Abstract:
The invention relates to 2,5-dihydropyrazolo[ 3,4 -d]pyrimidin-4-ones and their tautomers which contain in the 5-position an ar(alkyl) radical and in the 2-position a hydrogen or an ar(alkyl) radical, processes for their preparation and their use as medicaments, in particular for the treatment of epilepsy of various forms.

Description:
TECHNICAL FIELD  
         [0001]    The invention relates to 2,5-dihydropyrazolo-[3,4-d]pyrimidin-4-ones and their tautomers which contain an ar(alkyl) radical in the 5-position and a hydrogen or an ar(alkyl) radical in the 2-position, processes for their preparation and their use as medicaments, in particular for the treatment of epilepsy of various forms. On account of the structural similarities to adenine, pyrazolo[3,4-d]pyrimidines are compounds of pharmacological interest.  
         PRIOR ART  
         [0002]    Hitherto, only 5-benzyl-2,5-dihydropyrazolo[3,4-d]pyrimidin-4-one and 5-phenethyl-2,5-dihydropyrazolo[3,4-d]pyrimidin-4-one have been described [Sochneva, E. O.; Solov&#39;eva, N. P.; Granik, V. G., Khim. Geterotsikl. Soedin. 1978, (12), 1671-6; Granik, V. G.; Sochneva, E. O.; Solov&#39;eva, N. P.; Shvarts, G. Ya.; Syubaev, R. D.; Mashkovskii, M. D., Khim.-Farm. Zh. 1980, 14(6), 36-40]. These compounds were investigated for antiinflammatory action; an anticonvulsant action is not mentioned or suggested.  
           [0003]    5-Arylmetyl-2,5-dihydropyrazolo[3,4-d]pyrimidin-4-ones [sic] which have a further substituent in the pyrazole ring are not known.  
           [0004]    Known anticonvulsants on the one hand have the disadvantage that undesired side effects, such as neurotoxicity and idiosyncrasies, occur and on the other hand these are not active in certain forms of epilepsy.  
           [0005]    The invention is therefore based on the object of making available, compounds having favorable pharmacological properties which have anticonvulsant activity and can be employed as medicaments, in particular for the treatment of epilepsy. 
       
    
    
     DESCRIPTION OF THE INVENTION  
       [0006]    According to the present invention, these novel compounds are 2,5-dihydropyrazolo[3,4-d]pyrimidin-4-ones of the general formula 1  
                         
 
         [0007]    or their tautomers, where  
         [0008]    R=CH 2 -phenyl, in which phenyl can be mono- or polysubstituted by halogen, C 1 -C 3 -alkyl, straight-chain or branched, optionally mono- or polysubstituted by halogen C 1 -C 3 -alkyloxy, straight-chain or branched phenyl NO 2  CN; CH 2 -pyridinyl  
         [0009]    R 1 =H; C 1 -C 4 -alkyl; phenyl; CH 2 -phenyl, in which phenyl can optionally be substituted by halogen; CH 2 -pyridinyl; tetrahydrofuranylmethyl  
         [0010]    R 2 =H, methyl excluding the compound in which R is CH 2 -phenyl and R 1  is hydrogen.  
