in the definitions of y 1 , y 2 , y 3 , z 1 , z 2 and z 3 in the formula ( i ), the lower alkyl groups are straight - chain or branched alkyl groups having 1 to 4 carbon atoms , for example , methyl , ethyl , n - propyl , i - propyl , n - butyl , i - butyl , etc . in the definitions of y 1 , y 2 , y 3 , z 1 , z 2 and z 3 , the halogen atoms include chlorine , bromine , etc . in the definitions of y 1 , y 2 and y 3 , the lower alkoxycarbonyl groups are straight - chain or branched alkoxycarbonyl groups having 2 to 7 carbon atoms , for example , methoxycarbonyl , ethoxycarbonyl , etc . in the definition of a and b , the naphthyl group includes both α - naphthyl and β - naphthyl , and the lower alkyl group is a straight - chain or branched alkyl group having 1 to 6 carbon atoms , for example , methyl , ethyl , n - propyl , i - propyl , n - butyl , i - butyl , n - pentyl , n - hexyl , etc . in the definition of a and b , the lower alkenyl group is a straight - chain or branched alkenyl group having 1 to 6 carbon atoms , for example , allyl . in the definitions of r 1 , r 2 and r 3 , the lower alkyl group is straight - chain or branched alkyl groups having 1 to 3 carbon atoms , namely , methyl , ethyl , n - propyl and i - propyl . compound ( i ) and its process for production thereof are substantially disclosed in japanese published unexamined patent application no . 108858 / 1980 . preferable examples of compound ( i ) as an effective component for the anticonvulsive composition of the present invention are shown below : compound ( i ) has a low toxicity and a strong anticonvulsive action , which will be obvious from examples . above all , the following compounds under compounds ( i ) have an especially strong anticonvulsive action : ( 1 ) compounds ( i ) wherein a is a methyl group , and b is ## str7 ## [ wherein y 1 &# 39 ; is a halogen atom ( especially a chlorine atom ), a nitro group , an amino group , a trifluoromethyl group or a lower alkoxycarbonyl group ( especially an ethoxycarbonyl group ), and y 2 and y 3 have the same meanings as defined in the formula ( i )] or a naphthyl group . in the above , compounds wherein 1 y 2 and y 3 are hydrogen atoms , or 2 y 1 &# 39 ; is a halogen atom ( especially a chlorine atom ), y 2 is a hydrogen atom and y 3 is a halogen atom ( especially a chlorine atom ) at 3 , 4 or 5 positions are especially preferred . ( 2 ) compounds ( i ) wherein b is a hydrogen atom or a methyl group , and a is ## str8 ## [ wherein y 1 &# 34 ; is a trifluoromethyl group at 3 - position , or a halogen atom ( especially a chlorine atom ), an amino group or a trifluoromethyl group at 4 - position , and y 2 and y 3 have the same meanings as defined in the formula ( i )]. in the above , compounds wherein ○ 1 y 2 and y 3 are hydrogen atoms , or ○ 2 y 1 &# 34 ; is a halogen atoms at 4 - position , y 2 is a hydrogen atom and y 3 is a halogen atom ( especially a chlorine atom ) or a methyl group at 2 or 3 position are especially preferred . ( 4 ) compounds ( i ) wherein r 1 , r 2 and r 3 are hydrogen atoms . when compound ( i ) is used as an anticonvulsive agent , a daily dosage of 100 to 800 mg / 60 kg is usually administered wholly at a time , or separately twice or three times . tablets , granules , powder , capsules , syrup , injection , etc . prepared in the ordinary manner are used , depending on the administration purpose and administration mode . for example , when it is used in the form of tablets , it is preferable to use tablets containing 1 to 85 % by weight of the active component per tablet . in preparation of tablets , vehicles ( for example , lactose , glucose , sucrose , mannitol , light anhydrous silicic acid , etc . ), disintegrators ( for example , starch , sodium alginate , carboxymethylcellulose calcium , crystalline cellulose , sugar ester , etc . ), lubricants ( for example , magnesium stearate , talc , etc . ), binders ( for example , syrup , gelatin solution , polyvinyl alcohol , polyvinylpyrolidone , etc . ), dispersing agents ( for example , methylcellulose , etc . ), plasticizers ( for example , glycerin , etc . ), coating materials ( for example , hydroxypropylcellulose , etc . ), pigments , etc . are used according to the ordinary procedure . the present invention will be described in detail below , referring to examples . groups of mice , each consisting of 5 male dd - strain mice having a weight of 20 ± 1 g were orally administered with some of said compounds and 60 minutes thereafter , an electric current of 2 , 000 v , 50 ma was passed to both eyes of the mouse for 0 . 