CS235335B2 - Process for the preparation of tautomeric 5-substituted 4,4a, 5,6,7,8,8a, 9-octahydro-1H (and 2H) -pyrazolo [3,4-g] quinolines - Google Patents

Abstract

A method for the preparation of tautomeric 5-substituted 4s4a,5,6,7,8,8a,9-octahydro-1H(a 2H)pyrazolo(3,4-gl equinalines of the general formulas IIIa" and IIIb* in which R" represents an alkyl group with 1 to 3 carbon atoms, characterized in that the forqjrlderivat of the general formula IVb in which 3" has the above-mentioned meaning. or its tautomer, is allowed to react with hydrazine in an aqueous medium.

Description

The invention describes an improved process for the preparation of tautomeric 5-substituted 4,48,5,6,7,8, 8a,9-octahydro-1H(and 2H)-pyrazolo[3,4-g]quinolines using novel intermediate keto derivatives.

A group of octahydropyrazolo[3,4-g]quinolines is described in U.S. Patent No. 4,198,415, issued April 15, 1980, and in copending U.S. Patent No. 4,230,861, issued October 28, 1980. Both intermediates and final products are described in these publications, and one of the processes for preparing these compounds, described in the above-mentioned publications, can be illustrated by the following reaction scheme:

— -_* ^o— — ^r1 h,cn-chX- ^a -n'' ^{! J} I

R ^C H ₃ I

l L (lile) (Illb)

In the above mentioned schemes

R represents a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, an allyl group or a benzyl group and

R ¹ represents a hydrogen atom or a residue of the formula COOZ', where z' represents an alkyl group with 1 or 2 carbon atoms, a benzyl group, an alpha-methylbenzyl group or a phenylethyl group.

Those compounds of formula IIIa or IIIb, where R ¹ is hydrogen and R is an alkyl group of 1 to 3 carbon atoms or an allyl group, are useful as inhibitors of prolactin secretion and for the treatment of Parkinson's syndrome. Those compounds of formula IIIa or IIIb, where R is hydrogen as well as benzyl or where R ¹ is a residue of the formula COOZ', are useful as intermediates. These intermediates are converted to the corresponding drugs by the processes described in the above-cited patents, the reagent used to convert the 1-substituted 6-oxodecahydroquinone optionally substituted in position 6, of formula I, to the intermediate of formula II, is dimethylformamide acetal, such as dimethylformamide dimethylacetal.

In accordance with the invention, it has now been surprisingly found that novel intermediate keto derivatives provide a better route to the preparation of a certain group of compounds falling within the scope of the above general formulas IIIa and IIIb. The advantages associated with the use of these novel intermediates are the possibility of using cheaper reagents, higher yields of the final products and the fact that the intermediate keto derivative does not have to be isolated (although it can be isolated if desired).

Accordingly, the subject of the invention is a process for the preparation of tautomeric 5-substituted 4,4a,5,6,7,8,8a,9-octahydro-1H(and 2H) pyrazolo[3,4-g]quinolines of general formulas IIIa and IIIb

R' (lila) (Illb) in which

R* represents an alkyl group with 1 to 3 carbon atoms, characterized in that the formyl derivative of the general formula IVb

(IVb) in which

R* having the above meaning, or its tautomer, is allowed to react with hydrazine in an aqueous medium.

The starting formyl derivatives, which can exist in a number of tautomeric forms, can be prepared according to the following reaction scheme I:

Reaction Scheme I (I) r· base alkyl ester of formic acid with 1 to 6 carbon atoms in the alkyl part oTíjúi « xOQ

R (IVa) (IVb) dvc) two)

In accordance with reaction scheme I, trans-dl-1-substituted 6-oxodecahydroquinoline of general formula I is formylated by reaction with an alkyl ester of formic acid containing 1 to 6 carbon atoms in the alkyl moiety in the presence of a base, to form trans-dl-1-aubst.6-oxo-7-formyldecahydroquinoline represented by a series of tautomeric structures (see formulas IVa to IVd). This intermediate is not purposefully isolated (although it is of course possible) and its characterization is not carried out, but is immediately reacted in situ with hydrazine in accordance with the invention to form a mixture of tautomers, i.e. trans-dl-5-substituted 4,4e,5,6,7,8,8a,9-octahydro-1H-pyrazolo[3,4-g]quinoline (IIIa ¹¹ ) and trans-dl-5-substituted 4,4a,5,6,7,8,8a,9-octahydro-2H-pyrazolo[3,4-g]quinoline (IIIb ).

