarbital anesthesia, increasing effect on spontaneous locomotor activity, antagonistic effect on reserpine-induced hypothermia and potentiating effect on action of L-Dopa) with less side effects (e.g., TSH-releasing activity) as compared with TRH. Therefore, the compounds (I) of the present invention are much more useful in palinesthesia, and as spontaneous movement stimulants or dopamine potentiators than TRH.The compounds (I) are also useful for the treatment of central nervous system disorders such as, for example, consciousness disorders, short attention span, speech disorders, hypobulia, Lennox syndrom, senile dementia, hypnotic intoxication, autism, hyperkinesia, schizophrenia, depression and parkinsonism in a warm-blooded animal including human beings.

The therapeutic dose of the compound (I) or its salt depends on the route of administration; the age, weight and condition of patients; and the particular disease to be treated. In general hdwever, it may be used at a dose of 0.5 g to 5 mg per kilogram of body weight per day; especially at a dose of 10 > 9 to 1 mg per kilogram of body weight per day in the case of oral administration; or at a dose of 1ll9 to 100 g per kilogram of body weight'per day in the case of parenteral administration (e.g., intravenously, intramuscularly or subcutaneously).

Practical and presently preferred embodiments of the present invention are illustratively shown below.

Throughout the specification and claims, 1-methyl-4,5-dihydroorotic acid and 1-methyl-4,5-dihydroorotyl mean 1-methyl-i ,2,3,4,5,6- hexahydro-2,6-dioxo-4-pyrimidinecarboxylic acid and 1-methyl- 1,2,3,4,5,6- hexahydro-2,6-dioxo-4-pyrimidine-carbonyl, respectively.

Experiments The pharmacological activities and acute toxicity of a test compound were tested by the following methods.

(Methods) (1) TSH-releasing activity: Seven male JCL:SD rats (6 weeks old) were used in each group. A test compound dissolved in a 0.1 % BSA (bovine serum albumin)- containing physiological saline was intravenously administered to the rats.

Fifteen minutes after the administration, blood was taken from the abdominal aorta under anesthesia.

Serum TSH levels were determined by the double-antibody radioimmunoassay method (Midgley et al., Endocrinology., 79, 10 (1966)). The BSA-containing physiological saline was used for control instead of the test compound solution.

(2) Antagonistic effect on pentobarbital anesthesia: Ten male STD/ddy mice (6 weeks old) were used in each group. Pentobarbital sodium was intraperitoneally administered to the mice at a dose of 55 mg/kg. Ten minutes after the administration of pentobarbital sodium, a test compound dissolved in physiological saline was intravenously administered to the mice which had lost the righting reflex. The duration of anesthesia was measured as the time from the end of administration of the test compound until the righting reflex regained. Psysiological saline was used for control instead of the test compound solution. (Prange et al., Life Science, 14, 447 -455, (1974)) (3) Increasing effect on sponteneous locomotor activity: Five male STD/ddy mice (6 weeks old) were used in each group.The mice were individually placed in an Ambulometer (i.e., an apparatus for measuring spontaneous locomotor activity; manufactured by OHARA IKACo.) for 30 minutes to acclimatize to the apparatus. Thereafter, a test compound dissolved in physiological saline was intraperitoneally administered to the mice and, immediately after administration of the test compound, the spontaneous locomotor activity was measured for 60 minutes. Physiological saline was used for control instead of the test compound solution.

(4) Antagonistic effect on reserpine-induced hypothermia: Five male STD/ddy mice (6 weeks old) having body temperature of 30"C or lower about 17 to 20 hours after subcutaneous administration of reserpine at a dose of 3 mglkg were used in each group. A test compound dissolved in physiological saline was intraperitoneally administered to the mice and the rectal temperature was measured 30, 60, 120 and 180 minutes after the administration of the test compound-.

The increase in temperature in the treated group was compared to that in the control group which received physiological saline instead of the test compound solution.

