BG100218A - Enantiomers of 4-(5- fluoro-2,3-dihydro-1h-inden-2-yl)-1h-imidazole - Google Patents

Abstract

The invention relates to optical isomers of 4- (5-fluoro-2,3-dihydro-1 H -inden-2-yl) -1H-imidazole, to their pharmaceutically acceptable salts and their use and preparation. Both isomers are active in the treatment of cognitive impairment.

Description

The invention relates to novel optical isomers of 4- (5-fluoro-2,3-dihydro-1H-inden-2-yl) -1H-imidazole and its pharmaceutically acceptable salts, use and preparation thereof. Both optical isomers are active in treating cognitive impairment, although some other pharmacological profiles may be attributed to them. (-) - The enantiomer is the preferred of the two enantiomers as it has a wider therapeutic range than the (N -) - enantiomer. It is powerful antagonist and ₂ adrenergic receptors without any α, -agonizam, while the (+) enantiomer is a moderate antagonist and ₂ adrenergic receptors and full α, agonists. Both enantiomers have good oral bioavailability.

Valuable _{a2-adrenoceptor} antagonists are described pore, for example, in EP № 183 495, 247 764 and 372 954. In PCT patent publication № 91/18886 discloses the use of some indan-imidazole derivatives, especially atipamezole for the treatment of related age memory impairment and other cognitive abilities. International Patent Application PCT / FI 92/00349 describes a group of novel long-acting 4 (5) substituted indan-imidazole derivatives that are useful for treating cognitive impairment.

The indan-imidazole derivative is also the 4- (5-fluoro-2,3-dihydro-1H-inden-2-yl) -1H-imidazole racemate according to the present invention, which has an asymmetric carbon atom at the 2 position in the indane ring:

The optically active enantiomers of 4- (5-fluoro-2,3dihydro-1H-inden-2-yl) -1H-imidazole can be obtained, for example, by conversion of racemic 4- (5-fluoro-2,3dihydro-1H -inden-2-yl) -1H-imidazole in a mixture of diastereoisomers and separated by fractional crystallization. Because 4- (5-fluoro-2,3-dihydro-1H-inden-2-yl) -1H-imidazole is a base, it can be converted into a mixture of diastereoisomeric salts by reaction with an optically active acid, preferably with L - (+) - or O - (-) - tartaric acid. The diastereoisomers may be separated by recrystallization, for example from water.

After separation of the diastereoisomers, the acid addition salts can be converted to the free bases again, their aqueous solutions alkalized with a base (eg sodium hydroxide) and the liberated base extracted into a suitable organic solvent.

The (-) - and (+) -enantiomers of 4- (5-fluoro-2,3-dihydro-1 Ninden-2-yl) -1H-imidazole are reacted with organic or inorganic acids to form the corresponding • · · ·

acid addition salts having the same therapeutic activity as the bases. Thus, many pharmaceutically useful acid addition salts such as chlorides, bromides, sulfates, nitrates, phosphates, sulfonates, formates, tartrates, maleates, citrates, benzoates, salicylates and ascorbates can be formed.

The racemate 4- (5-fluoro-2,3-dihydro-1H-inden-2-yl) -1 Nimidazole can be prepared, for example, by nitration of 4- (2,3-dihydro-1H-inden-2-yl) -1H-imidazole hydrochloride with a strong nitrating agent such as nitrourea in the presence of sulfuric acid and then reducing the nitro compound to the corresponding amino compound, for example by catalytic hydrogenation using PtO ₂ or Pd / C as a catalyst. The amino substituted compound is then converted to the corresponding diazonium fluoroborate with sodium nitrite in fluoroboric acid at reduced temperature. Diazonium fluoroborate is then thermally decomposed to give the racemate 4- (5fluoro-2,3-dihydro-1H-inden-2-yl) -1H-imidazole.