         [0011]    Examples of compounds of the general formula 1 which may be mentioned are:  
         [0012]    5-(2-chlorobenzyl)-2,5-dihydropyrazolo[3,4-d]pyrimidin-4-one  
         [0013]    5-(4-chlorobenzyl)-2,5-dihydropyrazolo[3,4-d]pyrimidin-4-one  
         [0014]    5-(4-fluorobenzyl)-2,5-dihydropyrazolo[3,4-d]pyrimidin-4-one  
         [0015]    5-(2,4-dichlorobenzyl)-2,5-dihydropyrazolo[3,4-d]-pyrimidin-4-one  
         [0016]    5-(2,6-difluorobenzyl)-2,5-dihydropyrazolo[3,4-d]-pyrimidin-4-one  
         [0017]    5-(2-methylbenzyl)-2,5-dihydropyrazolo[3,4-d]pyrimidin-4-one  
         [0018]    5-(2-methoxybenzyl)-2,5-dihydropyrazolo[3,4-d]-pyrimidin-4-one  
         [0019]    5-(2-trifluoromethylbenzyl)-2,5-dihydropyrazolo[3,4-d]-pyrimidin-4-one  
         [0020]    5-(2,4,6-trimethylbenzyl)-2,5-dihydropyrazolo[3,4-d]-pyrimidin-4-one  
         [0021]    5-(2-pyridinylmethyl)-2,5-dihydropyrazolo[3,4-d]-pyrimidin-4-one  
         [0022]    5-(3-pyridinylmethyl)-2,5-dihydropyrazolo[3,4-d]-pyrimidin-4-one  
         [0023]    5-(4-pyridinylmethyl)-2,5-dihydropyrazolo[3,4-d]-pyrimidin-4-one  
         [0024]    5-benzyl-2-methyl-2,5-dihydropyrazolo[3,4-d]pyrimidin-4-one  
         [0025]    5-(2-methylbenzyl)-2-methyl-2,5-dihydropyrazolo[3,4-d]-pyrimidin-4-one  
         [0026]    5-(3-methylbenzyl)-2-methyl-2,5-dihydropyrazolo[3,4-d]-pyrimidin-4-one  
         [0027]    5-(4-methylbenzyl)-2-methyl-2,5-dihydropyrazolo[3,4-d]-pyrimidin-4-one  
         [0028]    5-(2-methoxybenzyl)-2-methyl-2,5-dihydropyrazolo[3,4-d]-pyrimidin-4-one  
         [0029]    5-(2-chlorobenzyl)-2-methyl-2,5-dihydropyrazolo[3,4-d]-pyrimidin-4-one  
         [0030]    5- (3-chlorobenzyl) -2-methyl-2, 5-dihydropyrazolo[3, 4-d]-pyrimidin-4-one  
         [0031]    5-(2-trifluoromethylbenzyl)-2-methyl-2,5-dihydropyrazolo[3,4-d]pyrimidin-4-one  
         [0032]    5-(2,6-difluorobenzyl)-2-methyl-2,5-dihydropyrazolo[3,4-d]pyrimidin-4-one  
         [0033]    5-(4-trifluoromethylbenzyl)-2-methyl-2,5-dihydropyrazolo[3,4-d]pyrimidin-4-one  
         [0034]    5-(2-chloro-6-fluorobenzyl)-2-methyl-2,5-dihydropyrazolo[3,4-d]pyrimidin-4-one  
         [0035]    5-(2-phenylbenzyl)-2-methyl-2,5-dihydropyrazolo[3,4-d]-pyrimidin-4-one  
         [0036]    5-(2,6-dichlorobenzyl)-2-methyl-2,5-dihydro-pyrazolo[3,4-d]pyrimidin-4-one  
         [0037]    5-(2-nitrobenzyl)-2-methyl-2,5-dihydropyrazolo[3,4-d]-pyrimidin-4-one  
         [0038]    5-(4-chlorobenzyl)-2-methyl-2,5-dihydropyrazolo[3,4-d]-pyrimidin-4-one  
         [0039]    5-(2,4-dichlorobenzyl)-2-methyl-2,5-dihydropyrazolo[3,4-d]pyrimidin-4-one  
         [0040]    5-(2-iodobenzyl)-2-methyl-2,5-dihydropyrazolo[3,4-d]-pyrimidin-4-one  
         [0041]    5-(2-cyanobenzyl)-2-methyl-2,5-dihydropyrazolo[3,4-d]-pyrimidin-4-one  
         [0042]    5-(4-fluorobenzyl)-2-methyl-2,5-dihydropyrazolo[3,4-d]-pyrimidin-4-one  
         [0043]    5-(2,4,6-trimethylbenzyl)-2-methyl-2,5-dihydropyrazolo[3,4-d]pyrimidin-4-one  
         [0044]    5-(2-pyridinylmethyl)-2-methyl-2,5-dihydropyrazolo[3,4-d]-pyrimidin-4-one  
         [0045]    5-(4-pyridinylmethyl)-2-methyl-2,5-dihydropyrazolo[3, 4-d]-pyrimidin-4-one  
         [0046]    5-(2-chloro-6-fluorobenzyl)-2-ethyl-2,5-dihydropyrazolo[3,4-d]pyrimidin-4-one  
         [0047]    5-(4-methylbenzyl)-2-ethyl-2,5-dihydropyrazolo[3,4-d]-pyrimidin-4-one  
         [0048]    5-(2,6-difluorobenzyl)-2-ethyl-2,5-dihydropyrazolo[3,4-d]-pyrimidin-4-one  