(5) Potentiating effect on action of L-Dopa: Eight male STUiddy mice (6 weeks old) were used in each group. Reserpine ws subcutaneously administered to the mice at a dose of 3 mgskg and about 16 to 20 hours later L-Dopa was intraperitoneally administered to the mice at a dose of 200 mg.'kg. Thirty minutes after administration of L-Dopa, a test compound dissolved in physiological saline was administered intraperitoneally to the mice (when TRH was used as the test compound, it was administered 45 minutes after administration of L-Dopa). Spontaneous locomotor activity was measured for 15 minutes starting from one hour after administration of L Dopa. Physiological saline was used for control instead of the test compound solution.

(6) Acute toxicity: Ten male STD/ddy mice (6 weeks old) were used in each group. A test compound was intravenously administered to the mice and the acute toxicity (lye., Leo,,0) thereof was determined from mortality 24 hours after administration of the test compound.

Results) The results are shown in the following Tables 1 and 2.

Table I (Pharmacological activities of test compounds) Potency ratio relative to TRHI TRH 1-Meth yl-L-4, 5-dihydroorotyl-L- histidyl-L-prolinamide TSH-releasing activity 1 1130 Antagonistic effect on pentobarbital anesthesia 1 2.7 Increasing effect on 1 27.4 spontaneous locomotor activity Antagonisitc effect on reserpine-induced 1 31.4 hypothermia Potentiating effect on action of L-Dopa 1 18.5 Note: *: Potency ratio relative to TRH was calculated from the dose-response curves of TRH and 1 methyl-L-4,5-dihydroorotyl- L-histidyl-L-prolinamide by the parallel line assay method.

Table 2 (Acute toxicity of test compounds) TRH 1 -Methyl-L-4,5-di hydroorotyl-L- histidyl-L-prolinamide LD50 (mg/kg, i.v.) 1450.:-.-* 1600 Note: *X: Published data (cf. Brain Research Reviews., 4, 389, 1982) Example (1) 5.0 g of L-4,5-dihydroorotic acid are suspended in 80 ml of dimethylformamide, and 4.4 ml of triethylamine and 3.76 ml of benzyl bromide are added thereto. The mixture is stirred at room temperature for 2 days. 6.6 ml of triethylamine and 3.76 ml of benzyl bromide are further added to the mixture, and the mixture is stirred at room temperature for 2 days. The mixture is concentrated under reduced pressure to remove solvent.Water is added to the residue, and the precipitated crystals are collected by filtration, washed with water and then recrystallized from methanol. 5.8 g of benzyl L-4,5-dihydroorotate are obtained.

M.p. 187 -189bC [(Z]r,6 + 56.3 (c = 1, dimethylformamide) NMR (DMSO-d,,)8: 2.6-3.2 (m, 2H), 4.2-4.4 (m, 1H), 5.17 (s, 2H), 7.38 (s, 5H), 7.93 (broad, 1H, 10.16 (s, 1H) (2) 6.6 g of benzyl L-4,5-dihydroorotate are dissolved in 66 ml of dimethylformamide, and 5 ml of methyl iodide are added thereto. 1.29g of sodium hydride (62 % oil dispersion) are added to the mixture at 22 to 28"C, and the mixture is stirred at about 25-C for 40 minutes. Then, the mixture is adjusted to pH 4 with acetic acid, and then concentrated at a temperature below 40"C under reduced pressure to remove dimethylformamide.Ethyl acetate is added to the residue, and the precipitated crystals are collected by filtration, washed with ethyl acetate and then dried. Water is added to the crystals, and the aqueous mixture is stirred for 20 minutes. The crystals are collected by filtration and then recrystallized from ethyl acetate. 3.25 g of benzyl 1-methyl-L-4,5-dihydroorotate are obtained.