The compounds of the invention may be administered enterally or parenterally. In the treatment of cognitive impairment, the preferred daily dose is from 0.1 to mg / kg, especially preferably from 0.2 to 1 mg / kg.

The acute toxicity (LD ₆₀ ) for both enantiomers is about 100mg / kg in mice (p.o.) and about 50 mg / kg in rats.

The pharmaceutical carriers commonly used with the compound of the invention may be solid or liquid and selected in accordance with the intended mode of administration in memory. The choice of auxiliary ingredients for the formulation is a routine operation for those skilled in the art.

EXAMPLE 1. α-Adrenoceptor selectivity in vitro a ₂ -Antagonism is determined by an isolated, electrically stimulated preparation of rat prostate vas deferens (Virtanen et al, Arch. int. Pharmacodyn et Ther., 297, 190-204, 1989). In this model, _two -agonistat (detomidine) blocks electrically stimulated muscular contractions and the effect of a ₂ -antagonista seen in its application immediately prior to the agonist and by determining its pA ₂ value. The known _{a2-antagonist} atipamezole was used as reference substance.

To obtain information also on the selectivity of the antagonist between a, - and _a2 -receptors, its ability to inhibit or stimulate α, receptors was determined by means of isolated epididymal portion of rat vas deferens of. In order to determine α-antagonism, muscle contraction was induced by phenylephrine and the pA ₂ value of the test compound was determined as above. The α-agonist effect is presented as a pD ₂ value (negative logarithm of the molar concentration of the compound causing 50 percent of maximal contraction). The results are given in Table 1.

Table 1

Selectivity of racemic 4- (5-fluoro-2,3-dihydro-1H-inden-2yl) -1H-imidazole and its enantiomers in comparison with atipamezole

Compound and _{2 is} antagonism α, -antagonism α, -agonism (pA ₂ values (pA ₂ values (PD ₂ ) detomidine) phenylephrine) (-) - Enantiomer 9,1 6,7 no effect 6.0 (+) -enantiomer 7.9 not tested a complete agonist 5.5 the racemate 8.0 not tested partial agonist atipamezole 8.0 5.0 no effect

EXAMPLE 2. Effect on memory

The effect of the (-) - enantiomer on learning and memorization was investigated by rat experiments in a linear corridor maze. The linear corridor maze is a modified version of the radial corridor maze, which is the most commonly used memory test in rats, (-) - the entantiomer hydrochloride (0.1 mg / kg subcutaneously) is dissolved in distilled water. Water is also used as a control. All injections are made in a volume of 1 ml / kg.

Apparatus: The maze is made of a wooden platform with two intersections one after the other. The main (initial • · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · (Corridor) is 90 cm long and 12 cm wide. The other five corridors (destination corridors) are 50 cm long and 12 cm wide. Four of the destination corridors are perpendicular to the main corridor and the fifth corridor, which is located on the opposite side of the main corridor. There are 2 cm high edges on each side of the main corridor and the branches. At the end of each destination corridor, an opening 1 cm deep and 3 cm in diameter serves as a food container. The starting platform (20/20 cm) is separated from the main corridor by a falling door. The door is 12 cm high and 7 cm wide. The door frame is 20 cm high and 20 cm wide. The labyrinth is raised 31 cm above the floor in a dimly lit test room that contains objects other than test equipment. At the end of the destination corridors is a bait consisting of 3 food-bait tablets (45 mg Bio Serve Inc. tablets).

Methodology: Two days before training, animals are deprived of food for a period that reduces their body weight to 90% of their initial weight. These days, rats are trained to handle (three times a day) experimental space and food bait. On the second day, they are also trained to lure without a lure: 3 to 5 animals per cell at a time for 10 minutes. On the third day, the target corridors are provided with bait and an attempt is made to train one rat for a selected time. The rat received medication or distilled water and was placed on the launch platform 60 minutes later. After 10 seconds, the door opens and the rat is allowed to explore the maze until it has found all the baits. Re-entrances to a corridor previously visited during a session are reported as errors. The time to find all the baits and the correct choice made until the first mistake is logged. During this time (training), each rat is left in the maze for at least five minutes. The next day, the study of one's own memory and learning ability began, and lasted four days (test days 1 to 4). The rats were subjected to 8 experiments, two per day. Trial intervals are 50 min. The medicine or distilled water is given 30 minutes before the first attempt of the day. In other words, the research attempts are identical to the training attempts. There are 20 animals in both groups.