         [0049]    5-(2-pyridinylmethyl)-2-ethyl-2,5-dihydropyrazolo[3,4-d]-pyrimidin-4-one  
         [0050]    5-(2-chloro-6-fluorobenzyl)-2-propyl-2,5-dihydropyrazolo[3,4-d]pyrimidin-4-one  
         [0051]    5-(4-methylbenzyl)-2-propyl-2,5-dihydropyrazolo[3,4-d]-pyrimidin-4-one  
         [0052]    5-(2,6-difluorobenzyl)-2-propyl-2,5-dihydropyrazolo[3,4-d]pyrimidin-4-one  
         [0053]    5-(2-pyridinylmethyl)-2-propyl-2,5-dihydropyrazolo[3,4-d]-pyrimidin-4-one  
         [0054]    5-(2-chloro-6-fluorobenzyl)-2-isopropyl-2,5-dihydropyrazolo[3,4-d]pyrimidin-4-one  
         [0055]    5-(4-methylbenzyl)-2-isopropyl-2,5-dihydropyrazolo[3,4-d]-pyrimidin-4-one  
         [0056]    5-(2,6-difluorobenzyl)-2-isopropyl-2,5-dihydropyrazolo[3,4-d]pyrimidin-4-one  
         [0057]    5-(2-pyridinylmethyl)-2-isopropyl-2,5-dihydropyrazolo[3,4-d]pyrimidin-4-one  
         [0058]    5-(2-chloro-6-fluorobenzyl)-2-butyl-2,5-dihydropyrazolo[3,4-d]pyrimidin-4-one  
         [0059]    5-(4-methylbenzyl)-2-butyl-2,5-dihydropyrazolo[3,4-d]-pyrimidin-4-one  
         [0060]    5-(2,6-difluorobenzyl)-2-butyl-2,5-dihydropyrazolo[3,4-d]-pyrimidin-4-one  
         [0061]    5-(2-chloro-6-fluorobenzyl)-2-phenyl-2,5-dihydropyrazolo[3,4-d]pyrimidin-4-one  
         [0062]    5-(4-methylbenzyl)-2-phenyl-2,5-dihydropyrazolo[3,4-d]-pyrimidin-4-one  
         [0063]    5-(2,6-difluorobenzyl)-2-phenyl-2,5-dihydropyrazolo[3,4-d]pyrimidin-4-one  
         [0064]    5-(2-pyridinylmethyl)-2-phenyl-2,5-dihydropyrazolo[3,4-d]-pyrimidin-4-one  
         [0065]    5-(2-chloro-6-fluorobenzyl)-2-benzyl-2,5-dihydropyrazolo[3,4-d]pyrimidin-4-one  
         [0066]    5-(4-methylbenzyl)-2-benzyl-2,5-dihydropyrazolo[3,4-d]-pyrimidin-4-one  
         [0067]    5-(2,6-difluorobenzyl)-2-benzyl-2,5-dihydropyrazolo[3,4-d]pyrimidin-4-one  
         [0068]    5-(2-pyridinylmethyl)-2-benzyl-2,5-dihydropyrazolo[3,4-d]-pyrimidin-4-one  
         [0069]    2,5-bis(2-chlorobenzyl)-2,5-dihydropyrazolo[3,4-d]-pyrimidin-4-one  
         [0070]    5-(2,6-difluorobenzyl)-2-pyridin-2-ylmethyl-2,5-dihydropyrazolo[3,4-d]pyrimidin-4-one  
         [0071]    5-(2-chlorobenzyl)-2-tetrahydrofuran-2-ylmethyl-2,5-dihydropyrazolo[3,4-d]pyrimidin-4-one  
         [0072]    5-(2-chlorobenzyl)-6-methyl-2,5-dihydropyrazolo[3,4-d]-pyrimidin-4-one  
         [0073]    5-(2,6-difluorobenzyl)-6-methyl-2,5-dihydropyrazolo[3,4-d]hpyrimidin-4-one  
         [0074]    5-(2-trifluoromethylbenzyl)-2,6-dimethyl-2,5-dihydropyrazolo[3,4-d]pyrimidin-4-one  
         [0075]    5-(2,6-difluorobenzyl)-2,6-dimethyl-2,5-dihydropyrazolo[3,4-d]pyrimidin-4-one  
         [0076]    The process for the preparation of compounds of the formula 1 and their tautomers starts from known 3-aminopyrazol-4-carboxylic acid esters (compounds of the general formula 2) or 3-aminopyrazole-4-carboxamides (compounds of the general formula 3) [P. Schmidt, J. Druey,  Helv. Chim. Acta.  1956, 39, 986-991; K. Eichenberger, P. Schmidt, M. Wilhelm, J. Druey;  Helv. Chim. Acta  1959, 42, 349-359; J. K. Chakrabarti, T. M. Hotten, I. A. Pullar, N. C. Nicholas,  J. Med. Chem.  1989, 32(12), 2573-2582],  
                         
 
         [0077]    where  
         [0078]    R 1 =H, C 1 -C 4 -alkyl; phenyl; CH 2 -phenyl, in which phenyl can optionally be substituted by halogen; CH 2 -pyridinyl, tetrahydrofuranylmethyl and Et is an alkyl radical.  
