a , together with x and the atoms to which x is bound , is a 4 - to 7 - membered aromatic or non - aromatic ring having up to 4 heteroatoms independently selected from n , nh , o , so , or so 2 ; wherein said ring is optionally fused to a ( c6 - c10 ) aryl , ( c5 - c10 ) heteroaryl , ( c3 - c10 ) cycloalkyl or ( c3 - c10 ) heterocyclyl ; wherein a has up to 3 substituents selected independently from j ; x is —[ ch 2 ] o —, —[ cj ′ j ′] o —, —[ ch 2 ] m — o —, —[ ch 2 ] m — s ( o ) 2 —, —[ ch 2 ] m — so —, —[ ch 2 ] m — s —, —[ cr 20 r 20 ] m — nr 21 —, or —[ cr 20 r 20 ] m — nj ″—, wherein : j is halogen , — or ′, — no 2 , — cf 3 , — ocf 3 , — r ′, oxo , — or ′, — o - benzyl , — o - phenyl , 1 , 2 - methylenedioxy , — n ( r ′) 2 , — sr ′, — sor ′, — so 2 r ′, — c ( o ) r ′, — coor ′, or — con ( r ′) 2 ; j ′ is halogen , — or ′, — no 2 , — cf 3 , — ocf 3 , — r ′, — or ′, — o - benzyl , — o - phenyl , 1 , 2 - methylenedioxy , — n ( r ′) 2 , — sr ′, — sor ′, — so 2 r ′, — c ( o ) r ′, — coor ′, or — con ( r ′) 2 ; j ′ is — or ′, — cf 3 , — ocf 3 , — r ′, oxo , — or ′, — o - benzyl , — o - phenyl , 1 , 2 - methylenedioxy , — n ( r ′) 2 , — sr ′, — sor ′, — so 2 r ′, — c ( o ) r ′, — coor ′, or — con ( r ′) 2 , wherein each r ′ is independently : hydrogen , —( c1 - c12 ) aliphatic , —( c3 - c10 ) cycloalkyl or - cycloalkenyl , —( c1 - c12 ) aliphatic -[( c3 - c10 ) cycloalkyl or - cycloalkenyl ], —( c6 - c10 ) aryl , —( c1 - c12 ) aliphatic -( c6 - c10 ) aryl , —( c3 - c10 ) heterocyclyl , —( c1 - c12 ) aliphatic -( c6 - c10 ) heterocyclyl , —( c5 - c10 )- heteroaryl , or —( c1 - c12 )- aliphatic -( c5 - c10 ) heteroaryl ; —( c1 - c12 ) aliphatic , —( c3 - c10 )- cycloalkyl or - cycloalkenyl , —( c1 - c12 )- aliphatic -[( c3 - c10 )- cycloalkyl or - cycloalkenyl ], —( c6 - c10 )- aryl , ( c1 - c12 ) aliphatic -( c6 - c10 ) aryl , —( c3 - c10 )- heterocyclyl , —( c1 - c12 ) aliphatic -( c6 - c10 ) heterocyclyl , —( c5 - c10 ) heteroaryl , or —( c1 - c12 ) aliphatic -( c5 - c10 ) heteroaryl , wherein each of r 1 and r 3 is independently and optionally substituted with up to 3 substituents independently selected from j ; wherein up to 3 aliphatic carbon atoms in r 1 and r 3 may be replaced by a heteroatom selected from o , nh , s , so , and so 2 in a chemically stable arrangement ; hydrogen , —( c1 - c12 ) aliphatic , —( c1 - c12 ) aliphatic -( c3 - c10 ) cycloalkyl , or —( c1 - c12 ) aliphatic -( c6 - c10 ) aryl , wherein each of r 2 and r 4 is independently and optionally substituted with up to 3 substituents independently selected from j ; wherein up to two aliphatic carbon atoms in r 2 and r 4 may be replaced by a heteroatom selected from o , nh , s , so , and so 2 ; r 5 is —( c1 - c12 ) aliphatic , wherein any hydrogen is optionally replaced with halogen , and wherein any hydrogen or halogen atom bound to any terminal carbon atom of r 5 is optionally substituted with sulfhydryl or hydroxy ; hydrogen , —( c1 - c12 ) aliphatic , —( c6 - c10 ) aryl , —( c6 - c10 ) aryl -( c1 - c12 ) aliphatic , —( c3 - c10 )- cycloalkyl or - cycloalkenyl , —( c1 - c12 )- aliphatic -[( c3 - c10 )- cycloalkyl or - cycloalkenyl ], —( c3 - c10 ) heterocyclyl , —( c3 - c10 ) heterocyclyl -( c1 - c12 ) aliphatic , —( c5 - c10 ) heteroaryl , or —( c1 - c12 ) aliphatic -( c5 - c10 ) heteroaryl , or two r 6 groups , which are bound to the same nitrogen atom , form together with that nitrogen atom , a —( c3 - c10 ) heterocyclic ring ; wherein r 6 is optionally substituted with up to 3 j substituents or with a suitable electron withdrawing group ; v is — c ( o ) n ( r 8 )—, — s ( o ) n ( r 8 )—, — s ( o ) 2 n ( r 8 )—, a bond , — ch ( r 8 )—, — n ( r 8 )—, — o —, — o — ch ( r 8 )—, — s —, — s — ch ( r 8 ), — c ( o )—, — c ( o )— o —, — c ( o )— s —, — c ( o )— chr 8 —, — s ( o )—, — s ( o )— ch ( r 8 ), — s ( o )— n ( r 8 )— chr 8 , — s ( o ) 2 —, — s —( o ) 2 — ch ( r 8 )—, or — s ( o ) 2 — n ( r 8 )— chr 8 ; —( c6 - c10 ) aryl , —( c1 - c12 ) aliphatic -( c6 - c10 ) aryl , —( c3 - c10 )- cycloalkyl or - cycloalkenyl , —( c1 - c12 ) aliphatic -[( c3 - c10 )- cycloalkyl or - cycloalkenyl ], —( c3 - c10 ) heterocyclyl , —( c1 - c12 ) aliphatic -( c3 - c10 ) heterocyclyl , —( c5 - c10 ) heteroaryl , or —( c1 - c12 ) aliphatic -( c5 - c10 ) heteroaryl ; or hydrogen , —( c1 - c12 ) aliphatic , —( c6 - c10 ) aryl , —( c1 - c12 ) aliphatic -( c6 - c10 ) aryl , —( c3 - c10 )- cycloalkyl or - cycloalkenyl , —( c1 - c12 ) aliphatic -[( c3 - c10 )- cycloalkyl or - cycloalkenyl ], —( c3 - c10 ) heterocyclyl , —( c1 - c12 ) aliphatic -( c3 - c10 ) heterocyclyl , —( c5 - c10 ) heteroaryl , or —( c1 - c12 ) aliphatic -( c5 - c10 ) heteroaryl , wherein each t is optionally substituted with up to 3 j substituents ; k is a bond , —( c1 - c12 ) aliphatic , — o —, — s —, — nr 9 —, — c ( o )—, or — c ( o )— nr 9 —, wherein r 9 is hydrogen or —( c1 - c12 ) aliphatic ; each r 20 is independently hydrogen , —( c1 - c6 ) aliphatic or — o —(( c1 - c6 ) aliphatic ); or each r 20 is taken together with the carbon atoms to which they are bound to form a ( c3 - c6 ) cycloalkyl . the term “ aryl ” as used herein means a monocyclic or bicyclic carbocyclic aromatic ring system . phenyl is an example of a monocyclic aromatic ring system . bicyclic aromatic ring systems include systems wherein both rings are aromatic , e . g ., naphthyl , and systems wherein only one of the two rings is aromatic , e . g ., tetralin . the bond “ - - - ” refers to an optionally present bond . the term “ heterocyclyl ” as used herein means a monocyclic or bicyclic non - aromatic ring system having up to 4 , and preferably 1 to 3 , heteroatom or heteroatom groups in each ring selected from o , n , nh , s , so , or so 2 in a chemically stable arrangement . in a bicyclic non - aromatic ring system embodiment of “ heterocyclyl ” one or both rings may contain said heteroatom or heteroatom groups . heterocyclic rings include 3 - 1h - benzimidazol - 2 - one , 3 -( 1 - alkyl )- benzimidazol - 2 - one , 2 - tetrahydrofuranyl , 3 - tetrahydrofuranyl , 2 - tetrahydrothiophenyl , 3 - tetrahydrothiophenyl , 2 - morpholino , 3 - morpholino , 4 - morpholino , 2 - thiomorpholino , 3 - thiomorpholino , 4 - thiomorpholino , 1 - pyrrolidinyl , 2 - pyrrolidinyl , 3 - pyrrolidinyl , 1 - tetrahydropiperazinyl , 2 - tetrahydropiperazinyl , 3 - tetrahydropiperazinyl , 1 - piperidinyl , 2 - piperidinyl , 3 - piperidinyl , 1 - pyrazolinyl , 3 - pyrazolinyl , 4 - pyrazolinyl , 5 - pyrazolinyl , 1 - piperidinyl , 2 - piperidinyl , 3 - piperidinyl , 4 - piperidinyl , 2 - thiazolidinyl , 3 - thiazolidinyl , 4 - thiazolidinyl , 1 - imidazolidinyl , 2 - imidazolidinyl , 4 - imidazolidinyl , 5 - imidazolidinyl , indolinyl , tetrahydroquinolinyl , tetrahydroisoquinolinyl , benzothiolane , and benzodithiane . the term “ heteroaryl ” as used herein means a monocyclic or bicyclic aromatic ring system having up to 4 , and preferably 1 to 3 , heteroatom or heteroatom groups in each ring selected from o , n , nh or s in a chemically stable arrangement . in such a bicyclic aromatic ring system embodiment of “ heteroaryl ”: one or both rings may be aromatic ; and one or both rings may contain said heteroatom or heteroatom groups . heteroaryl rings include 2 - furanyl , 3 - furanyl , n - imidazolyl , 2 - imidazolyl , 4 - imidazolyl , 5 - imidazolyl , benzimidazolyl , 3 - isoxazolyl , 4 - isoxazolyl , 5 - isoxazolyl , 2 - oxazolyl , 4 - oxazolyl , 5 - oxazolyl , n - pyrrolyl , 2 - pyrrolyl , 3 - pyrrolyl , 2 - pyridyl , 3 - pyridyl , 4 - pyridyl , 2 - pyrimidinyl , 4 - pyrimidinyl , 5 - pyrimidinyl , pyridazinyl ( e . g ., 3 - pyridazinyl ), 2 - thiazolyl , 4 - thiazolyl , 5 - thiazolyl , tetrazolyl ( e . g ., 5 - tetrazolyl ), triazolyl ( e . g ., 2 - triazolyl and 5 - triazolyl ), 2 - thienyl , 3 - thienyl , benzofuryl , benzothiophenyl , indolyl ( e . g ., 2 - indolyl ), pyrazolyl ( e . g ., 2 - pyrazolyl ), isothiazolyl , 1 , 2 , 3 - oxadiazolyl , 1 , 2 , 5 - oxadiazolyl , 1 , 2 , 4 - oxadiazolyl , 1 , 2 , 3 - triazolyl , 1 , 2 , 3 - thiadiazolyl , 1 , 3 , 4 - thiadiazolyl , 1 , 2 , 5 - thiadiazolyl , purinyl , pyrazinyl , 1 , 3 , 5 - triazinyl , quinolinyl ( e . g ., 2 - quinolinyl , 3 - quinolinyl , 4 - quinolinyl ), and isoquinolinyl ( e . g ., 1 - isoquinolinyl , 3 - isoquinolinyl , or 4 - isoquinolinyl ). each of the above aryl , heterocyclyl or heteroaryl above may contain up to 3 substituents independently selected from halogen , — or ′, — no 2 , — cf 3 , — ocf 3 , — r ′, oxo , — or ′, — o - benzyl , — o - phenyl , 1 , 2 - methylenedioxy , — n ( r ′) 2 , — c ( o ) r ′, — coor ′ or — con ( r ′) 2 , wherein r ′ is independently selected from h , ( c1 - c6 )— alkyl , ( c2 - c6 )- alkenyl or alkynyl . the term “ aliphatic ” as used herein means a straight chained or branched alkyl , alkenyl or alkynyl . it is understood that alkenyl or alkynyl embodiments need at least two carbon atoms in the aliphatic chain . the term “ cycloalkyl or cycloalkenyl ”, refers to a monocyclic or fused or bridged bicyclic carbocyclic ring system that is not aromatic . cycloalkenyl rings have one or more units of unsaturation . preferred cycloalkyl groups include cyclopropyl , cyclobutyl , cyclopentyl , cyclohexyl , cyclohexenyl , cycloheptyl , cycloheptenyl , nornbornyl , adamantyl and decalin - yl . the phrase “ chemically stable arrangement ” as used herein refers to a compound structure that renders the compound sufficiently stable to allow manufacture and administration to a mammal by methods known in the art . typically , such compounds are stable at a temperature of 40 ° c . or less , in the absence of moisture or other chemically reactive condition , for at least a week . according to a preferred embodiment , ring a together with x and the atoms to which x is bound , has up to 3 heteroatoms independently selected from n , nh , o , so , and so 2 . according to a preferred embodiment , ring a together with x and the atoms to which x is bound , is a 3 - 6 membered carbocyclic non - aromatic or aromatic ring . more preferably , ring a , together with x and the atoms to which x is bound , is cyclopropyl , cyclobutyl , cyclopentyl , cyclohexyl or phenyl . even more preferably , ring a , together with x and the atoms to which x is bound , is cylcohexyl or cyclopentyl . most preferably , ring a , together with x and the atoms to which x is bound , is cyclohexyl . according to another preferred embodiment , ring a , together with x and the atoms to which x is bound , is a 3 - 6 membered heterocyclic ring . more preferably , ring a together with x and the atoms to which x is bound , is a 5 - 6 membered heterocyclic ring . according to another preferred embodiment , ring a together with x and the atoms to which x is bound , is a 5 - 6 membered heteroaryl ring . according to yet another preferred embodiment , ring a , together with x and the atoms to which x is bound , is fused to a ( c6 - c10 ) aryl , ( c5 - c10 ) heteroaryl , ( c3 - c10 ) cycloalkyl or ( c3 - c10 )— heterocyclyl . preferably , ring a together with x and the atoms to which x is bound , is fused to cyclohexyl , cyclopentyl , phenyl or pyridyl . according to a preferred embodiment , compounds of the present invention have formula ( ia ): wherein t , v , r 1 , r 2 , r 3 , r 4 , r 5 , r 20 , x , w , and m are as defined herein . according to another preferred embodiment , compounds of the present invention have formula ( ib ): wherein t , v , r 1 , r 3 , r 5 , r 20 , x , w and m are as defined herein . according to another preferred embodiment , r 5 is c2 - c3 alkyl substituted with 1 - 3 chlorine or fluorine . according to yet another preferred embodiment t or r 6 is a heterocyclyl or heteroaryl , optionally having up to 3 substituents as defined above . according to yet another preferred embodiment , t is selected from 3 - 1h - benzimidazol - 2 - one , 3 -( 1 - alkyl )- benzimidazol - 2 - one , 2 - tetrahydrofuranyl , 3 - tetrahydrofuranyl , pyrazolinyl , 1 , 3 - dihydro - imidazol - 2 - one , 2 - imidazolyl , 4 - imidazolyl , 5 - imidazolyl , 2 - oxazolyl , 4 - oxazolyl , 5 - oxazolyl , 2 - pyrrolyl , 3 - pyrrolyl , 2 - pyrimidinyl , 4 - pyrimidinyl , 5 - pyrimidinyl , 5 - tetrazolyl , pyrazolyl , pyrazinyl or 1 , 3 , 5 - triazinyl . even more preferably , t or r 7 is 3 - 1h - benzimidazol - 2 - one , 3 -( 1 - alkyl )- benzimidazol - 2 - one , 2 - pyrazolinyl , 1 , 3 - dihydro - imidazol - 2 - one , 2 - imidazolyl , 2 - pyrrolyl , 2 - pyrimidinyl , 5 - pyrimidinyl , 5 - tetrazolyl or pyrazinyl . most preferred is when t or r 7 is selected from : preferred substituents on t or r 7 in the above embodiments are halogen , — cf 3 , — ocf 3 , oxo , — coor ′ or — con ( r ′) 2 , wherein r ′ is as defined above . in another preferred embodiment of the present invention , r 1 is — ch 2 — ch ( ch 3 )— ch 3 , — c ( ch 3 ) 3 , — ch ( ch 3 ) 2 , — ch ( ch 3 )— ch 2 — ch 3 or cyclohexyl . most preferably r 1 is cyclohexyl . according to another preferred embodiment , r 3 is selected from — c ( ch 3 ) 2 , — ch ( ch 3 ) 2 , — ch ( ch 3 )— ch 2 — ch 3 or cyclohexyl . more preferably , r 3 is selected from — c ( ch 3 ) 3 , or — ch ( ch 3 ) 2 . according to yet another preferred embodiment , each r 2 is independently selected from — ch 3 or hydrogen . even more preferred is when r 2 is hydrogen . according to another preferred embodiment , r 5 is — ch 2 ch 2 ch 3 , — ch 2 ch 2 ch 2 ch 3 , — ch 2 ch 2 ch 2 f , — ch 2 ch 2 chf 2 , or — ch 2 ch 2 cf 3 . more preferred is when r 5 is — ch 2 ch 2 ch 2 ch 3 or — ch 2 ch 2 chf 2 . most preferably r 5 is — ch 2 ch 2 ch 2 ch 3 . according to another preferred embodiment , r 5 is — ch 2 ch 3 , — ch 2 ch 2 ch 3 , — ch 2 ch 2 f , — ch 2 chf 2 , or — ch 2 cf 3 . most preferred is when r 5 is — ch 2 ch 2 ch 3 , or — ch 2 chf 2 . most preferably r 5 is — ch 2 ch 2 ch 3 . according to a preferred embodiment , w is — c ( o )— c ( o )— r 6 . preferably , r 6 is isopropyl . according to another preferred embodiment , w is — c ( o )— c ( o )— or 6 . preferably , r 6 is hydrogen , ( c1 - c12 )- aliphatic , ( c6 - c10 )- aryl , ( c3 - c10 )- cycloalkyl or - cycloalkenyl , ( c3 - c10 )- heterocyclyl or ( c 5 - c 10 ) heteroaryl . more preferably , r 6 is h or methyl . according to another preferred embodiment , w is — c ( o )— c ( o )— n ( r 6 ) 2 . preferably , r 6 is hydrogen , ( c3 - c10 )- cycloalkyl or - cycloalkenyl , or ( c3 - c10 )- heterocyclyl . in another preferred embodiment of formula i is where w is c ( o )— c ( o )— n ( r 6 ) 2 , the nr 6 r 6 portion of the w moiety is — nh — ( c3 - c6 ) cycloalkyl , — nh — ch ( ch 3 )—( c6 - c10 ) aryl or — nh — ch ( ch 3 )—( c3 - c10 ) heterocyclyl , or — nh — ch ( ch 3 )—( c 5 - c 10 ) heteroaryl , wherein said aryl , heterocyclyl , or heteroaryl is optionally substituted with halogen . alternatively , the nr 6 r 6 portion is — nh —( c 3 - c 6 ) cycloalkyl , — nh — ch ( ch 3 )—( c6 - c10 ) aryl , or — nh — ch ( ch 3 )—( c5 - c10 ) heteroaryl , wherein said aryl or said heterocyclyl is optionally substituted with halogen ; or nr 6 r 6 is — nh —( c3 - c6 ) cycloalkyl , — nh — ch ( ch 3 )—( c6 - c10 ) aryl , or — nh — ch ( ch 3 )—( c3 - c10 ) heterocyclyl , wherein said aryl or said heterocyclyl is optionally substituted with halogen . in other preferred embodiment of formula i , nr 6 r 6 in w is : in a preferred embodiment of the present invention , x is —[ ch 2 ] o —, —[ cj ′ j ′] o —, —[ ch 2 ] m — o —, —[ ch 2 ] m — s ( o ) 2 —, —[ ch 2 ] m — so —, —[ cr 20 r 20 ] m — nr 21 —, or —[ cr 20 r 20 ] m — nj ″—. in a more preferred embodiment of the present invention , x is — cr 20 r 20 —; — o —; — s ( o ) 2 ; or nr 21 . preferred embodiments of r 20 are selected from hydrogen , — c 1 - c 6 - aliphatic and — o —( c 1 - c 6 - aliphatic ); or each r 20 is taken together with the carbon atoms to which they are bound to form a ( c3 - c6 ) cycloalkyl . preferably , these aliphatic groups are alkyl groups . preferred embodiments of r 21 are selected from hydrogen and — c ( o )— o — r 22 . in yet another preferred embodiment , x is — ch 2 —, — o —, — so 2 — or — nr 21 —, wherein r 21 is hydrogen . even more preferred is when the bridged bicyclic moiety is fully