The formylated product described above with four tautomeric structures (formulae IVa to IVd) in aqueous solution probably exists predominantly as the zwitterion represented by formula IVb. However, all of the above tautomeric forms are in dynamic equilibrium and whenever one of these structures is depicted or described herein, it always includes all of the other structures. The invention also includes resonance structures of the various formulae listed above, such as

(IVb)

The procedure according to reaction scheme I is a modification of the Claisaen condensation, in which the methylene group, activated by the presence of an adjacent carbonyl group, can be acylated in the presence of a base. Sodium ethoxide is usually used as the base, although it is obvious that other bases can also be used for this purpose, such as alkali metal tertiary alkoxides and alkali metal hydrides, in particular potassium tertiary butoxide, potassium tertiary amyloxide or sodium hydride.

The Claissen condensation reaction (I->IV) is usually carried out in an ethanol solution, although other lower alkanols and similar polar anhydrous solvents can of course also be used as reaction media. Examples of suitable solvents include tetrahydrofuran, diethyl ether, dimethoxyethane, dioxane, dimethyl sulfoxide, dimethylformamide and tert-butanol, preferably tetrahydrofuran, which can also serve as a solvent for the subsequent cyclization step. Although the temperature of the reaction is not critical, it is nevertheless advantageous to operate at a temperature of about -20°C to reflux, in particular in the range of 0°C to room temperature.

In the cyclization step (IV->IIIa* + IIIb) according to the invention, hydrazine is mentioned as a specific reactant, but hydrazine hydrate or hydrazine salts can also be used with the same result. Suitable solvents for this cyclization step are water, alkanols with 1 to 4 carbon atoms, especially tert-butanol, tetrahydrofuran, dimethylsulfoxide, dimethylethane, dioxane and diethyl ether. The reaction can be carried out at a temperature of about 0 °C to reflux, with room temperature being preferred.

The advantage of the synthetic procedure described above is that both the formylation and the cyclization can be carried out in the same reaction vessel. Thus, solvents suitable for both reactions are preferably used, such as tetrahydrofuran, dimethylsulfoxide, tert-butanol, dimethylether, diethyl ether and dioxane, especially tetrahydrofuran. If desired, water or an alkanol with 1 to 4 carbon atoms can be added to the reaction system. The reaction can be carried out at a pH in the range of about 13 to 0, and preferably at a pH of about 9. A preferred pH of about 9 is achieved by adding a 10X hydrochloric acid solution (1 mol) to the reaction mixture. Although a temperature range of about 0°C to reflux can be used, room temperature is preferred.

A second advantage of the process according to the invention is that the yields of tautomeric pyrazoles (IIIa + IIIb') are higher than those obtained by working with the prior art process using dimethylformamide dimethylacetal as the reagent. Another advantage is that the formylating agent preferably used - ethyl formate - is relatively inexpensive compared to dimethylformamide dimethylacetal.

It should be noted that the numbering of the starting ketone of formula I differs from the numbering of the final pyrazole product of formula III. Thus, the asymmetric carbon connecting the rings adjacent to the quinoline nitrogen in the starting ketone is numbered 8a in the starting ketone, while it is 4a in the pyrazole derivative. The second asymmetric carbon connecting the rings is then numbered 4a in the keto derivative, while it is 8a in the final product. The racemic pairs of formulas IIIa and IIIb are usually referred to as the cis-dl-pair and the trans-dl-pair. The configuration of the molecule at ^4a ^and ^8a ⁱⁿ the j- ^s_ 61-pair will therefore be 4aR,4aS and 4aS,8aR, and in the trans-dl-pair 4aR,8aR and 4aS,8aS. The configurations in the starting materials are of course preserved during the pyrazoloquinoline synthesis, as the Claisen condensation and subsequent cyclization using hydrazine do not affect the configuration at these optical centers.