         [0079]    These compounds of the general formula 2 or general formula 3 are on the one hand cyclized using formamide (R 2 =H) or acetamide (R 2 =methyl) at relatively high temperatures, alternatively compounds of the general formula 3 are cyclized using orthoformic acid esters and/or formic acid/acetic anhydride mixtures (R 2 =H) or using orthoacetic acid ester and/or acetic anhydride (R 2 =methyl), and then reacted with R-halides, where R has the meaning mentioned, to give compounds of the general formula 1 (Method B).  
         [0080]    On the other hand, compounds of the general formula 3 are reacted with dimethylformamide dimethyl acetal (R 2 =H) or dimethylacetamide dimethyl acetal (R 2 =methyl) and the products thus obtained are reacted with R-amines, where R has the meaning mentioned, to give compounds of the general formula 1 (Method A).  
         [0081]    The compounds according to the invention, just like the already described compound 5-benzyl-2,5-dihydropyrazolo[3,4-d]pyrimidin-4-one, or their pharmaceutically utilizable salts are suitable for the production of pharmaceutical compositions. The pharmaceutical compositions or medicaments can contain one or more of the compounds according to the invention. The customary pharmaceutical vehicles and excipients can be used for the production of the pharmaceutical preparations. The medicaments can be administered, for example, parenterally (e.g. intravenously, intramuscularly, subcutaneously) or orally.  
         [0082]    The administration forms can be prepared by the processes which are generally known and customary in pharmaceutical practice.  
         [0083]    The compounds according to the invention have strong anticonvulsant actions, just like the already described compound 5-benzyl-2,5-dihydropyrazolo[3,4-d]pyrimidin-4-one.  
         [0084]    Anticonvulsant Activity  
         [0085]    The compounds according to the invention were tested for their anticonvulsant action in vivo after i.p. administration to mice according to the international customary standard (Pharmac. Weekblad, Sc. Ed. 14, 132 (1992) and Antiepileptic Drugs, Third Ed., Raven Press, New York 1989) (Table 1).  
                                                                             TABLE 1                           Anticonvulsant action of selected 2,5-       dihydropyrazolo[3, 4-d]pyrimidin-4-ones            Compound 1)     log p 2)     Test 3)     dose 4)     Action 5)                      1   1.14   MES   30   100               PTZ   100   80       2   1.34   MES   100   33               PTZ   100   —       3   0.62   MES   100   33               PTZ   300   60       4   1.96   MES   100   100               PTZ   300   40       5   0.28   MES   30   100               PTZ   300   —       6   1.36   MES   100   67               PTZ   300   100       8   0.78   MES   100   67               PTZ   100   20       13   0.72   MES   100   100               PTZ   300   —       14   1.76   MES   30   100               PTZ   100   80       17   0.92   MES   100   100               PTZ   300   100       19   1.56   MES   100   100               PTZ   300   —       21   0.67   MES   30   100               PTZ   100   80       37   1.43   MES   100   80               PTZ   300   20       43   1.88   MES   300   100               PTZ   300   33       58   2.59   MES   300   —               PTZ   300   —       60   1.67   MES   100   67               PTZ   300   —       5-Benzyl-2,5-   0.47   MES   30   100       dihydropyrazolo[3,4-       PTZ   30   100       d]pyrimidin-4-one       Comparison Substances            Carbamazepine   MES   100   100           PTZ   100   0       Valproate   MES   100   0           PTZ   100   30                                                                  
 
         [0086]    Analogous results were obtained for the oral action.  