saturated . according to another preferred embodiment of this invention , t contains at least one hydrogen bond donor moiety selected from — nh 2 , — nh —, — oh , and — sh . t is optionally substituted with up to 3 j substituents , wherein j is as defined in claim 1 ; z is independently o , s , nr 10 , or c ( r 10 ) 2 ; ( c6 - c10 )- aryl , ( c6 - c10 )- aryl -( c1 - c12 ) aliphatic , ( c3 - c10 )- cycloalkyl or - cycloalkenyl , [( c3 - c10 )- cycloalkyl or - cycloalkenyl ]-( c1 - c12 )- aliphatic , ( c3 - c10 )- heterocyclyl , ( c3 - c10 )- heterocyclyl -( c1 - c12 )- aliphatic , ( c5 - c10 ) heteroaryl , or ( c5 - c10 ) heteroaryl -( c1 - c12 )- aliphatic , wherein each t is optionally substituted with up to 3 j substituents . r 10 is : hydrogen , ( c1 - c12 )- aliphatic , ( c6 - c10 )- aryl , ( c6 - c10 )- aryl -( c1 - c12 ) aliphatic , ( c3 - c10 )- cycloalkyl or - cycloalkenyl , [( c3 - c10 )- cycloalkyl or - cycloalkenyl ]-( c 1 - c12 )- aliphatic , ( c3 - c10 )- heterocyclyl , ( c3 - c10 )- heterocyclyl -( c1 - c12 )- aliphatic , ( c5 - c10 ) heteroaryl , or ( c5 - c10 ) heteroaryl -( c1 - c12 )- aliphatic , wherein each t is optionally substituted with up to 3 j substituents ; k is a bond , — o —, — s —, — nr 9 —, — c ( o )—, or — c ( o )— nr 9 —, in yet another preferred embodiment , r 2 and r 4 are each independently h , methyl , ethyl , or propyl . according to a preferred embodiment , v is — c ( o )— nr 8 —. more preferably , v is — c ( o )— nh —. more preferably , the compound of this invention has the structure and stereochemistry depicted below in formula ii : wherein r 3 and r 6 represent the most preferred embodiments set forth above . any of the preferred embodiments recited above may be combined to produce a preferred embodiment of this invention . the compounds of this invention may be synthesized by standard chemical schemes well - known in the art . such schemes are set forth below , but other equivalent schemes , which will be readily apparent to the ordinary skilled organic chemist , may alternatively be used to synthesize various portions of the molecule . for example , compounds of formula i , wherein w is c ( o ) oh or c ( o ) c ( o )) r 6 may be prepared according to the methods depicted in schemes 11 and / or 12 . more specific synthesis schemes for individual compounds within applicants &# 39 ; invention are set forth in the examples . as set forth above , the compounds of this invention are capable of inhibiting the activity of hcv ns3 - ns4a protease . in order to quantitate the activity of the compounds of this invention , cells containing hcv replicon were incubated with the compounds of this invention , and a taqman real time pcr assay was conducted to determine the percentage inhibition of hcv rna level and the ic50 were calculated therefrom . the result are shown below in table 1 : another embodiment of this invention provides a composition comprising a compound of formula i or a pharmaceutically acceptable salt thereof in an amount effective to decrease the viral load in a sample or in a patient , wherein said virus encodes a serine protease necessary for the viral life cycle , and a pharmaceutically acceptable carrier . if pharmaceutically acceptable salts of the compounds of this invention are utilized in these compositions , those salts are preferably derived from inorganic or organic acids and bases . included among such acid salts are the following : acetate , adipate , alginate , aspartate , benzoate , benzene sulfonate , bisulfate , butyrate , citrate , camphorate , camphor sulfonate , cyclopentane - propionate , digluconate , dodecylsulfate , ethanesulfonate , fumarate , glucoheptanoate , glycerophosphate , hemisulfate , heptanoate , hexanoate , hydrochloride , hydrobromide , hydroiodide , 2 - hydroxyethanesulfonate , lactate , maleate , methanesulfonate , 2 - naphthalenesulfonate , nicotinate , oxalate , pamoate , pectinate , persulfate , 3 - phenyl - propionate , picrate , pivalate , propionate , succinate , tartrate , thiocyanate , tosylate