2 seconds to observe occurrence of tonic extensor . suppression of tonic extensor occurrence on at least three mice was regarded as effective , and med ( minimum effective dose ) for suppressing the convulsion was determined . groups of mice , each consisting of 5 male dd - strain mice having a weight of 20 ± 1 g were subcutaneously administered by 120 mg / kg of pentetrazol , and occurrence of clonic seizure was observed . suppression of clonic seizure occurrence on at least three mice was regarded as effective , and med was determined . table 1______________________________________ med for anticonvulsive action ( mg / kg , p . o .) maximal electroshock pentetrazol - inducedcompound seizure test seizure test______________________________________no . 3 75 200 7 100 10024 100 100 9 150 20029 150 15034 150 30031 100 10033 100 30036 100 20047 100 200______________________________________ the present test was performed in male carworth farm mice . all compounds were tested at least 3 dose levels ( 30 , 100 , 300 mg / kg ) with a fourth dose of 600 mg / kg being performed when there was sufficient quantity available . the vehicles used to solubilize each compound were 30 % aqueous polyethylene glycol solution ( compound nos . 31 to 38 , 45 , 47 and 48 ) and 0 . 9 % saline ( compound nos . 44 and 46 ). maximal electroshock seizures were elicited with a 60 cycle alternating current of 50 ma intensity ( 5 - 7 times that necessary to elicit minimal electroshock seizures ) delivered for 0 . 2 sec via corneal electrodes . a drop of 0 . 9 % saline was instilled in the eye prior to application of the electrodes in order to prevent the death of the animal . abolition of the hind limb tonic extension component of the seizure was defined as protection and results were expressed as : ## equ1 ## first , 85 mg / kg of pentylenetetrazole ( produces seizures in greater than 95 % of mice ) was administered as a 0 . 5 % solution subcutaneously in the posterior midline . the animal was observed for 30 minutes . failure to observe even a threshold seizure ( a single episode of clonic spasms of at least 5 sec duration ) was defined as protection and the results were expressed as : ## equ2 ## all results were classified into one of the following three evaluation standard : ○ 2 anticonvulsant activity at doses greater than 100 mg / kg , or anticonvulsant activity at 100 mg / kg not reinforced by similar activity at 300 mg / kg ○ 3 no anticonvulsant activity at doses up to and including 300 mg / kg table 2______________________________________compound no . evaluation compound no . evaluation______________________________________31 ○ 1 38 ○ 232 ○ 2 44 ○ 133 ○ 1 45 ○ 234 ○ 1 46 ○ 235 ○ 2 47 ○ 136 ○ 1 48 ○ 137 ○ 2______________________________________ groups of mice , each consisting of 3 to 6 male dd - strain mice having a weight of 20 ± 1 g were orally administered with suspension of some of said compounds in 0 . 3 % cmc solution , and 7 days after the administration lethal states were observed to determine ld 50 . table 3______________________________________compound ld . sub . 50 ( mg / kg , p . o .) ______________________________________no . 3 & gt ; 300 7 & gt ; 100024 & gt ; 300 9 & gt ; 30029 & gt ; 30034 & gt ; 30031 & gt ; 30033 & gt ; 30036 & gt ; 30047 & gt ; 300______________________________________ according to the ordinary procedure , 10 , 000 tablets having the following composition were prepared , where one tablet contained 50 mg of the effective component . ______________________________________1 -( 4 - chlorophenyl )- 3 - methyl - dihydrouracil 500 g ( compound no . 