the present invention relates to the production of chiral compounds having utility as intermediates in the synthesis of d - threo - methylphenidate by enzymatic and microbial resolution of racemic lactams , amides , esters , and nitriles to yield d - threo - 2 -( piperid - 2 - yl )- 2 - phenyl - acetic acid , commonly known as ( d )- ritalinic acid , and their functional optically active acid derivatives such as esters and amides . more specifically , the present invention relates to the formation of d - threo - 2 -( piperid - 2 - yl )- 2 - phenyl acetic acids through enzymatic conversion of compounds of the formula ( i ): ## str2 ## wherein : { i } r 1 and r 2 are hydrogen , and r 3 is carbamoyl ; { ii } r 1 and r 3 taken together are carbonyl , and r 2 is hydrogen ; { iii } r 3 is cyano , and r 1 and r 2 are hydrogen ; or { iv } r 1 and r 2 are hydrogen and r 3 is carboxy methyl . in another embodiment the unreacted racemic lactam , amide , or nitrile of formula ( i ) may be first biocatalytically enriched to high enantiomeric excess and subsequently converted to the optically pure ( d )- ritalinic acid . in either case , the resultant d - threo - 2 -( piperid - 2 - yl )- 2 - phenyl acetic acid intermediate can then be esterified according to known techniques to yield ( d )- threo - methylphenidate . in another embodiment , the d1 - threo - 2 -( piperid - 2 - yl )- 2 - phenyl acetic acid methyl ester may be enriched by action of an esterase directly to d - threo - 2 -( piperid - 2 - yl )- 2 - phenyl acetic acid methyl ester ( d - threo - methylphenidate ) substantially free of the 1 - isomer , and recovered . in a first embodiment , wherein r 1 and r 2 are hydrogen , and r 3 is carbamoyl ( i . e ., conh 2 ), the compound is converted to d - threo - 2 -( piperid - 2 - yl )- 2 - phenyl acetic acid substantially free of the 1 - isomer by action of an amidase . in a second embodiment , wherein r 1 and r 3 taken together are carbonyl , and r 2 is hydrogen , the compound is converted to d - threo - 2 -( piperid - 2 - yl )- 2 - phenyl acetic acid substantially free of the 1 - isomer by action of an amidase or lactamase . in a third embodiment , wherein r 3 is cyano , and r 1 and r 2 are hydrogen , the compound is converted to d - threo - 2 -( piperid - 2 - yl )- 2 - phenyl acetic acid substantially free of the 1 - isomer by action of a nitrilase . in a fourth embodiment , wherein r 3 is cyano , and r 1 and r 2 are hydrogen , the compound can be converted to the amide by the action of a nitrile hydratase , which amide is then converted to d - threo - 2 -( piperid - 2 - yl )- 2 - phenyl acetic acid substantially free of the 1 - isomer by action of an amidase . in yet another embodiment , wherein r 1 and r 2 are hydrogen and r 3 is carboxy methyl ( i . e ., cooch ), the compound can be enriched directly to d - threo - 2 -( piperid - 2 - yl )- 2 - phenyl acetic acid methyl ester substantially free of the 1 - isomer by action of an esterase . the present invention also relates to novel lactams useful as intermediates in the production of d - threo - 2 -( piperid - 2 - yl )- 2 - phenyl acetic acid and derivatives thereof , and methods for producing the same . the term &# 34 ; enantiomeric enrichment &# 34 ; as used herein refers to the increase in the amount of one enantiomer as compared to the other . this can involve ( i ) a decrease in the amount of one chiral form as compared with the other , ( ii ) an increase in the amount of one chiral form as compared with the other , or ( iii ) a decrease in the amount of one chiral form and an increase in the amount of the other chiral form . a &# 34 ; substantial amount &# 34 ; of conversion as used herein is defined as being at least 50 % by weight of enantiomeric conversion . the term , &# 34 ; substantially free of the 1 - isomer &# 34 ; means that the composition contains at least 90 % by weight of d - threo - 2 -( piperid - 2 - yl )- 2 - phenyl acetic acid , and 10 % by weight of 1 - threo - 2 -( piperid - 2 - yl )- 2 - phenyl acetic acid or derivative thereof . in the most preferred embodiment , the term &# 34 ; substantially free of the 1 - isomer &# 34 ; means that the composition contains at least 99 % by weight of d - threo - 2 -( piperid - 2 - yl )- 2 - phenyl acetic acid and 1 % or less of 1 - threo - 2 -( piperid - 2 - yl )- 2 - phenyl acetic acid or derivative thereof . the lactamases or cyclicamidases , nitrilases , nitrile hydratases , and esterases described herein can be obtained from microorganisms of the genera alcaligenes , pseudomonas , rhodopseudomonas , corynebacterium , escherichia , arthrobacter , aspergillus , acinetobacter , brevibacterium , bacillus , mycobacterium , rhodococcus , agrobacterium , botrytis , candida , chaetomium , chromobacterium , cladosporium , enterobacter , microbacteriumr mucor , nocardia , ophiobolus , penicillium , rhizopus , rhodotorula , saccharomyces , staphylococcus , streptomyces , torulopsis , and trichoderma , or preparations thereof . more preferably , the lactamases or cyclicamidases , nitrilases , nitrile hydratases , and esterases described herein can be obtained from pseudomonas cepacia , acinetobacter baumanni , pseudomonas putida , alcaligenes faecalis , agrobacterium radiobacter , aspergillus niger , chromobacterium violaceum , escherichia coli , gotrichum candidum , humicola lanuginosa , mycobacterium phlei , nocardia asteroides , nocardia erythropolis , penicillium cyclopium , pseudomonas fluorescens , pseudomonas ovalis , pseudomonas putida , rhizopus niveus , rhizopus oryzae , staphylococcus aureus , streptomyces clavuligerus , rhodococcus rhodocris or streptomyces griseus . the actual enzymatic conversion can be effected by conventional culturing techniques in the presence of the compound of formula ( i ), with isolated but non - growing cells , or by bringing the compounds into contact with a soluble enzyme preparation . the enzymes described herein can be in free form , either as a cell free extract or a whole cell preparation , or immobilized on a suitable support or matrix such as cross - linked dextran or agarose , silica , polyamide or cellulose . they can also be encapsulated in polyacrylamide , alginates , fibers , or the like . methods for such immobilization are described in the literature ( see , e . g ., methods of enzymology , 44 , 1976 ). procedures and materials used herein are described below , followed by typical examples . a suitable salt medium for the microbiological transformations described in the following examples has the following composition : ______________________________________media a : ______________________________________mgso . sub . 4 1 . 00 g / lcacl . sub . 2 0 . 021 g / lznso . sub . 4 . 7h . sub . 2 o 0 . 20 mg / lmnso . sub . 4 . 4h . sub . 2 o 0 . 10 mg / lh . sub . 3 bo . sub . 3 0 . 02 mg / lcuso . sub . 4 . 5h . sub . 2 o 0 . 10 mg / lcocl . sub . 2 . 6h . sub . 2 o 0 . 05 mg / lnicl . sub . 2 . 6h . sub . 2 o 0 . 01 mg / lfeso . sub . 4 1 . 50 mg / lnamoo . sub . 4 2 . 00 mg / lfe edta 5 . 00 mg / lkh . sub . 2 po . sub . 4 20 . 00 mg / lnaoh to ph 7______________________________________ the composition is not critical but is standardized for all procedures to eliminate it as a variable . a chemostat is maintained with 0 . 5 % ( w / v ) of 2 - phenyl - acetonitrile and 10 mm sodium pyruvate at a dilution rate of 03 / hr in media a . the chemostat is inoculated and run for approximately one month at 37 ° c . and ph 6 . 8 - 7 . 0 . strains which develop are isolated and grown on minimal media agar containing the standard salt medium ( media a ) supplemented with 10 mm of pyruvate and 5 mm ∝- aryl -∝- piperidyl - acetonitrile . microbial sources for an amidase or nitrile / amidase may also be enriched and isolated by use of shaker flasks maintained on media a , at ph 6 . 8 - 7 . 0 at 37 ° c . on an environmental shaker . the isolation technique is performed as above . lactamase is enriched and isolated as above using (±) trans - 7 - phenyl - 1 - azabicyclo ( 4 , 2 , 0 ) octan - 8 - one as the sole nitrogen source instead of 2 - phenylacetonitrile or ∝- aryl -∝- piperidyl - acetonitrile . unless otherwise indicated , cells from culture are centrifuged for 10 minutes at 10 , 000 g , resuspended in 10 mm of phosphate buffer at ph 7 and 0 . 5 mm of pyridoxal phosphate , and ruptured by two passes through a chilled french press operating at 15 , 000 psi . cell debris is removed by centrifugation for one hour at 10 , 000 g and the enzyme - containing supernatant collected . quantitative analysis of d1 - threo - ritalinic acid in biological liquids is performed according to the method of srinivas et al ., enantiomeric gas chromatography assay with electron capture detection for d1 - ritalinic acid in plasma , j . chromatagraph . 