Our related Czechoslovak patent specification No. 234,050 describes a method for separating trans-dl-1-n-propyl-6-oxodecahydroquinoline corresponding to the general formula I, in which R represents an n-propyl group, into individual stereoisomers of formula la (4aR,8aR) and Ib (4aS, 8aS).

Η I nC ₃ ^H 7 (Ib) . The method described above can be used both in the case of separated isoethers (Ia and Ib) and in the case of the trans-dl-racemate, as shown in reaction scheme 1.

The procedure according to reaction scheme I with subsequent cyclization according to the invention is shown in the following reaction scheme II, where the isomer, i.e. 4aR,8aR-1-n-propyl-6-oxodecahydroquinoline, is used to prepare the desired 4aR,8aR-4>4a,5,6,7,8,8a,9-octahydro-1H(a 2H)pyrazolo[3,4-g]quinoline.

Reaction scheme II

H

O

H hcooc ₂ h _{5 o} base nC ₃ H ₇

H

OH

(IVa (Ia)

N

(lile') <IIIb')

The advantage of the procedure described in reaction scheme II lies in the fact that instead of cyclizing the corresponding trans-dl-racemet and resolving the resulting trans-dl-pyrazoloquinoline, the trans-dl-ketone in formula X is resolved and the pure 4aR,8aR-stereoisomer (Ia) is cyclized to the optically active trans-4hR,8aR-octahydropyrazolo[3,4-g]quinoline. Since at least half of the racemic mixture is lost during the resolution, it is of course much more economical to lose half of the starting material than half of the resulting product, especially considering that organic reactions such as the cyclization of ketoquinoline to pyrazoloquinoline never proceed quantitatively.

The invention is illustrated by the following examples, which do not limit the scope of the invention in any way.

Example 1

In a dry 250 ml round-bottomed flask, 1.5 g of potassium tert-butoxide are weighed and dissolved by adding 25 ml of tetrahydrofuran. To this solution of tert-butoxide is added a solution of 0.8) l of ethyl formate and 0.97 g of trans-dl-1-n-propyl-6-oxodecahydroquinoline in 10 l of tetrahydrofuran, the reaction mixture is allowed to react for about 45 minutes at room temperature, after which 2 l of hydrazine and appropriate amounts of 15% aqueous hydrochloric acid are added to it to reduce the pH to about 9. The resulting mixture is stirred for 30 minutes at room temperature, after which time thin layer chromatography indicates that no starting keto derivative is present. The reaction mixture is poured into 10% aqueous sodium hydroxide and a basic mixture and extracted with an equal volume of methylene dichloride. The extract was dried and the solvent was evaporated in vacuo to give 1.31 g of a pale oil consisting of crude trans-dl-5-n-propyl-4,4a,5,6,7,8,8a,9-octahydro-1H(a 2H)pyrazolo[3,4-g]quinoline.

Example 2

A 25 ml round bottom flask was charged with an appropriate amount of a 55% suspension of sodium hydride in mineral oil containing 360 mg (15 mmol) of sodium hydride and the mineral oil was removed by washing three times with hexane. The remaining sodium hydride was suspended in 6 ml of tetrahydrofuran, to which was added first 740 ml of ethyl formate and 1 drop of anhydrous ethanol, and then 975 mg of trans-dl-1-n-propyl-6-oxodecahydroquinoline in 4 ml of tetrahydrofuran.

The reaction mixture, which began to reflux almost immediately, was heated to reflux for about 45 minutes. After this time, the reaction mixture was free of starting material as determined by thin layer chromatography. After addition of 50 ml of water and 4 ml of hydrazine, the pH was adjusted to about 9 with dilute aqueous hydrochloric acid and the mixture was stirred at room temperature overnight, during which a precipitate separated. Isolation of this precipitate gave 373 mg of trans-dl-5-n-propyl-4,4a,5,6,7,8,8a,9-octahydro-1H(u 2H)pyrazolo[3,4-g]quinolines as a white powder melting at 78-84 °C.

