HU211271A9 - New optical isomers - Google Patents

Description

New optical isomers

The present invention relates to novel optical isomers of 4- (5-fluoro-2,3-dihydro-1H-inden-2-yl) -1H-imidazole, to pharmaceutically acceptable salts thereof, and to the use and preparation of said compounds. Both optical isomers are effective in the treatment of cognitive disorders, although with slightly different pharmacological profiles. Of the two isomers, the (-) - enantiomer is preferred because it has a broader therapeutic application than the (+) - enantiomer. so extremely strong antagonistic activity is ₂ adrenoceptor Candidate regards any ct | -agonizmus without, however, the (+) - enantiomer only moderately antagonistic activity is ₂ adrenoceptor respect, while fully _r agonist. Both enantiomers have good oral bioavailability.

For example, European Patent Application Nos. 183,492,247,764 and 372,954 previously disclosed valuable _2- adrenoceptor antagonists. PCT Publication No. 91/18886 discloses the use of certain indanimidazole derivatives, in particular atipamezole, for the treatment of age-related memory impairment and other cognitive disorders. International patent application PCT / FI92 / 00349 discloses a group of novel, long-acting 4- (5) substituted indanimidazole derivatives which can be used in the treatment of cognitive disorders. One of these indanimidazole derivatives is the racemate of 4- (5-fluoro-2,3-dihydrolH-inden-2-yl) -1H-imidazole, which contains an asymmetric carbon atom at the 2-position of the indane ring, as in ( It follows from formula (I).

Optically active enantiomers of 4- (5-fluoro-2,3-dihydro-1H-inden-2-yl) -1H-imidazole can be prepared, for example, by racemic 4- (5-fluoro-2,3-dihydro- 1H-Inden-2-yl) -1H-imidazole is converted into a mixture of diastereoisomers and then separated by fractional crystallization. Given that 4- (5-fluoro-2,3-dihydro-1H-inden-2-yl) -1H-imidazole is a base, it can be converted into a mixture of diastereomeric salts with an optically active acid, preferably L - (+) - or D. - (-) - by reaction with boric acid. The diastereoisomers may be separated by repeated crystallization, for example from water.

After separation of the diastereomers, the acid addition salts can be converted back to the free bases by basifying their aqueous solution with a base such as sodium hydroxide and then extracting the liberated base with a suitable organic solvent.

The (-) - and (+) - enantiomers of 4- (5-fluoro-2,3-dihydro-1H-inden-2-yl) -1H-imidazole react with organic or inorganic acids to form the corresponding acid addition salts, which are the same therapeutic salts. and enantiomers, such enantiomers have a variety of pharmaceutically acceptable acid addition salts such as chlorides, bromides, sulfates, nitrates, phosphates, sulfonates, formals, tartrates, maleates, citrates, benzoates. may form salicylates and ascorbates.

The racemate of 4- (5-fluoro-2,3-dihydro-1H-inden-2-yl) -1H-imidazole can be prepared, for example, by 4- (2,3-dihydrolH-inden-2-yl) -1H- the imidazole hydrochloride is nitrated with a strong nitrating agent such as urea nitrate in the presence of sulfuric acid and the nitro compound is reduced to the corresponding amino compound, for example by catalytic hydrogenation, using platinum dioxide or palladium on carbon as the catalyst. The amino-substituted compound can then be further converted to the corresponding diazonium fluoroborate with sodium nitrite in fluoroboric acid at reduced temperature. The diazonium fluoroborate is then thermally degradable to the racemate of α4- (5-fluoro-2,3-dihydro-1H-inden-2yl) -1H-imidazole. The compounds of the invention may be administered enterally or parenterally. For the treatment of cognitive disorders, the preferred daily dose is between 0.1 mg / kg and 10 mg / kg, most preferably between 0.2 mg / kg and 1 mg / kg.

Acute toxicity (LD ₁₀ ) for both enantiomers is about 100 mg / kg orally in mice and about 50 mg / kg in rats.

The pharmaceutical excipients typically used with the compound of the invention may be solid or liquid and will be selected depending on the intended route of administration. The choice of excipients for pharmaceutical formulations is a routine task for those skilled in the art.