and undecanoate . base salts include ammonium salts , alkali metal salts , such as sodium and potassium salts , alkaline earth metal salts , such as calcium and magnesium salts , salts with organic bases , such as dicyclohexylamine salts , n - methyl - d - glucamine , and salts with amino acids such as arginine , lysine , and so forth . also , the basic nitrogen - containing groups may be quaternized with such agents as lower alkyl halides , such as methyl , ethyl , propyl , and butyl chloride , bromides and iodides ; dialkyl sulfates , such as dimethyl , diethyl , dibutyl and diamyl sulfates , long chain halides such as decyl , lauryl , myristyl and stearyl chlorides , bromides and iodides , aralkyl halides , such as benzyl and phenethyl bromides and others . water or oil - soluble or dispersible products are thereby obtained . the compounds utilized in the compositions and methods of this invention may also be modified by appending appropriate functionalities to enhance selective biological properties . such modifications are known in the art and include those which increase biological penetration into a given biological system ( e . g ., blood , lymphatic system , central nervous system ), increase oral availability , increase solubility to allow administration by injection , alter metabolism and alter rate of excretion . pharmaceutically acceptable carriers that may be used in these compositions include , but are not limited to , ion exchangers , alumina , aluminum stearate , lecithin , serum proteins , such as human serum albumin , buffer substances such as phosphates , glycine , sorbic acid , potassium sorbate , partial glyceride mixtures of saturated vegetable fatty acids , water , salts or electrolytes , such as protamine sulfate , disodium hydrogen phosphate , potassium hydrogen phosphate , sodium chloride , zinc salts , colloidal silica , magnesium trisilicate , polyvinyl pyrrolidone , cellulose - based substances , polyethylene glycol , sodium carboxymethylcellulose , polyacrylates , waxes , polyethylene - polyoxypropylene - block polymers , polyethylene glycol and wool fat . according to a preferred embodiment , the compositions of this invention are formulated for pharmaceutical administration to a mammal , preferably a human being . such pharmaceutical compositions of the present invention may be administered orally , parenterally , by inhalation spray , topically , rectally , nasally , buccally , vaginally or via an implanted reservoir . the term “ parenteral ” as used herein includes subcutaneous , intravenous , intramuscular , intra - articular , intra - synovial , intrasternal , intrathecal , intrahepatic , intralesional and intracranial injection or infusion techniques . preferably , the compositions are administered orally or intravenously . sterile injectable forms of the compositions of this invention may be aqueous or oleaginous suspension . these suspensions may be formulated according to techniques known in the art using suitable dispersing or wetting agents and suspending agents . the sterile injectable preparation may also be a sterile injectable solution or suspension in a non - toxic parenterally acceptable diluent or solvent , for example as a solution in 1 , 3 - butanediol . among the acceptable vehicles and solvents that may be employed are water , ringer &# 39 ; s solution and isotonic sodium chloride solution . in addition , sterile , fixed oils are conventionally employed as a solvent or suspending medium . for this purpose , any bland fixed oil may be employed including synthetic mono - or di - glycerides . fatty acids , such as oleic acid and its glyceride derivatives are useful in the preparation of injectables , as are natural pharmaceutically - acceptable oils , such as olive oil or castor oil , especially in their polyoxyethylated versions . these oil solutions or suspensions may also contain a long - chain alcohol diluent or dispersant , such as carboxymethyl cellulose or similar dispersing agents which are commonly used in the formulation