Analysis: for ^c t3 ^H 2l ^N 3 calculated 71.19% C, 9.65% H, 19.16% N;

found 70.89% C, 9.15% H, 19.34% N.

Additional material was obtained by pouring the filtrate into dilute aqueous sodium hydroxide solution and extracting the alkaline solution several times with methylene dichloride. The methylene dichloride extracts were dried and concentrated to give 623 mg of a white foamy material which was purified by chromatography on silica gel using tetrahydrofuran with a trace of ammonium hydroxide as eluent. The initially eluted fractions containing the desired pyrazolo[3,4-g]quinoline were combined and evaporated to give 437 mg of a colorless oil.

This oily material is converted to the dihydrochloride which, after recrystallization from a mixture of methanol and acetone, melts at 252-263°C.

The above experiment is repeated using 125 mg of trans-4aR,8aR-n-propyl-6-oxodecahydroquinoline and the amount of ethyl formate and base (sodium hydride instead of potassium tert-butoxide) is reduced accordingly. After the reaction is practically complete (as indicated by the disappearance of the starting material from the thin layer chromatogram of the reaction mixture sample), the reaction mixture is poured into dilute aqueous sodium hydroxide solution and the basic mixture is extracted with methylene dichloride. After drying the methylene dichloride extract and subsequent evaporation of the solvent in vacuo, approximately 144 mg of a colorless viscous oil is obtained, which gives only one spot on thin layer chromatography. This oily material is dissolved in methanol and 3.2 ml of 0.20N aqueous hydrochloric acid are added to the solution. The resulting yellow solution was concentrated to give a semi-solid yellow substance which was dissolved in methanol. The methanolic solution was decolorized with activated carbon and this was removed by filtration through diatomaceous earth. After evaporation of the solvent and recrystallization of the residue from a mixture of methanol and ethyl acetate, 80 mg of buttery yellow powder 4aR,8aR-5-n-propyl-4,4a,5,6,7, 8,8a,9-octahydro-1H(e 2H)pyrazolo [3,4-g] quinolines with an optical rotation alpha^ ^x -121.76 ° (water, c = 1) were obtained.

Example 3

To a solution of 59.8 g of potassium tert-butoxide in 600 ml of tetrahydrofuran, previously cooled to about 0 °C, is added a solution of 52 g of optically pure 4aR,8aR-1-n-propyl-6-oxodecahydroquinoline and 79 g of ethyl formate in 250 ml of tetrahydrofuran. Gas is released during the addition. The reaction mixture is stirred first for 0.5 hour at a temperature of about 0 °C and then for a further hour at room temperature, after which 25.6 g of hydrazine are added and the pH of the solution is adjusted to about pH 9 by adding about 500 ml of 10% aqueous hydrochloric acid. The resulting mixture is stirred intensively for 2 hours at room temperature, then poured into water and the aqueous mixture is made strongly alkaline (pH about 13) with dilute aqueous sodium hydroxide. The basic mixture was extracted with methylene dichloride, the methylene dichloride extract was dried and the solvent was evaporated. The yellow foamy residue contained, according to thin layer chromatography, the desired pyrazoloquinoline together with a small amount of a single impurity.

235336

This residue is dissolved in 1 liter of hot methanol, to which is added 250 ml of 1H aqueous hydrochloric acid. After concentration of the solution, 65.4 g of 4aH,8aR-5-n-propyl-4,4a,5,6,7,8,8a,9-octahydro-1H(a 2H)pyrazolo[3,4-g]quinoline hydrochloride is obtained as a yellowish solid, which, after recrystallization from a mixture of methanol and ethyl acetate, gives 51.7 g (yield 76%) of a yellowish solid with an optical rotation (α > -121.0 ⁰ water, C 1) and [α] -377.40 (water, C 1).

Analysis:

calculated 61.04 # C, 8.67 * H, 16.43% H, 13.68% Cl;

found 61.32 » C, 8.53% H, 16.22 » N, 14.08% Cl.