         [0087]    For example, for compound 1, (5-(2-chlorobenzyl)-2,5-dihydropyrazolo[3,4-d]pyrimidin-4-one), in the rat in maximal electroshock the ED 50  (p.o.) was determined to be 18 mg/kg and for the neurotoxicity the NT 50  to be &gt;500 mg/kg. This compound is also active in convulsion models using bicuculline and picrotoxin as convulsion-inducing cause. Compound 14 (5-(2-methylbenzyl)-2-methyl-2,5-dihydropyrazolo[3,4-d]pyrimidin-4-one) is likewise strongly anticonvulsant with a large therapeutic breadth (ED 50  (rat p.o.) =9 mg/kg, NT 50 &gt;300 mg/kg). Compound 21 has a similar pharmacological profile (ED 50  (rat p.o.) =3 mg/kg, NT 50 &gt;300 mg/kg).  
         [0088]    Working Examples  
         [0089]    The following examples serve to illustrate the invention further without restricting it to these.  
         [0090]    General Procedure for the Preparation of the Compounds of the Formula 1 and their Tautomers as in Table 2 (Method A)  
         [0091]    50 mmol of 3-aminopyrazole-4-carboxamide are reacted with dimethylformamidedimethyl acetal (R 2 =H) or dimethylacetamide dimethyl acetal (R 2 =methyl) at relatively high temperature, preferably 90-130° C., in/or without an organic solvent. After 12-40 h, excess solvent and reagent is [sic] completely removed. 50 mmol of an R-amine, in which R has the meaning mentioned, are added to the residue and, if appropriate, an inert organic solvent, preferably xylene, chlorobenzene etc. The reaction mixture is reacted at relatively high temperature, preferably 100-180° C. After 10-35 h, the solvent is removed and the compound of the formula 1 is obtained pure by recrystallization from an organic solvent, preferably DMF, ethanol, methanol or acetone, or alternatively by chromatography.  
         [0092]    General Procedure for the Preparation of the Compounds of the Formula 1 and their Tautomers as in Table 2 (Method B)  
         [0093]    1 st  stage  
         [0094]    50 mmol of 3-aminopyrazole-4-carboxylic acid ester/amide are reacted at relatively high temperatures (100-200° C.) for 3-15 hours in formamide (R 2 =H) or acetamide (R 2 =methyl). After completion of the reaction, the products (pyrazolopyrimidines) are either isolated by filtration, or recovered by chromatography after the removal of the solvent.  
         [0095]    Alternatively, 50 mmol of 3-aminopyrazole-4-carboxamide are reacted with orthoformic acid ester and/or with formic acid/acetic anhydride mixture (R 2 =H) or with orthoacetic acid esters and/or with acetic anhydride (R 2 =methyl) for 10-50 h at relatively high temperature, preferably 80-120° C. After completion of the reaction, the products (pyrazolopyrimidines) are either isolated by filtration, or recovered by chromatography after the removal of the solvent.  
         [0096]    2 nd  stage  
         [0097]    20 mol of pyrazolopyrimidine are dissolved in DMF, treated with an inorganic base, preferably sodium, potassium or calcium carbonate, and sodium/potassium iodide and reacted with 25-40 mmol of an R-halide, where R has the meaning mentioned, at relatively high temperature, preferably 50-140° C. After 5-40 h, the reaction mixture is filtered and the compound of the formula 1 is either isolated by filtration, or recovered by chromatography after the removal of the solvent. The crude products thus obtained are recrystallized from an organic solvent, preferably DMF, ethanol, methanol or acetone. Alternatively, purification can be carried out by chromatography.  