3 ) lactose 343 gcarboxymethylcellulose calcium 93 gmagnesium stearate 4 gtalc 8 gpolyvinyl alcohol 25 gglycerine 2 gtar pigment a trace 975 g______________________________________ according to the ordinary procedure , 10 , 000 tablets having the following composition were prepared , where one tablet contained 50 mg of the active component . ______________________________________main chemical ( compound no . 7 ) 500 glactose 980 gstarch 520 ghydroxyprophylcellulose 80 gmagnesium stearate 20 gtar pigment a trace 2100 g______________________________________ according to the ordinary procedure , 10 , 000 tablets having the following composition were prepared , where one tablet contained 50 mg of the active component . ______________________________________main chemical ( compound no . 24 ) 500 glight anhydrous silicic acid 20 gcrystalline cellulose 640 glactose 1020 gmagnesium stearate 20 gtar pigment a trace 2200 g______________________________________ at first , 8 g ( 0 . 032 moles ) of n -( methylcarbamoyl )- n -( 4 - chlorophenyl )- β - alanine was added to a mixed solution of 100 ml of 6n hydrochloric acid and 50 ml of acetic acid , and the mixture was refluxed wih heating for two hours . after the completion of reaction , 300 ml of water was added to the reaction mixture . the reaction mixture was left standing in a cold place , and precipitated crystals were recovered therefrom by suction filtration and recrystallized from 70 ml of ethyl acetate and 100 ml of n - hexane , whereby 4 . 8 g of the desired compound was obtained as crystals having a melting point of 145 ° to 146 ° c . ( yield : 64 . 6 %). at first , 32 g ( 0 . 1 mole ) of n -( methylcarbamoyl )- n -( 3 - trifluoromethylphenyl )- β - alanine was added to a mixed solution of 100 ml of 6n hydrochloric acid and 50 ml of acetic acid , and the mixture was refluxed with heating for two hours . after the completion of reaction , 300 ml of water was added to the reaction mixture . the reaction mixture was left standing in a cold place , and precipitated crystals were recovered therefrom by suction filtration and recrystallized from 70 ml of ethyl acetate and 100 ml of n - hexane , whereby 16 . 2 g of the desired compound was obtained as crystals having a melting point of 124 ° to 125 ° c . ( yield : 60 . 4 %). at first , 8 . 7 g ( 0 . 027 moles ) of n -( 2 , 5 - dichlorophenylcarbamoyl )- n - methyl - β - alanine was added to 50 ml of thionyl chloride and the mixture was refluxed with heating for one hour . after the completion of reaction , excess thionyl chloride was removed therefrom by distillation under reduced pressure , and then 100 ml of ethyl acetate was added to the residue . the mixture was washed with a saturated aqueous sodium bicarbonate solution twice and then with water , and dried over anhydrous sodium sulfate . after removal of the solvent therefrom by distillation under reduced pressure , precipitated crystals were recrystallized from 100 ml of ethyl acetate and 100 ml of n - hexane , whereby 6 . 6 g of the desired compound was obtained as crystals having a melting point of 120 . 5 ° to 123 ° c . ( yield : 80 . 9 %). at first , 8 . 0 g ( 0 . 03 moles ) of n -( 2 - methyl - 4 - chlorophenylcarbamoyl )- n - methyl - β - alanine was added to 250 ml of acetic anhydride , and the mixture was refluxed with heating for 2 . 5 hours . acetic anhydride was removed therefrom by distillation under reduced pressure , and precipitated crystals were recrystallized from 60 ml of ethyl acetate and 150 ml of n - hexane , whereby 1 . 8 g of the desired compound was obtained as crystals having a melting point of 120 ° to 127 ° c . ( yield : 24 . 1 %). at first , 8 . 7 g ( 0 . 03 moles ) of n -( 2 - chlophenylcarbamoyl )- n - methyl - β - analine was suspended in 50 ml of ethyl acetate , and 10 . 7 ml ( 0 . 15 moles ) of thionyl chloride was added to the suspension . the mixture was stirred at room temperature for 6 hours , and then 50 ml of n - hexane was added thereto . the mixture was left standing in a cold place overnight , and precipitated crystals were recovered therefrom by suction filtration , washed with n - hexane and dried , whereby 6 . 