/. α-adrenoceptor selectivity in vitro

O 1 antagonism is determined on the electrically stimulated prostatic part of an iron deferens preparation isolated from rats [Virtanen et al., Arch. Int Pharmacodyn et Ther. 297: 190-204 (1989)]. In this method, the _2- agonist (detomidine) blocks electrically stimulated muscle contractions and the effect of the _2- antagonist can be determined by administering the agonist before and then determining the pA _{2 value} . Atipamezole, a known _2- antagonist, is used as reference substance.

In order to obtain information on the selectivity of a particular antagonist between α _{1 and} β ₂ receptors, its ability to inhibit or stimulate α 1 receptors is determined, particularly in the isolated adrenal gland of iron deferens. In order to determine α, antagonism, muscle-contraction is induced with phenyl effin and the pA _{2 of} the test compound is determined as described above. The 5-agonist effect is expressed as pD ₂ (the negative logarithm of the molar concentration of the test compound which produces 50% of the maximum contraction). Table 1 shows the results obtained.

Table I Race'm

Selectivity of 4- (5-fluoro-2,3-dihydro-1H-inden-2-yl) -1H-imidazole and its enantiomers compared to atipamezole

Test compound number- U ₂ antagonism (pA ₂ detominin) cq antagonism (pA against _2-phenyl efrinnel) aj agonism (pD ₂ ) (-) - enantiomer " mer 9.1 6.7 no effect (+) - enaniio- mer 7.9 has not been measured 6.0 total agonist

HU 211 271 A9

Test compound number- Ctj antagonism (pAj to detomidine) Otj antagonism (pAj against phenylephrine) agonism _r (p2) racemate 8.0 has not been measured 5.5 partial agonist atipamezole 8.0 5.0 no effect

2. Memory effect

The effect of (-) - enantiomers on learning and memory in rats is studied in a linear maze task. A modified version of the linear maze is the radial array maze commonly used to test memory in rats. (-) - Enantiomeric hydrochloride (0.1 mg / kg subcutaneously) is dissolved in distilled water. Distilled water is also used as a control. Each injection is given in a volume of 1 ml / kg.

Experimental equipment: The maze base is made of wood and has the shape of two interconnected crosses. The handle of the maze (initial section) is 90 cm long and 12 cm wide. The other five sections of the maze (target sections) are 50 cm long and 12 cm wide. Four target segments are perpendicular to both the starting and the fifth destination segments facing each other. Each side of the handle and target sections is bounded by a 2 cm edge. At the end of each target section is a hole 1 cm deep, 3 cm in diameter, which serves as a feeder. The start piece (20x20 cm) is separated from the neck by a guillotine door. The door is 12 cm high, 7 cm wide. The door frame is 20 cm high, 20 cm wide. The maze is located 31 cm above the floor in a low-lit experimental room that contains objects other than the experimental equipment. At the end of the target sections, 3 pellets (45 mg pellets, Bio Serve Inc. products) were placed as rewards.

Procedure: During the two days prior to training, the animals are deprived of food, resulting in a reduction to 90% of the initial weight. On these days, we train the animals (three times a day) and get used to the experimental room and reward food. On the second day, acclimatize to the empty maze by placing 3-5 animals from the same cage at the same time for 10 minutes. On the third day, the target section feeder is filled with a food reward and the learning test (one animal at a time) is performed. The rat is placed in the starter unit 60 minutes after administration of the drug or distilled water. After 10 seconds, we open the door and the rat can explode in the maze until he finds the food reward. During the experiment, re-enters into already-targeted target sections are counted as errors. Note the time taken to find all the food rewards and make the right choices until the first mistake is made. During this phase of learning, each animal can spend at least 5 minutes in the maze. The actual test of memory and learning begins on the following day and continues for four days (Experiment Day 1-4). Rats are tested 8 times each, two daily. The interval between rehearsals is 50 minutes. The active ingredient or desulphurized water is administered 30 minutes before the start of the first test of that day. In all other respects, the test tests correspond to the teaching test. There are 20 animals in each group.

Statistical Processing: Results are expressed as mean error / trial, average correct choice / trial, and mean time / trial (seconds). Multivariate analysis of variance (ANOVA) was used to compare the effect of the drug and the test day on learning and memory.