                                                                           TABLE 2                           Pyrazolo[3,4-d]pyrimidines                            Yield   M.p.           Compound   R  1)     R 1 1)     R 2 1)     in (%)   (° C.)   Method                    1   2-Cl-Bn   H   H   38   186-187   A       2   4-Cl-Bn   H   H   41   246-247   A       3   4-F-Bn   H   H   84   260-261   A       4   2,4-Cl 2 -Bn   H   H   63   236-237   A       5   2,6-F 2 -Bn   H   H   15   214-216   A       6   2-Me-Bn   H   H   46   221-222   A       7   2-MeO-Bn   H   H   18   188-189   A       8   2-CF 3 -Bn   H   H   29   168-171   A       9   2,4,6-Me 3 -Bn   H   H   34   199-200   A       10   2-Py-CH 2 —   H   H   45   224-225   A       11   3-Py-CH 2 —   H   H   39   200-201   A       12   4-Py-CH 2 —   H   H   47   220-221   A       13   Bn   Me   H   28   202-204   B       14   2-Me-Bn   Me   H   28   185-186   A       15   3-Me-Bn   Me   H   5   114-117   A       16   4-Me-Bn   Me   H   34   224-226   A       17   2-MeO-Bn   Me   H   31   160-162   B       18   2-Cl-Bn   Me   H   25   205-206   A       19   3-Cl-Bn   Me   H   15   169-170   A       20   2-CF 3 -Bn   Me   H   23   215-217   A       21   2,6-F 2 -Bn   Me   H   13   226-228   A       22   4-CF 3 -Bn   Me   H   56   211-212   B       23   2-Cl-6-F-Bn   Me   H   49   216-218   B       24   2-Ph-Bn   Me   H   59   189-191   B       25   2,6-Cl 2 -Bn   Me   H   51   200-202   B       26   2-NO 2 -Bn   Me   H   24   220-222   B       27   4-Cl-Bn   Me   H   62   209-210   B       28   2,4-Cl 2 -Bn   Me   H   60   218-219   B       29   2-1-Bn   Me   H   16   187-190   B       30   2-CN-Bn   Me   H   21   198-199   B       31   4-F-Bn   Me   H   62   216-217   B       32   2,4,6-Me 3 -Bn   Me   H   45   182-184   B       33   2-Py-CH 2 —   Me   H   53   203-205   B       34   4-Py-CH 2 —   Me   H   48   192-195   B       35   2-Cl-6-F-Bn   Et   H   61   207-209   B       36   4-Me-Bn   Et   H   57   178-179   B       37   2,6-F 2 -Bn   Et   H   63   185-187   B       38   2-Py-CH 2 —   Et   H   71   190-191   B       39   2-Cl-6-F-Bn   Pro   H   73   163-165   B       40   4-Me-Bn   Pro   H   68   157-158   B       41   2,6-F 2 -Bn   Pro   H   65   167-168   B       42   2-Py-CH 2 —   Pro   H   72   179-181   B       43   2-Cl-6-F-Bn   i-Pro   H   66   159-161   B       44   4-Me-Bn   i-Pro   H   78   145-147   B       45   2,6-F 2 -Bn   i-Pro   H   74   156-157   B       46   2-Py-CH 2 —   i-Pro   H   63   163-164   B       47   2-Cl-6-F-Bn   Bu   H   45   156-157   B       48   4-Me-Bn   Bu   H   51   146-147   B       49   2,6-F 2 -Bn   Bu   H   62   151-152   B       50   2-Cl-6-F-Bn   Ph   H   67   195-197   B       51   4-Me-Bn   Ph   H   71   182-183   B       52   2,6-F 2 -Bn   Ph   H   65   189-191   B       53   2-Py-CH 2 —   Ph   H   75   199-201   B       54   2-Cl-6-F-Bn   Bn   H   48   176-177   B       55   4-Me-Bn   Bn   H   54   167-169   B       56   2,6-F 2 -Bn   Bn   H   58   173-174   B       57   2-Py-CH 2 —   Bn   H   44   182-184   B       58   2-Cl-Bn   2-Cl-Bn   H   42   167-168   B       59   2,6-F 2 -Bn   2-Py-CH 2 —   H   49   174-175   B       60   2-Cl-Bn   2-THF—CH 2 —   H   39   128-130   A       61   2-Cl-Bn   H   Me   24   222-224   A       62   2,6-F 2 -Bn   H   Me   18   235-236   A       63   2-CF 3 -Bn   Me   Me   47   192-193   B       64   2,6-F 2 -Bn   Me   Me   54   201-202   B