the present invention is directed to a process for preparing enantiomerically enriched 1 - amino - 4 -( hydroxymethyl ) cyclopent - 2 - ene derivatives of the general formulae wherein r 1 is hydrogen or an optionally substituted c 1 - 8 - alkyl radical , aryl radical or cycloalkyl radical and r 2 is acyl , and wherein a racemic 1 - amino - 4 -( hydroxymethyl ) cyclopent - 2 - ene derivative of the general formula : in which r 1 is as defined above is reacted using a hydrolase in the presence of an acylating agent . another embodiment of the present invention is directed to a process for preparing enantiomerically enriched 1 - amino - 4 -( hydroxymethyl ) cyclopent - 2 - ene derivatives of the general formula in which r 1 , as defined in claim 1 ; using a hydrolase in the presence of an acylating agent into enantiomerically enriched wherein r 1 and r 2 , as defined in claim 1 ; and b ) chemically hydrolyzing the 1 - amino - 4 -( hydroxymethyl ) cyclopent - 2 - ene derivatives of the general formula i into the corresponding enantiomers of the general formula ii . a further embodiment of the present invention is directed to a process for preparing enantiomerically enriched 1 - amino - 4 -( hydroxymethyl ) cyclopent - 2 - ene of the formula wherein r 1 , as defined in claim 1 , using a hydrolase in the presence of an acylating agent into enantiomerically enriched wherein r 1 and r 2 , as defined in claim 1 ; and b ) chemically hydrolyzing the 1 - amino - 4 -( hydroxymethyl ) cyclopent - 2 - ene derivatives of the general formulae i and ii the starting materials , the racemic 1 - amino - 4 -( hydroxymethyl ) cyclopent - 2 - ene derivatives of the general formula iii , can be prepared starting from (±)- 2 - azabicyclo [ 2 . 2 . 1 ] hept - 5 - ene - 3 - one , in accordance with wo 97 / 45529 . preference is given to using the cis - racemic starting materials . the term alkyl , as used in this context , includes both linear and branched alkyl . alkyl can be substituted or unsubstituted . c 1 - 8 - alkyl is in particular methyl , ethyl , propyl , isopropyl , butyl , tert - butyl , pentyl and its isomers , hexyl and its isomers , heptyl and its isomers or octyl and its isomers . substituted c 1 - 8 - alkyl is understood as c 1 - 8 - alkyl which is substituted by one or more halogen atoms , by or 3 or by nr 3 r 4 , r 3 and r 4 being identical or different and being hydrogen or branched or linear c 1 - 8 - alkyl , aryl or cycloalkyl . the halogen atom used may be f , cl , br or i . examples of nr 3 r 4 s are methylamino , n - methyl - n - ethylamino , 1 - piperidinyl or aminomethyl . examples of or 3 s are methoxy , methoxymethyl , ethoxy , propoxy and phenoxy . aryl is preferably understood as benzyl or phenyl , substituted or unsubstituted . substituted aryl is understood hereinbelow as aryl which is substituted by one or more halogen atoms c 1 - 4 - alkyl groups , c 1 - 4 - alkoxy groups , amino , cyano or nitro groups . the substituted benzyl used is preferably chloro - or bromobenzyl , and the substituted phenyl used is preferably bromo - or chlorophenyl . cycloalkyl is advantageously substituted or unsubstituted c 3 - 7 - cycloalkyl , for example cyclopropyl , cyclopentyl or cyclohexyl . examples of suitable substituents are those mentioned for aryl . acyl is preferably c 1 - 6 - alkanoyl , unsubstituted or substituted by one or more halogen atoms , c 1 - 4 - alkoxy , aryl , hydroxy , amino , cyano , nitro , and / or coor , where r is c 1 - 4 - alkyl . examples of unsubstituted or substituted acyl radicals are acetyl , propionyl , butyryl , chloroacetyl , bromoacetyl , dichloroacetyl , cyanoacetyl , methoxycarbonyl , ethoxycarbonyl , methoxyethanoyl , hydroxybutyroyl , hydroxyhexanoyl , phenylcarbonyl , chlorophenylcarbonyl and benzylcarbonyl . suitable acylating agents are , in general , carboxylic acid derivatives , such as carboxamides , carboxylic anhydrides or carboxylic esters . the carboxylic esters used may be alkoxycarboxylic esters , such as ethyl methoxyacetate , or propyl methoxyacetate , c 1 - 6 - carboxylic esters , such as butyl acetate , ethyl butyrate , phenyl butyrate , trichloroethyl butyrate , ethyl hexanoate , vinyl butyrate , glycerol esters , such as tributyrin ( glyceryl tributyrate ), glycol esters , such as glycol dibutyrate , diethyl diglycolate , or dicarboxylic esters , such as vinyl succinate , cyano - substituted esters , such as cyanoacetic