Results: The effects of (-) enantiomers on learning and memory are shown in Figures 1, 2 and 3. The drug resulted in a reduction in the number of errors, ie a reduction in the number of re-visits to the target sections already visited (Figure 1). The (-) - enantiomer also increases the number of correct choices before the first error in the experiment (Figure 2). Based on these, the effect of the active substance on working memory and ability to concentrate during the experiment can be assumed. The active ingredient also tends to reduce the time required to complete the task (Figure 3). This is considered to have an impact on the time needed to make decisions, in this case the right choices. The number of errors and the time spent on solving the task decreased, and the number of correct choices increased from experiment to experiment in the control group, indicating the learning effect during the experiments. Statistical analysis shows no group versus day interaction, which means that the effect of the (-) - enantiomer is independent of the experiment. These results suggest that the (-) enantiomer stimulates learning and memory in adult rats.

3. Preparation of optically active isomers

Racemic 4- (5-fluoro-2,3-dihydro-] H -inden-2-yl) -1H-imidazole was cooled to -10 DEG C. and 13.8 g (0.0625 moles) of 4- (2,3-Dihydro-1H-inden-2-yl) -1H-imidazole hydrochloride (U.S. Patent No. 4,689,339 to Karjalainen, AJ et al.) And 7.70 g (0.0625 mol). urea nitrate mixture in small portions -10 'Con. After the reaction is complete, the solution is poured onto ice. The solution was made alkaline and extracted three times with ethyl acetate. The organic extracts were combined, dried and evaporated to dryness. There was thus obtained 4- (2,3-dihydro-5-nitro-1H-inden-2-yl) -1H-imidazole (13.0 g).

4- (2,3-Dihydro-5-nitro-1H-inden-2-yl) -1H-imidazole 4- (5-amino-2,3-dihydro-1H-inden-2-yl) -1 Reduction to H-imidazole by adding a solution of 11.7 g (0.0512 mol) of 4- (2,3-dihydro-5-nitro-1H-inden-2-yl) -1H-imidazole in 100 mL of ethanol 1.0 g of 10% palladium-on-carbon and the mixture is shaken under a hydrogen atmosphere at room temperature. When the reduction is complete, the catalyst is removed. The filtrate was evaporated3

A9 gave 9.63 g (94%) of 4- (5-amino-2,3-dihydro-1H-inden-2-yl) -1H-imidazole. The product was purified by flash chromatography eluting with methylene chloride / methanol (9.5: 0.5).

A flask containing 120 ml of a 48% w / w aqueous solution of fluoroboric acid and 9.50 g (0.0475 mol) of 4- (5-amino-2,3-dihydrolH-indene-2) was placed in an ice-salt bath. -yl) -1H-imidazole and then cooled to 0 ° C. A solution of sodium nitrite (3.30 g, 0.0478 mol) in water (10 ml) was added slowly while maintaining the temperature at 0 ° C. The reaction mixture was then stirred at 0 ° C for an additional hour and then at room temperature for an additional hour. The reaction mixture was then evaporated twice to dryness with toluene. The decomposition is performed in a flask heated with an electric heating jacket. When the white fumes of boron trifluoride have ceased, heating is stopped. The crude product was dissolved in methanol, filtered and evaporated to dryness. The yield of crude 4- (5-fluoro-2,3-dihydro-1H-inden-2-yl) -1H-imidazole was 9.51 g (99%). The product was purified by flash chromatography using methylene chloride / methanol (9.5: 0.5) as eluent.

1 H-NMR (300 MHz, CD 3 OD): δ 2.96-3.08 (2H, m, one H-1 and one H-3), 3.19-3.27 (2H, m, another

H1 and another H-3), 3.68 (1H, quintet, ^3, HH 8.3)

Hz, H-2), 6.80-6.86 (1H, m, H-6), 6.83 (1H, s, im-5), 6.92 (1H, dd, ^3J HF 8.9 Hz, ^4J HH 2.4 Hz, H-4), 7.16 (1H, dd, ^3J HH 8.1 Hz, ^4, HF 5.3 Hz, H-7), 7.59 (1H, s, im- 4)

Separation of Enantiomers At 0 ° C, D-(-) - tartaric acid (0.44 g, 0.0293 mol) was dissolved in 2.5 ml of water. To the solution is added 1.03 g (0.00509 mol) of the racemate of 4- (5-fluoro-2,3-dihydro-1H-inden-2-yl) -1H-imidazole (I) at 60 ° C. 178 pl concentrated hydrochloric acid. The reaction mixture was stirred at 60 ° C until a clear solution was obtained. The solution was allowed to cool slowly. The precipitate was collected and recrystallized five times from water to give the (-) enantiomers, m.p. 186-187 ° C with D - (-) - tartaric acid.