530 : 327 - 336 ( 1990 ). quantitative analysis of d1 - threo - methylphenidate in biological liquids is performed according to the method of srinivas et al ., stereoselective disposition of methylphenidate in children with attention deficit disorder , j . pharmacol . exp . ther ., 241 : 300 - 306 ( 1987 ). the following examples will serve to further typify the nature of the invention , but should not be construed as a limitation on the scope thereof , which is defined solely by the appended claims . lactamase is obtained from pseudomonas cepacia grown on 1 - 2 % penicillin as the sole carbon and nitrogen source in a minimal media . fifty milliliters of media a containing 2 g / l of penicillin and is inoculated with pseudomonas cepacia . after the mixture is incubated at 30 ° c . for 48 hours , 10 ml of the mixture are subcultured into 250 ml of media a with 2 g / l penicillin . after 40 hours of incubation at 30 ° c ., the cells are concentrated to a paste by centrifugation at 10 , 000 g and washed with 50 ml phosphate buffer ph 7 and again concentrated to a paste by centrifugation at 10 , 000 g . the washed paste then is passed through a french press at 17 , 000 psi to rupture the cells and produce cell extract . cell debris is removed by centrifugation for one half hour at 100 , 000 g and the enzyme - containing supernatant collected . racemic (±) trans - 7 - phenyl - 1 - azabicyclo ( 4 , 2 , 0 ) octan - 8 - one ( 0 . 5 g ) is added to a mixture of 20 ml of 50 mm potassium phosphate buffer ph 7 and 1 ml cell extract of lactamase . the reaction is maintained at 30 ° c . until the enantiomer excess as determined by chiral gas chromatography is no less than 98 % of d - ritalinic acid obtained , generally about 3 hours under these conditions . a lactamase with opposite stereoselectivity obtained from a microorganism such as rhodococcus rhodochrous can be used to resolve (±) trans - 7 - phenyl - 1 - azabicyclo ( 4 , 2 , 0 )- octan - 8 - one to 1 - ritalinic acid and the d - trans - 7 - phenyl - 1 - azabicyclo ( 4 , 2 , 0 )- octan - 8 - one . this lactam is then hydrolyzed to the d - ritalinic acid by conventional means . trans - 7 - phenyl - 1 - azabicyclo ( 4 , 2 , 0 ) - octan - 8 - one may be prepared by the method of corey , mol , or earle ( corey et al ., j . amer . chem . soc ., 87 : 2518 ( 1965 ); earle et al ., j . chem . soc . c . 2093 ( 1969 ); moll f . naturforsch ., teil b , 21 : 297 ( 1966 ). the reaction mixture prepared above is extracted with methylene chloride and the organic layer is dried with mgso 4 . the organic layer is then filtered and concentrated by rotary evaporation at 30 ° with reduced pressure , to yield an oil product . the oil product may be further purified by column chromatography . amidase is obtained from acinetobacter baumanni grown on 30 mm 2 - cyanobutane as the sole carbon and nitrogen source in a minimal media . fifty milliliters of media a containing 30 mm 2 - cyanobutane is inoculated with acinetobacter baumanni . after the mixture in incubated at 30 ° c . for 48 hours , 10 ml of the mixture are subcultured into 250 ml of media a with 30 mm 2 - cyanobutane . after 40 hours of incubation at 30 ° c ., the cells are concentrated to a paste by centrifugation at 10 , 000 g and washed with 50 ml phosphate buffer ph 7 . 5 and again concentrated to a paste by centrifugation at 10 , 000 g . the washed paste then is passed through a french press at 17 , 000 psi to rupture the cells and produce cell extract . cell debris is removed by centrifugation for one half hour at 100 , 000 g and the enzyme - containing supernatant collected . racemic threo - 2 -( piperid - 2 - yl )- 2 - phenyl - 2 - acetamide ( 0 . 5 g ) prepared by , e . g ., the method of hartmann ( u . s . pat . no . 2 , 507 , 631 ) is added to a mixture of 20 ml of 50 mm potassium phosphate buffer ph 8 and 1 ml cell extract of amidase . the reaction is maintained at 30 ° c . until the enantiomer excess as determined by chiral gas chromatography is no less than 98 % of d - ritalinic acid is obtained , generally about 5 hours under these conditions . an amidase with opposite stereoselectivity obtained from a microorganism such as rhodococcus rhodochrous can be used to resolve d1 - threo - 2 -( piperid - 2 - yl )- 2 - phenyl - acetamide to 1 - ritalinic acid and the d - threo - 2 -( piperid - 2 - yl )- 2 - phenyl - acetamide . this amide is then hydrolyzed to the d - ritalinic acid by conventional means . racemic trans - 7 - phenyl - 1 - azabicyclo ( 4 , 2 , 0 )- octan - 8 - one ( 0 . 