Example 4

To a solution of 3.6 g of potassium tert-butoxide in 50 ml of tetrahydrofuran at 0 °C is added a solution of 5.0 g of trans-dl-1-n-propyl-6-oxodecahydroquinoline and 2.36 g of ethyl formate in 25 ml of tetrahydrofuran. The resulting solution is stirred for 15 minutes at 0 °C and then for 17 hours at room temperature, the yellow precipitate formed is filtered off in vacuo and, after washing with tetrahydrofuran, dried in vacuo. The potassium salt of trans-dl-1-n-propyl-6-oxo-7-foryldecahydroquinoline is obtained.

NMR (deuterium oxide, δ values): 9.00 (singlet, IH, CHO), 3.02 - 0.99 (multiplet, 16H),

0.84 (triplet, J » 7, 3H, -CH^ from n-C^H?).

The 7-formyl derivative prepared above can be converted into the corresponding product of the general formula IIIa" or IIIb" by the method described above according to the invention.

The following section presents examples of the resolution of starting materials and products into individual optically active isomers, the preparation of optically active products from the corresponding optically active starting materials, and the results of tests of the pharmacological efficacy of the final compounds.

Example 5 g of trans-(+)-5-n-propyl-4,4a,5,6,7,8,8a,9-octahydro-1H(a 2H)-pyrazolo[3,4-g]quinoline dihydrochloride are dissolved in water and the aqueous solution is made alkaline by adding solid potassium carbonate. The aqueous phase is extracted several times with chloroform to remove the free base, which is insoluble in the alkaline layer and is separated from it. The extracts are combined, dried and the solvent is evaporated in vacuo. 4.7 g of a clear orange oil consisting of trans-(+)-5-n-propyl-4,4a,5,6,7,8,8a,9-octahydro-1H(e 2H)-pyrazolo[3,4-g]equinoline in the form of the free base formed during the neutralization described above are isolated.

1.8 g of this free base are dissolved in methanol and a hot methanolic solution of 1.5 g of (+)-tartaric acid is added to this solution. The reaction solution is heated to boiling for 5 minutes and then allowed to cool to room temperature. A colorless crystalline substance enriched in 4aS,8aS-5-n-propyl-4,4a,5,6,7,8,8a,9-octahydro-1H(a 2H)-pyrazolo[3,4-g]quinoline with (+)-tartaric acid precipitates. The precipitate is filtered off and the filter cake is washed with ether, yielding 1.46 g of solid product. This fraction has an optical rotation [αφσ] (water) +32.76?

and melts at 173-177 °C. This solid material, after recrystallization from hot methanol, gives 0.70 g of a colorless crystalline substance having an optical rotation of alpha & (water) >· +58.44° and melting at 185-186 °C. This solid is recrystallized from hot methanol to give 0.15 g of the pure salt of 4aSpeaS-5-n-propyl-4,4a,5,6,7,8,8e,9-octehydro-1H(a 2H)-pyrazolo[3,4-g]quinoline 8 (+)-tartaric acid as a colorless crystalline product having an optical rotation of [alpha jp? (water) “ +93.88° and a melting point of 201-202 °C. Neither the melting point nor the optical rotation is improved by further recrystallization.

Analysis: calculated for C12H16N10O2 55.27% C, 7.37% H, 11.37% N;

found 55.00% C, 7.13 9 H, 11.19 ÍM,

Example 6

Trans-(+)-1-n-propyl-6-oxadecahydroquinoline is resolved using the procedure described below.

g of (-)-di-p-toluoyltartaric acid is dissolved in 75 ml of warm methanol and this solution is added to a solution of 5.05 g of trans-(+)-1-n-propyl-6-oxodecahydroquinoline in 15 ml of methanol. The reaction mixture is heated to boiling and then allowed to cool to room temperature, at which it is left to stand overnight. Crystallization is induced by seeding with a crystal of the authentic compound, the crystalline tartrate is isolated by filtration and the filter cake is washed with methanol. 2.813 g (18.7 g) of a white crystalline substance consisting of (-)-di-p-toluoyltartrate of 4aR,8aR-1-n-propyl-6-oxodecahydroquinoline with an optical rotation [alpha]^ = -107.49° (methanol, c = 1) are obtained.