The D - (-) - tartaric acid adduct of the (-) enantiomer was dissolved in water at 60 ° C and ethyl acetate was added. The solution is then made basic (pH 10) with dilute sodium hydroxide solution. The ethyl acetate layer was separated and the aqueous layer was extracted twice with ethyl acetate. The combined organic phases are washed with water. The ethyl acetate is evaporated to dryness and the residue is crystallized from ethyl acetate. The product was filtered off with suction and washed with cold ethyl acetate. Melting point 139 'C (DSC), specific rotation at -20' C in methanol solution -3.7 '(c = 20 mg / ml).

The (-) - enantiomeric base is dissolved in ethyl acetate and filtered using Millipore. The filtrate was acidified (pH 1) with anhydrous hydrochloric acid in ethyl acetate and cooled to -10 ° C. The precipitate was filtered off with suction and washed with ethyl acetate. Recrystallization from ethyl acetate gave the hydrochloride salt of (-) - 4- (5-fluoro-2,3-dihydrol-1H-inden-2-yl) -1H-imidazole as a white crystalline solid, m.p. 191 ° C (DSC): chromatographic purity 99.8% (HPLC); 99.9% optical purity (HPLC); specific rotation at room temperature in aqueous solution -3.5 '(c = 20 mg / ml).

The (+) enantiomer can be resolved in the same way as the (-) isomer using L - (+) - tartaric acid as the resolving agent when the (+) - enantiomer is formed with the L - (+) - tartaric acid adduct of melting point 187-189 ° C. is obtained. The base and the hydrochloride salt (m.p. 190 'C) were prepared as described above. The chromatographic purity of the hydrochloride salt was 98.7% (HPLC); 99.6% optical purity (HPLC); specific rotation at room temperature in aqueous solution, +3.2 '(c = 20 mg / ml).

Claims (9)

CLAIMS 1. A (-) - enanomer of 4- (5-fluoro-2,3-dihydro-1H-inden-2-yl) -1H-imidazole and pharmaceutically acceptable salts thereof. 2. A process for preparing the (-) - enantiomer of 4- (5-fluoro-2,3-dihydro-1H-inden-2-yl) -1H-imidazole, characterized in that the racemic 4- (5-fluoro-2,3 -dihydro-1H-inden-2-yl) -1H-imidazole is converted to a diastereomeric salt mixture by reaction with an optically active acid, and then the mixture of the diastereomeric salt is separated by fractional crystallization and the 4- (5-fluoro-2,3-dihydro- The separated (-) - enantiomeric salt of lHinden-2-yl) -1H-imidazole is converted to the free base. Process according to claim 2, characterized in that the optically active acid is D - (-) - tartaric acid. 4. The (+) - enantiomer of 4- (5-fluoro-2,3-dihydro-1H-inden-2-yl) -1H-imidazole and pharmaceutically acceptable salts thereof. 5. A process for preparing the (+) - enantiomer of 4- (5-fluoro-2,3-dihydro-1H-inden-2-yl) -1H-imidazole, characterized in that racemic 4- (5-fluoro-2,3) -dihydro-1H-inden-2-yl) -1H-imidazole is converted to a diastereomeric salt mixture by reaction with an optically active acid, and then the mixture of the diastereomeric salt is separated by fractional crystallization and the 4- (5-fluoro-2,3-dihydro- The separated (+) - enantiomeric salt of lHinden-2-yl) -1H-imidazole is converted to the free base. 6. The process of claim 5, wherein the optically active acid is L - (+) - tartaric acid. 7. A novel compound essentially as described herein. 8. A novel process for the preparation of a compound, essentially as described herein. 9. A novel method for the separation of an enantiomer, essentially as described herein.