M.p. 162 -164-C [(t]2D6 + 51.7 (C = 1, dimethylformamide) NMR (DMSO-d6) 8: 2.6 - 3.3 (m, 2H), 2.95 (s,3H), 4.2 - 4.4 (m, 1H), 5.68 (s, 2H), 7.37 (s, 5H), 8.20 (broad, 1HI (3) 4 g of benzyl 1-methyl-L-4,5-dihydroorotate are dissolved in 80 ml of tetrahydrofuran, and 340 ml of ethanol are added thereto. 0.4 g of 5 % palladium-charcoal is added to the mixture, and the mixture is shaken at room temperature in hydrogen gas atmosphere under an atmospheric pressure. After the reaction is completed, insoluble materials are filtered off.The filtrate is concentrated under reduced pressure to dryness, and the residue is recrystallized from methanol. 1.9 g of 1-methyl-L-4,5-dihydroorotic acid are obtained, M.p. 214 -216"C [nl,2,0 + 49.2 (c = 1, dimethylformamide) NMR (DMSO-d6)8:: 2.5-3.2 (m, 2H), 2.96 (s, 3H), 4.0 -4.2 (m, 1H), 7.9-8.1 (broad, 1H) (4) 1.03 g of 1-methyl-L-4,5-dihydroorotic acid and 760 mg of N- hydroxysuccinimide are dissolved in 20 ml of dimethylformamide, and 1.4 g of dicyclohexylcarbodiimide are added thereto at 0 C. The mixture is stirred at the same temperature for 1.5 hours. 2.8 g of L -histidyl-L-prolinamide dihydrobromide and 2 ml of triethylamine are added to the mixture under cooling, and the mixture is stirred at 0 to 150C for 2 days. Insoluble materials are filtered off, and the filtrate is concentrated under reduced pressure to remove dimethylformamide. The residue is dissolved in dilute hydrochloric acid, and insoluble materials are filtered off.The filtrate is washed with chloroform, alkalized with sodium bicarbonate and then passed through a column packed with styrene-divinylbenzene copolymer resin (manufactured by Mitsubishi Chemical Industries Ltd. under the trademark "MIC GEL CHP-20P"). After the column is washed with 300 ml of water, the desired product is eluted with water. The fractions which are positive to the Pauly's reaction are collected and lyophilized. The product thus obtained is crystallized with water and recrystallized from water to give crystals. The crystals are dried at 60eC under reduced pressure for 3 days. One g of 1- methyl-L-4,5-dihydro-orotyl-L-histidyl-L-prolinamide is obtained.

M.p. 158 -160'?C (decomp.) [ct]D5 -16.40 (c = 1, water) Analysis calculated for C1,H2N7O0.1i2 H2O C, 49.26; H, 5.83; N, 23.66 Found: C, 49.20; H, 5.87; N, 23.97

Claims (6)

1. 1-Methyl-4,5-dihydroorotyl-histidyl-prolinamide of the formula:

or a pharmaceutically acceptable sat thereof.

2. The compound claimed in Claim 1, which is 1-methyl-L-4,5- dihydroorotyl-L-histidyl-L-prolinamide or a pharmaceutically acceptable salt thereof.

3. A process for preparing'1-methyl-4,5-dihydroorotyl-histidyl- prolinamide or a pharmaceutically acceptable salt thereof, which comprises condensing 1-methyl-4,6-dihydroorotic acid or a reactive derivative thereof with histidyl-prolinamide or a salt thereof, and if required further converting the product into a pharmaceutically acceptable salt thereof.

4. A process for preparing 1-methyl-4,5-dihydroorotyl-histidyl- prolinamide or a pharmaceutically acceptable salt thereof, which comprises condensing 1-methyl-4,5-dihydroorotyl-histidine or a reactive dei- vative thereof with prolinamide or a salt thereof, and if required, further converting the product into a pharmaceutically acceptable salt thereof.

5. A pharmaceutical composition which comprises a therapeutically effective amount of 1-methyl-4,5dihydroorotyl-histidyl-prolinamide, or a pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable carrier therefor.

6. 1-methyl-4,5-dihydroorotyt-histidyl-prolinamide or a pharmaceutically acceptable salt thereof, for use as an active theropeutic substance.