The filtrates and mother liquors from the previous process or from analogous processes carried out on a larger scale are combined to obtain a solution of 1-n-propyl-6-oxodecahydroquinoline enriched in the 4aS,8aS-isomer, with a reduced content of the 4aR,8aR-isomer. This solution is treated with (+)-ditoluoyltartaric acid monohydrate as described above to give 4aS,8aS”ln-propyl-6-oxodecahydroquinoline-(+)-ditoluoyltartrate with an optical purity of approximately 80%. 20 g of this salt, after crystallization from 250 ml of methanol, gives 12 g of a white crystalline powder melting with decomposition at 167.5 to 169.5 °C, with an optical rotation of [alpha]j^ _with +106.3° (methanol, c = 1.0); [alpha]jj = +506.7° (methanol, c = 1.0). These data indicate an optical purity of approximately 90 9. The second portion of the product, obtained from the mother liquors from the above-described crystallization, gives 2.3 g of a white solid melting with decomposition at 166.0 to 166.5 °C, with an optical rotation of rotation [alpha]^ = 106.6°; [alpha]^g^ = +510.8° (in both cases methanol, c = 1.0), which indicates an optical purity of about 94 9. After recrystallization of the first and second portions of crystals from methanol, a white solid is obtained, from which the free base is prepared by standard procedures. This free base gives, by distillation, 4.14 g of a colorless oil boiling at 82 to 86 °C/ /17.3 Pa, consisting of 4aS,8aS-1-n-propyl-6-oxodecahydroquinoline with an optical rotation [alpha]^ ⁵ +86.2°; [alpha] ^55 “ +376.6® (in both cases methanol, c = 1.0) with an optical purity of about 98 9.

4.04 g of the free base prepared above is dissolved in .0 ml of methanol, to which is added a solution of 8.35 g of (+)-ditoluoyltartaric acid monohydrate in 65 ml of methanol. The resulting solution is concentrated to a volume of 50 ml, at which time a precipitate begins to separate from it. The reaction mixture is left to stand overnight at room temperature, during which time further crystallization occurs.

After filtering off the crystals, 10.87 g of a white powder melting at 167.0 to 167.5 °C is obtained. This salt is converted to the free base, which distils at 83 to 86 °C/17.3 Pa and has an optical rotation [alpha]| ⁵ = 86.9°; alphaJ^j = 378.8° (in both cases methanol, c * 1.0), which indicates an optical purity of about 98 9.

Alternatively, trans-(+)-1-n-propyl-6-oxodecahydroquinoline can be treated directly with (+)-di-p-toluoyl tartrate to give 4aS,8aS-1-n-propyl-6-oxodecahydroquinoline-(+)-di-p-toluoyl tartrate, which is purified as described above for the salt of the 4aR,8aR isomer.

Example 7

4eS,8aS-1-n-propyl-6-oxodecahydroquinoline, prepared by the above procedure, is converted into 4aS,8aS-5-n-propyl-3,4,4e,5,6,7,8,8a,9-octahydro-1H(e 2H)-pyresolo[4,3-g]quinoline in the following manner.

7.7 g of potassium tert-butoxide are dissolved in 85 ml of tetrahydrofuran, the resulting solution is cooled to about 0 °C and a mixture of 6.7 g of 4aS,8aS-1-n-propyl-6-oxodecahydroquinoline and 10.2 g of ethyl formate in 40 ml of tetrahydrofuran is added. Gas is evolved during the addition. The reaction mixture is allowed to warm to room temperature and a sample is subjected to thin layer chromatography, which shows that no starting material is present. 6 ml of hydrazine hydrate are added and the pH is then adjusted to about 9 with 10% hydrochloric acid. The mixture is stirred vigorously at room temperature until no intermediate formyl ketone is present according to thin layer chromatography. The reaction mixture is poured into dilute aqueous sodium hydroxide solution and the basic mixture is extracted with methylene dichloride. The methylene dichloride extract was dried and the solvent evaporated in vacuo to give 9 g of a colorless powder. This powder was dissolved in 100 mL of methanol to which was added an equivalent amount of 1M aqueous hydrochloric acid. The resulting solution was concentrated to give a white solid which, upon recrystallization from methanol/ethyl acetate, gave 5.69 g of 4aS,8aS-5-n-propyl-4,4a,5,6,7,8,8a,9-octahydro-1H(a 2H)-pyrazolo(3,4-g)quinoline hydrochloride.