of pharmaceutically acceptable dosage forms including emulsions and suspensions . other commonly used surfactants , such as tweens , spans and other emulsifying agents or bioavailability enhancers which are commonly used in the manufacture of pharmaceutically acceptable solid , liquid , or other dosage forms may also be used for the purposes of formulation . the pharmaceutical compositions of this invention may be orally administered in any orally acceptable dosage form including , but not limited to , capsules , tablets , aqueous suspensions or solutions . in the case of tablets for oral use , carriers that are commonly used include lactose and corn starch . lubricating agents , such as magnesium stearate , are also typically added . for oral administration in a capsule form , useful diluents include lactose and dried cornstarch . when aqueous suspensions are required for oral use , the active ingredient is combined with emulsifying and suspending agents . if desired , certain sweetening , flavoring or coloring agents may also be added . alternatively , the pharmaceutical compositions of this invention may be administered in the form of suppositories for rectal administration . these may be prepared by mixing the agent with a suitable non - irritating excipient which is solid at room temperature but liquid at rectal temperature and therefore will melt in the rectum to release the drug . such materials include cocoa butter , beeswax and polyethylene glycols . the pharmaceutical compositions of this invention may also be administered topically , especially when the target of treatment includes areas or organs readily accessible by topical application , including diseases of the eye , the skin , or the lower intestinal tract . suitable topical formulations are readily prepared for each of these areas or organs . topical application for the lower intestinal tract may be effected in a rectal suppository formulation ( see above ) or in a suitable enema formulation . topically - transdermal patches may also be used . for topical applications , the pharmaceutical compositions may be formulated in a suitable ointment containing the active component suspended or dissolved in one or more carriers . carriers for topical administration of the compounds of this invention include , but are not limited to , mineral oil , liquid petrolatum , white petrolatum , propylene glycol , polyoxyethylene , polyoxypropylene compound , emulsifying wax and water . alternatively , the pharmaceutical compositions may be formulated in a suitable lotion or cream containing the active components suspended or dissolved in one or more pharmaceutically acceptable carriers . suitable carriers include , but are not limited to , mineral oil , sorbitan monostearate , polysorbate 60 , cetyl esters wax , cetearyl alcohol , 2 - octyldodecanol , benzyl alcohol and water . for ophthalmic use , the pharmaceutical compositions may be formulated as micronized suspensions in isotonic , ph adjusted sterile saline , or , preferably , as solutions in isotonic , ph adjusted sterile saline , either with our without a preservative such as benzylalkonium chloride . alternatively , for ophthalmic uses , the pharmaceutical compositions may be formulated in an ointment such as petrolatum . the pharmaceutical compositions of this invention may also be administered by nasal aerosol or inhalation . such compositions are prepared according to techniques well known in the art of pharmaceutical formulation and may be prepared as solutions in saline , employing benzyl alcohol or other suitable preservatives , absorption promoters to enhance bioavailability , fluorocarbons , and / or other conventional solubilizing or dispersing agents . in a related embodiment , the compositions of this invention additionally comprise another anti - viral agent , preferably an anti - hcv agent . such anti - viral agents include , but are not limited to , immunomodulatory agents , such as α -, β -, and γ - interferons and pegylated derivatized interferon - α compounds ; other anti - viral agents , such as ribavirin and amantadine ; other inhibitors of hepatitis c proteases ( ns2 - ns3 inhibitors and ns3 - ns4a inhibitors ); inhibitors of other targets in the hcv life cycle , including helicase and polymerase inhibitors ; inhibitors of internal ribosome entry ; broad - spectrum viral inhibitors , such as impdh inhibitors ( e . g ., vx - 497 and other impdh inhibitors disclosed in u . s . pat . no . 