5 g ) is added to a mixture of 20 ml 50 mm phosphate buffer ph 7 . 5 and 1 ml of pseudomonas putida cell extract . the reaction is maintained at 30 ° c . until the enantiomeric excess as determined by gas chromatography is not less than 98 % ritalinic acid is obtained , generally about 24 hours under these conditions . alternatively , a cell extract containing an amidase of opposite stereoselectivity may be used to effect a resolution of racemic trans - 7 - phenyl - 1 - aza - bicyclo ( 4 , 2 , 0 )- octan - 8 - one where 1 - ritalinic acid is produced and the d - lactam is isolated as the product . the reaction mixture prepared above is extracted with methylene chloride and the organic layer dried with mgso 4 . the organic layer is then filtered and concentration by rotary evaporation at 30 ° with reduced pressure , to yield an oil . the oil product may be further purified by column chromatography . nitrile hydratase and amidase are obtained from alcaligenes faecalis grown on 30 mm 2 - cyanobutane or 2 - phenylacetonitrile as the sole carbon and nitrogen source in a minimal media . fifty milliliters of media a containing 30 mm 2 - cyanobutane is inoculated with alcaligenes faecalis . after the mixture is incubated at 30 ° c . for 48 hours , 10 ml of the mixture are subcultured into 250 ml of media a with 30 mm 2 - cyanobutane or 2 - phenylacetonitrile . after 40 hours of incubation at 30 ° c ., the cells are concentrated to a paste by centrifugation at 10 , 000 g and washed with 50 ml phosphate buffer ph 7 . 5 and again concentrated to a paste by centrifugation at 10 , 000 g . the washed paste then is passed through a french press at 17 , 000 psi to rupture the cells and produce cell extract . cell debris is removed by centrifugation for one half hour at 100 , 000 g and the enzyme - containing supernatant collected . use of nitrile hydratase and amidase pathway to produce d - threo - 2 -( piperid - 2 - yl )- 2 - phenyl - acetic acid and 1 - threo - 2 -( piperid - 2 - yl )- 2 - phenyl - 2 - acetamide from d , 1 - threo - 2 -( piperid - 2 - yl )- 2 - phenyl - acetonitrile . racemic threo - 2 -( piperid - 2 - yl )- 2 - phenyl - 2 - acetonitrile ( 0 . 5 g ) is added to a mixture of 20 ml of 50 mm potassium phosphate buffer ph 8 and 1 ml cell extract of alcaligenes faecalis with nitrile hydratase and amidase activity . the reaction is maintained at 30 ° c . until the enantiomer excess as determined by chiral gas chromatography is no less than 98 % of d - ritalinic acid is obtained , generally about 5 hours under these conditions . the use of an esterase / lipase for the stereoselective enrichment of d1 - threo - α - phenyl - α - piperidyl - acetic acid methyl ester a microbial source of a stereoselective esterase or lipase may be obtained from commercial sources such as novo nordisk &# 39 ; s &# 34 ; humicola lipolase &# 34 ; or an atcc pseudomonas strain 31809 or 31808 . esterase / lipase is obtained from pseudomonas sp . atcc strain 31809 grown on 1 % olive oil in media a supplemented with 8 g / l nutrient broth . fifty milliliters of media a containing the 1 % olive oil and 8 g / l nutrient broth is inoculated with pseudomonas sp . atcc strain 31809 . after the mixture is incubated at 30 ° c . for 48 hours , 10 ml of the mixture are subcultured into 250 ml of media with 1 % olive oil supplemented with 8 g / l nutrient broth . after 24 hours of incubation at 30 ° c ., the cells are concentrated to a paste by centrifugation at 10 , 000 g and washed with 50 ml phosphate buffer ph 7 . 5 and again concentrated to a paste . cells are ruptured as above . d1 - threo - α - phenyl - α - piperidyl - acetic acid methyl ester ( 0 . 5 g ) prepared by the method of hartmann is added to a mixture of 20 ml of 50 mm potassium phosphate buffer ph 7 and 1 ml cell extract . the reaction is maintained at 30 ° c . until an enantiomeric excess as determined by chiral gc of no less than 98 % d - threo - methylphenidate is obtained , generally about 25 hours under these conditions .