The compounds described in the above examples exhibit their activity as D-1 dopamine agonists in various ways. For example, 4aS,8aS-5-n-propyl-4,4a,5,6,7,8,8a,9-octahydro-1H(a2H)-pyrazolo(4,3-g)quinoline stimulates the formation of cyclic adenosine monophosphate in the striatal membrane of the rat.

This activity is determined by the procedure described by Wong and Reid in Communications in Psychopharmacology, 1, 269 (1980). 4aS,8aS-5-*n-propyl-4,4a,5,6,7,8,8a,9-*octahydro-1H(a 2H)-pyrazolo(4,3-g)quinoline, the corresponding 4aR,8aB-enantiomer and the corresponding racemate are tested for their ability to activate adenylate cyclase in the striatal membrane of rats, which activation is measured as an increase in the concentration of cyclic adenosine monophosphate. The results of this assay are shown in Table 1. Dopaine is used as a positive control. The first column of Table 1 lists the test substance, the second column the concentration of the test substance and the third column the production of cyclic adenosine monophosphate as a percentage of the control.

T a b l e 1 k a 1

Test substance Concentration (juaol) Cyclic adenosine monophosphate production in % compared to control Dopamine . 10 50 100 149.7 + 7.2 215.5 + 28.8 183.8 + 12.5 ^κ) Racemate 50 116.5 + 13.3 4aB,8aR-enantiomer 50 114.2 + 10.4 4aS,SaS-enantiomer 50 141.8 + 9.3 »’

In the presence of 10 μmol guanosine triphosphate, the basal value of adenylate cyclase activity in rat striatal membranes (+ standard deviation) is 134.9 ± 6.1 pmol/min/mg protein. Compounds are tested in three or more separate experiments. Significant (p < 0.025) production of cyclic adenosine monophosphate is indicated by an asterisk (x).

According to the data presented in Table 1, only the 4aS,8aS-enantiomer significantly increases the production of cyclic adenosine monophosphate, which was indicative of the efficacy of a D-1 dopamine agonist.

A second, particularly sensitive indicator of D-1 agonist activity is the release of cyclic adenosine monophosphate from tissue sections using the procedure described by Stoof and Kebabian (ibid.). In this procedure, striatal tissue is separated from the rat brain and cut into fragments measuring 0.3 mm x 0.03 mm. The tissue fragments are suspended in a suitable buffer system (e.g., Earle's balanced salt solution) and a gas stream consisting of 95 parts oxygen and 5 parts carbon dioxide is continuously introduced into the suspension while maintaining the temperature at 37°C. Immediately before use, the tissue fragments are transferred to fresh medium to which bovine serum albumin (2.5 mg/ml) and 3-isobutyl-1-methylxanthine (1 mmol) are added to prevent the breakdown of cyclic adenosine monophosphate. The tissue fragments are incubated in buffer without the addition of the test substances and then transferred to the same medium to which the test compound has been added. Samples of the incubation media (without addition and with addition of the test substance) are examined for the concentration of cyclic adenosine monophosphate using a specific radioimmunological procedure. The effect of the test substance or substances on the release of cyclic adenosine monophosphate is expressed as a percentage relative to the control.

The test is performed using the following environment:

Folder Concentration (mg/liter) sodium chloride 4,800 potassium chloride 402.6 sodium bicarbonate 2,201.1 sodium dihydrogen phosphate 137.99 magnesium sulfate heptahydrate 147.88 d-glucose 1,009 calcium chloride dihydrate 191.1 phenol red ¹⁰

In the experiments described above, Stoof and Kebabian use sulpiride to suppress the negative (anti D-1) effect of all substances acting as D-2 dopamine agonists.