esters , or cyclic carboxylic esters , such as butyrolactone , caprolactone . the carboxamides used may be the amides which correspond to the abovementioned esters . the carboxylic anhydrides used may be simple , mixed or cyclic anhydrides , such as butyric anhydride , acetyl benzoate , succinic anhydride . the hydrolases used may be lipases , esterases or proteases . suitable for use as lipase are customary lipases , such as , for example , novo - lipase sp523 from aspergillus oryzae ( novozym 398 ), novo - lipase sp524 from aspergillus oryzae ( lipase = palatase 20000l from novo ), novo - lipase sp525 from candida antarctica ( lipase b novozym 435 , immobilized ), novo - lipase sp526 from candida antarctica ( lipase a = novozym 735 , immobilized ), lipase kits from fluka ( 1 & amp ; 2 ), amano p lipase , lipase from pseudomonas sp ., lipase from candida cylindracea , lipase from candida lipolytica , lipase from mucor miehei , lipase m from mucor javanicus ( amano ), lipase from aspergillus niger , lipase from bacillus thermocatenulatus , lipase from candida antarctica , lipase ah ( amano ; immobilized ), lipase p ( nagase ), lipase ay from candida rugosa , lipase g ( amano 50 ), lipase f ( amano f - ap15 ), lipase ps ( amano ), lipase ah ( amano ), lipase d ( amano ), lipase ak from pseudomonas fluorescens , lipase ps from pseudomonas cepacia , newlase i from rhizopus niveus , lipase ps - ci ( immobilized lipase from pseudomonas cepacia ). these lipases can be used , as is known to the person skilled in the art , as cell - free enzyme extracts or else in the corresponding microorganism cell . suitable proteases are likewise commercially available proteases , for example serine proteases such as subtilisin . the subtilisin used may be , for example , savinase from bacillus sp ., alcalase , subtilisin from bacillus licheniformis and proteases from aspergillus , rhizopus , streptomyces or bacillus sp . depending on which hydrolase is selected , one of the two enantiomers of a racemic , for example cis - racemic , 1 - amino - 4 -( hydroxymethyl ) cyclopent - 2 - ene of the formula iii is acylated ( compounds of the formula i ), whereas the other enantiomer remains unchanged ( compounds of the formula ii ). the two enantiomers can then be separated . different hydrolases may have different stereospecificities . if , for example , cis - n - acetyl - 1 - amino - 4 -( hydroxymethyl ) cyclopent - 2 - ene is reacted with lipase m and an acylating agent , the ( 1r , 4s )- enantiomer is acylated specifically and can be separated from the non - acylated ( 1s , 4r )- enantiomer . if the hydrolase used is , for example , savinase ( protease from bacillus sp . ), the ( 1s , 4r )- enantiomer is acylated specifically , whereas the ( 1r , 4s )- enantiomer remains . the hydrolase - catalyzed acylation is advantageously carried out at a temperature of from 0 to 70 ° c ., preferably at a temperature of from 15 to 45 ° c . the hydrolase - catalyzed acylation can be carried out in a protic or aprotic organic solvent . suitable aprotic organic solvents are ethers , aliphatic hydrocarbons , organic bases and carboxylic acid derivatives . ethers which may be used are tert - butyl methyl ether , diisopropyl ether , dibutyl ether , dioxane or tetrahydrofuran . suitable aliphatic hydrocarbons are hexane , heptane , octane . suitable organic bases are pyridines or trialkylamines , such as triethylamine . possible carboxylic acid derivatives are , for example , ethyl acetate or the above - described acylating agents . the enantiomerically enriched 1 - amino - 4 -( hydroxymethyl ) cyclopent - 2 - ene derivatives of the general formula i or ii formed in the hydrolase - catalyzed acylation can , after separation , be directly chemically hydrolyzed into the corresponding enantiomerically enriched 1 - amino - 4 -( hydroxymethyl )- cyclopent - 2 - ene isomers of the formula iv alternatively , the enantiomerically enriched 1 - amino - 4 -( hydroxymethyl ) cyclopent - 2 - ene derivative of the general formula i which has been separated off can initially , by choosing the appropriate hydrolysis conditions , be hydrolysed step - wise back to the corresponding enantiomerically enriched 1 - amino - 4 -( hydroxymethyl ) cyclopent - 2 - ene derivative of the general formula ii which , if desired , is then converted by further chemical hydrolysis as above into the corresponding enantiomerically enriched 