Statistical analysis: The results are expressed as the average number of trial errors, the average number of correct choices for the trial, and the average trial time (sec.). The Re-Measurement Analysis (ANOVA) analysis is used to compare the effects of the drug and the day of the trial on training ability and memory.

Results: The effects of the (-) - enantiomer on learning ability and memory are presented in FIG. 1,2 and

3. The drug reduces the number of errors, ie. re-entry into the corridors already visited during the same attempt (Fig. 1). (-) - The enantiomer also increases the number of correct choices made before the first error in the experiment (Figure 2). This is thought to imply an effect on working memory and the ability to concentrate on experience, respectively. The medication also leads to a reduction in the time to solve the problem (Fig. 3). This is considered as an impact on the speed of decision in the case of the right choice. The number of errors and time decreases, and the number of correct choices increases with each experience, which indicates training in the control group as well. There is no group x of interaction between experiments, which means that the effect of the (-) - enantiomer is independent of experience. These results indicate that the (-) - enantiomer has effects on enhancing training and memory in adult rats.

EXAMPLE 3. Preparation of Optically Active Isomers

Racemic 4- (5-fluoro-2,3-dihydro-1H-inden-2-yl) -1 Nimidazole

Concentrated sulfuric acid (58 ml) was cooled to -10 ° C and 4- (2,3-dihydro-1H-inden-2-yl) -1H-imidazole hydrochloride was added (Karjalainen, AJ et al US 4 689 339, 13.8 g, 0.0625 mol) and nitrourea (7.70 g, 0.0625 mol) in small portions to the acid solution at -10 ° C. After the reaction, the solution is poured into ice. The solution was basified and extracted three times with ethyl acetate. The organic extracts were combined, dried and evaporated to dryness. Yield 13.0 g, 91% 4- (2,3-dihydro-5-nitro-1 Ninden-2-yl) -1H-imidazole.

Reduction of 4- (2,3-dihydro-5-nitro-1H-inden-2-yl) -1 Nimidazole to 4- (5-amino-2,3-dihydro-1H-inden-2-yl) -1H-imidazole is carried out by adding 1.0 g of 10% palladium on carbon to 11.7 g (0.0512 mol) of 4- (2,3-dihydro-5-nitro-1H-indene). 2-yl) 1H-imidazole in 100 ml of ethanol and the mixture was shaken under a hydrogen atmosphere at room temperature. When the reaction was complete, the catalyst was removed, the filtrate was concentrated to give 9.63 g (94%) of 4- (5-amino-2,3-dihydro-1H-inden-2yl) -1H-imidazole. The product was purified by flash chromatography eluting with methylene chloride-methanol (9.5: 0.5).

A flask containing fluoroboric acid (48% by weight solution in water, 120 ml) and 9.50 g (0.0475 mol) 4- (5-amino-2,3-dihydro-1H-inden-2-yl) -1H -imidazole is placed in an ice and salt bath and cooled to 0 ° C. A solution of 3.30 g (0.0478 mol) of sodium nitrite in 10 ml of water was poured slowly while maintaining the temperature at 0 ° C and then at room temperature for one hour. The reaction mixture was evaporated twice to dryness with toluene. Thermal decomposition is carried out in a flask, which is heated by means of an electrically heated housing. When the formation of white vapor from boron trifluoride ceases, the heating stops. The crude product was dissolved in methanol, the solution filtered and evaporated to dryness. The yield of crude 4- (5-fluoro2,3-dihydro-1H-inden-2-yl) -1H-imidazole was 9.51 g, 99%. The product was purified by flash chromatography (eluent methylene chloride-methanol 9.5: 0.5).