The authors mentioned demonstrated that a D-2 agonist suppresses the production of cyclic adenosine monophosphate (an effect opposite to that produced by a D-1 agonist). Sulpiride is known to be an antagonist of the D-2 receptors of the pituitary gland. The addition of sulpiride to an experimental system, such as that used in the above test, blocks all D-2 effects of the test substance in terms of reducing the production of cyclic adenosine monophosphate. Stoof and Kebabian demonstrated the loss of the effect of sulpiride on the production of cyclic adenosine monophosphate in rat striatal tissue using SKF 38393 as a pure D-1 agonist, which indicates that D-2 receptors are not involved and that the compound is not effective as a D-2 agonist.

The results of one such assay using 4aS,8aS-5-n-propyl-4,4a,5,6,7,8,8a,9-octahydro-1H(a 2H)-pyrazolo[3,4-g]quinoline dihydrochloride (Compound A) are given in Table 2. Column 1 of this table lists the compound added (if any), column 2 the concentration of that compound, column 3 the concentration of cyclic adenosine monophosphate present, and column 4 the percentage increase in cyclic adenosine monophosphate concentration.

Table 2

Test substance Concentration Cyclic adenosine monophosphate acid concentration Increase XX) concentration of cyclic adenosine monophosphate 71.6 + 8.2 0 A 5 x 10 ⁷ l 131.0 + 9.2 83 A 5 x 10 ⁶ l 160.1 + 23.8 124 A + sulpiride (10 ⁶ li) 5 x 10' ⁷ íí 143.7 + 6.2 100

The above table shows that sulpiride has no effect on increasing the excretion of cyclic adenosine monophosphate.

In the above-mentioned work, Stoof and Kebabian found that the racemate, i.e. trans-(+)-5-n-propyl-4,4a,5,6,7,8,8a,9-octehydro-1H(a 2H)-pyrazolo-[4,3-g]quinoline (LY141865), reduces the concentration of cyclic adenosine monophosphate (see p. 367, graph G of the above-mentioned authors' work). The addition of sulpiride has little or no effect, and at best returns the concentration of cyclic adenosine monophosphate to the control level. The same racemic compound reduces the effect of SKP38393, consisting in increasing the level of cyclic adenosine monophosphate by 57 ± 8% (see figure 3 on p. 368 of the above-mentioned authors' work). The addition of sulpiride suppresses this effect, and the levels of cyclic adenosine monophosphate are essentially the same as in the case of using SKP38393 alone.

The data presented by Stoof and Kebabian are essentially consistent with the conclusion that the 4aR,8aR-enantiomer, which is a known D-2 agonist, is the active component of the racemate (LY141865) in reducing cyclic adenosine monophosphate production, an effect that is again suppressed by sulpiride. The trans-(+)-enantiomer does not show activity as a D-2 agonist in the D-2 agonist potency assay.

In a separate but similar experiment, it was confirmed that SKF38393 increases the production of cyclic adenosine monophosphate (145 X at a concentration of 10“ ⁶ 1I). This effect is reduced by the addition of 4aR,8aR-5-n-propyl-4,4a,5,6,7,8,8a,9-octahydro-1H(a 2H)-pyrazolo[4,3-g]quinoline, trans-(-)-enantiomer and D-2 agonist at a dose of 0.5 x 10~®mol (from 145% to 42 X). This effect is suppressed by the addition of sulpiride (10“®M) to the system.

Claims (3)

OF THE INVENTION A process for the preparation of the 5-substituted 4,40,5,6,7,8,8a, 9-octahydro-1H (and 2H) pyrazolo [3,4-g] quinolines of the general formulas IIIa and IIIb (IIIa) (IIIb) ) in which R represents a C 1 -C 3 alkyl group, characterized in that the formyl derivative of the general formula IVb R in which R is as defined above, or a tautomer thereof, reacted with hydrazine in an aqueous medium. 2. Method according to claim 1, characterized in that a starting material is used. a ketoderivative of formula (IVb) in the 4aR, 8aR configuration. 3. The method of claim 1, wherein the starting ketoderivative of formula (IVb) is in the 4aS, 8aS configuration.