1 - amino - 4 -( hydroxymethyl ) cyclopent - 2 - ene of the formula iv . advantageously , the chemical hydrolysis is carried out using an alkali metal hydroxide or ammonia . the alkali metal hydroxide used may be sodium hydroxide or potassium hydroxide . the chemical hydrolysis can be carried out at a temperature of from 20 to 100 ° c ., preferably at a temperature of from 60 to 80 ° c . the preferred enantiomerically enriched 1 - amino - 4 -( hydroxymethyl ) cyclopent - 2 - ene derivative of the general formula i is the ( 1r , 4s )- and ( 1s , 4r )- n - acetyl - 1 - amino - 4 -( propylcarbonyloxymethyl ) cyclopent - 2 - ene ( r 1 = ch 3 , r 2 = propylcarbonyl ), and the preferred 1 - amino - 4 -( hydroxymethyl ) cyclopent - 2 - ene derivatives of the general formula ii are the ( ir , 4s )- and ( 1s , 4r )- n - acetyl - 1 - amino - 4 -( hydroxymethyl ) cyclopent - 2 - ene , which are then chemically hydrolyzed preferably into the ( ir , 4s )- or ( 1s , 4r )- 1 - amino - 4 -( hydroxymethyl ) cyclopent - 2 - ene . 50 mg of cis - n - acetyl - 1 - amino - 4 -( hydroxymethyl ) cyclopent - 2 - ene and 250 μl of vinyl butyrate were dissolved in 5 ml of 2 - methyl - 2 - butanol . 300 mg of lipase m ( from mucor javanicus ; amano ) were added , and the suspension was stirred at room temperature . after 16 h , ( 1s , 4r )- n - acetyl - 1 - amino - 4 -( hydroxymethyl ) cyclo - pent - 2 - ene was present in an enantiomeric excess of 98 . 5 % ( gc ). after separating ( 1s , 4r )- n - acetyl - 1 - amino - 4 -( hydroxymethyl ) cyclopent - 2 - ene and the ( 1r , 4s )- n - acetyl - 1 - amino - 4 -( propylcarbonyloxymethyl ) cyclopent - 2 - ene formed ( chromatography over silica gel 60 ), the two compounds were separately taken up in 2m aqueous sodium hydroxide solution . ( 1s , 4r )- n - acetyl - 1 - amino - 4 -( hydroxymethyl ) cyclopent - 2 - ene was converted by stirring at 80 ° c . ( 70 h ), into the enantiomerically pure or enantiomerically enriched cis - 1 - amino - 4 -( hydroxymethyl ) cyclopent - 2 - ene while ( 1r , 4s )- n - acetyl - 1 - amino - 4 -( propylcarbonyloxymethyl ) cyclopent - 2 - ene was converted by stirring at room temperature ( 5 h ) into the enantiomerically pure or enantiomerically enriched cis - n - acetyl - 1 - amino - 4 -( hydroxymethyl ) cyclopent - 2 - ene . 10 mg of cis - n - acetyl - 1 - amino - 4 -( hydroxymethyl ) cyclopent - 2 - ene and 50 μl of vinyl butyrate were dissolved in 1 ml of dioxane . 30 mg of lipase m ( from mucor javanicus ; amano ) were added , and the suspension was stirred at room temperature . after 20 h , ( 1s , 4r )- n - acetyl - 1 - amino - 4 -( hydroxymethyl ) cyclopent - 2 - ene was present in an enantiomeric excess of 91 . 0 % ( gc ). 10 mg of cis - n - acetyl - 1 - amino - 4 -( hydroxymethyl ) cyclopent - 2 - ene and 50 μl of vinyl butyrate were dissolved in 1 ml of 2 - methyl - 2 - butanol . 40 mg of savinase ( protease from bacillus sp . ; novo nordisk ) were added , and the suspension was stirred at room temperature . after 20 h , ( 1r , 4s )- n - acetyl - 1 - amino - 4 -( hydroxymethyl ) cyclopent - 2 - ene was present in an enantiomeric excess of 91 . 7 % ( gc ). 10 mg of cis - n - acetyl - 1 - amino - 4 -( hydroxymethyl ) cyclopent - 2 - ene and 50 μl of vinyl butyrate were dissolved in 1 ml of dioxane . 40 mg of savinase ( protease from bacillus sp . ; novo nordisk ) were added , and the suspension was stirred at room temperature . after 200 h , ( 1r , 4s )- n - acetyl - 1 - amino - 4 -( hydroxy - methyl ) cyclopent - 2 - ene was present in an enantiomeric excess of 81 . 7 % ( gc ). 100 mg of cis - n - acetyl - 1 - amino - 4 -( hydroxymethyl ) cyclopent - 2 - ene and 0 . 5 mmol of vinyl butyrate were dissolved in 1 ml of 2 - methyl - 2 - butanol . 20 mg of lipase ps ( from pseudomonas cepacia ) were added , and the suspension was stirred at room temperature . after 21 h , ( 1r , 4s )- n - acetyl - 1 - amino - 4 -( hydroxymethyl )- cyclopent - 2 - ene is present in an enantiomeric excess of 44 % ( gc ). 10 mg of cis - n - acetyl - 1 - amino - 4 -( hydroxymethyl ) cyclopent - 2 - ene and 0 . 03 mmol of tributyrin were dissolved in 1 ml of 2 - methyl - 2 - butanol . 20 mg of lipase ps ( pseudomonas cepacia ) were added , and the suspension was stirred at room temperature . after 200 h , ( 1r , 4s )- n - acetyl - 1 - amino - 4 -( hydroxymethyl )- cyclopent - 2 - ene is present in an enantiomeric excess of 32 % ( gc ).