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, other H- 1 and another H-3), 3.68 (1 H, q, ³ JHH 8.3 Hz, H-2), 6.80-6.86 (1 H, t, H-6), 6.83 (1H, s, im-5), 6.92 (1H, dd, ³ Jhf8.9 Hz, ⁴ Jhh 2.4 Hz, H-4), 7.16 (1H, dd, ³ JHH 8, 1 Hz, ⁴ J _HF 5.3 Hz, H-7), 7.59 (1H, s, im-4).

Separation of the enantiomers

O - (-) - tartaric acid (0.44 g, 0.00293 mol) was dissolved in 2.5 ml of water at 60 ° C. At 60 ° C, the racemate 4- (5fluoro-2,3-dihydro-1H-inden-2-yl) -1H-imidazole (I) (1.03 g, 0.00509 mol) was added and 178 μΙ concentrated. hydrochloric acid. The mixture was stirred at 60 ° C until it became a clear solution. The solution was allowed to cool slowly. The precipitate was collected and recrystallized five times from water to give a salt of the (-) - enantiomer with D - (-) tartaric acid, mp 186-187 ° C.

The (-) - enantiomer attachment product with D - (-) tartaric acid was dissolved in water at 60 ° C and ethyl acetate was added. The solution was basified (pH 10) with dilute sodium hydroxide. The ethyl acetate phase was separated and the aqueous phase was separated.

- 10 extracts twice with ethyl acetate. The combined organic phases f were washed with water. The ethyl acetate was evaporated to dryness and the residue was crystallized from ethyl acetate. The product was filtered off by suction and washed with cold ethyl acetate, mp 139 ° C (DSC), specific rotation at 20 ° C in methanol solution -3.7 ° (c = 20 mg / ml).

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

The (+) -enantiomer can be separated in the same way as the (-) - isomer using the 1 - (+) - tartaric acid as a separator to give the 1 - (+) tartaric acid addition salt with (+ ) -enantiomer, mp 187-189 ° C. The base and the hydrogen chloride salt (m.p. 190 ° C) were prepared as described above. The chromatographic purity of the hydrogen chloride salt is 98.7% (HPLC), the optical purity is 99.6% (HPLC), the specific rotation at room temperature in aqueous solution + 3.2 ° (c = 20 mg / ml).

• • · • • · · · • • • · · · · · • · • · • · · · • • · · • · • · · • · · * · · · • · · • · • · · · · · · · • • · • • • · · 1

Claims (6)

1. (-) - Enantiomer of 4- (5-fluoro-2,3-dihydro-1H-inden-2yl) -1H-imidazole and its pharmaceutically acceptable salts. 2. A process for the preparation of 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) - 1 H-imidazole is converted to the diastereoisomeric salt mixture by reaction with an optically active acid, after which the diastereoisomeric salt mixture is separated by fractional crystallization and the separated (-) - enantiomer of 4- (5-fluoro-2,3dihydro-1H- inden-2-yl) -1H-imidazole salt is converted into the free base. A method according to claim 2, characterized in that the optically active acid is O - (-) - tartaric acid. 4. (+) -enantiomer of 4- (5-fluoro-2,3-dihydro-1H-inden-2yl) -1H-imidazole and its pharmaceutically acceptable salts. 5. Method for separating 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) -1 Nimidazole is converted to a diastereoisomeric salt mixture by reaction with an optically active acid, after which the diastereoisomeric salt mixture is separated by fractional crystallization and the separated (+) enantiomer of 4- (5-fluoro-2,3dihydro-1H-indene) -2-yl) -1H-imidazole salt is converted to the free base. A method according to claim 5, characterized in that the optically active acid is N - (+) - tartaric acid.