6 g of the desired compound was obtained as crystals having a melting point of 120 . 5 ° to 123 ° c . ( yield : 80 . 9 %). at first , 7 . 44 g ( 0 . 03 moles ) of n -( 2 , 4 - dichlorophenyl )- β - alanine methyl ester was dissolved in 150 ml of tetrahydrofuran ( thf ), and 19 . 2 ml ( 0 . 03 moles ) of n - butyl lithium was added thereto at - 78 ° c . several minutes thereafter , 5 . 4 ml ( 0 . 045 moles ) of methyl isocyanate was added thereto . the mixture was stirred at the same temperature for one hour , a saturated aqueous ammonium chloride solution was added thereto , and the mixture was extracted with ethyl acetate . the ethyl acetate layer was washed with water and with a saturated aqueous sodium chloride solution , and dried over anhydrous magnesium sulfate , and the solvent was distilled off under reduced pressure . the residue was subjected to silica gel column chromatography and recrystallized from toluene , whereby 1 . 32 g of the desired compound was obtained as colorless prism crystals having a melting point of 154 °- 157 ° c . ( yield : 16 . 1 %). at first , 7 g ( 0 . 032 moles ) of n - methoxycarbonyl - 2 , 3 - dichloroaniline was dissolved in 150 ml of anhydrous toluene , and 3 . 84 ml ( 0 . 038 moles ) of trichlorosilane and 6 . 6 ml ( 0 . 048 moles ) of triethylamine were added thereto . the mixture was stirred at 80 ° c . for one hour . after excess of trichlorosilane was distilled off under reduced pressure , 3 . 2 g ( 0 . 038 moles ) of n - methyl - β - alanine - nitrile was added thereto and the mixture was stirred at room temperature for one hour . ethyl acetate was added thereto , and the mixture was washed successively with 3n - aqueous hydrochloric acid solution , with water and with a saturated aqueous sodium chloride . the mixture was then dried over anhydrous magnesium sulfate and the solvent was distilled off under reduced pressure . the residue was subjected to silica gel column chromatography and recrystallized from toluene - n - hexane , whereby 4 . 12 g of n -( 2 , 3 - dichlorophenylcarbamoyl )- n - methyl - β - alaninenitrile was obtained as colorless prism cyrstals having a melting point of 97 ° c . ( yield : 47 . 4 %). then , 3 . 5 g ( 0 . 013 moles ) of the n -( 2 , 3 - dichlorophenyl - carbamoyl )- n - methyl - β - alaninenitrile was added to a solution consisting of 30 ml of 6n - hydrochloric acid and 10 ml of acetic acid , and the mixture was refluxed with heating for 4 hours . after completion of the reaction , 50 ml of water was added thereto . the deposited crystals were recovered by filtration with suction and recrystallized from ethyl acetate - n - hexane , whereby 2 . 43 g of 1 - methyl - 3 -( 2 , 3 - dichlorophenyl )- dihydrouracil was obtained as light yellow crystals having a melting point of 163 °- 165 ° c . ( yield : 69 . 4 %). at first , 4 g ( 0 . 014 moles ) of n -( methylcarbamoyl )- n -( 4 - trifluoromethylphenyl )- β - alanine was added to a solution consisting of 45 ml of 6n - hydrochloric acid and 15 ml of acetic acid , and the mixture was refluxed with heating for 2 hours . after completion of the reaction , 50 ml of water was added thereto . the deposited crystals were recovered by filtration with suction and recrystallized from ethyl acetate - n - hexane , 3 . 38 g of the desired compound was obtained as colorless needle crystals having a melting point of 115 °- 117 ° c . ( yield : 90 . 1 %). in this example , 1 . 16 g ( yield : 15 %) of the desired compound as colorless prism crystals having a melting point of 122 °- 125 ° c . was obtained from 7 g ( 0 . 032 moles ) of n - methoxycarbonyl - 2 , 4 - dichloroaniline and 4 . 0 g ( 0 . 048 moles ) of n - methyl - β - alaninenitrile according to the same manner as in reference example 7 . in this example , 3 . 75 g ( yield : 73 . 8 %) of the desired compound as crystals having a melting point of 228 °- 229 ° c . was obtained from 5 g ( 0 . 02 moles ) of n -( α - naphthylcarbamoyl )- n - methyl - β - alaninenitrile according to the same manner as in reference example 8 .