5 , 807 , 876 , mycophenolic acid and derivatives thereof ); or combinations of any of the above . upon improvement of a patient &# 39 ; s condition , a maintenance dose of a compound , composition or combination of this invention may be administered , if necessary . subsequently , the dosage or frequency of administration , or both , may be reduced , as a function of the symptoms , to a level at which the improved condition is retained when the symptoms have been alleviated to the desired level , treatment should cease . patients may , however , require intermittent treatment on a long - term basis upon any recurrence of disease symptoms . it should also be understood that a specific dosage and treatment regimen for any particular patient will depend upon a variety of factors , including the activity of the specific compound employed , the age , body weight , general health , sex , diet , time of administration , rate of excretion , drug combination , and the judgment of the treating physician and the severity of the particular disease being treated . the amount of active ingredients will also depend upon the particular described compound and the presence or absence and the nature of the additional anti - viral agent in the composition . according to another embodiment , the invention provides a method for treating a patient infected with a virus characterized by a virally encoded serine protease that is necessary for the life cycle of the virus by administering to said patient a pharmaceutically acceptable composition of this invention . preferably , the methods of this invention are used to treat a patient suffering from a hcv infection . such treatment may completely eradicate the viral infection or reduce the severity thereof . more preferably , the patient is a human being . in an alternate embodiment , the methods of this invention additionally comprise the step of administering to said patient an anti - viral agent preferably an anti - hcv agent . such anti - viral agents include , but are not limited to , immunomodulatory agents , such as α -, β -, and γ - interferons and pegylated derivatized interferon - α compounds ; other anti - viral agents , such as ribavirin and amantadine ; other inhibitors of hepatitis c proteases ( ns2 - ns3 inhibitors and ns3 - ns4a inhibitors ); inhibitors of other targets in the hcv life cycle , including helicase and polymerase inhibitors ; inhibitors of internal ribosome entry ; broad - spectrum viral inhibitors , such as impdh inhibitors ( e . g ., vx - 497 and other impdh inhibitors disclosed in u . s . pat . no . 5 , 807 , 876 , mycophenolic acid and derivatives thereof ); or combinations of any of the above . such additional agent may be administered to said patient as part of a single dosage form comprising both a compound of this invention and an additional anti - viral agent . alternatively the additional agent may be administered separately from the compound of this invention , as part of a multiple dosage form , wherein said additional agent is administered prior to , together with or following a composition comprising a compound of this invention . in yet another embodiment the present invention provides a method of pre - treating a biological substance intended for administration to a patient comprising the step of contacting said biological substance with a pharmaceutically acceptable composition comprising a compound of this invention . such biological substances include , but are not limited to , blood and components thereof such as plasma , platelets , subpopulations of blood cells and the like ; organs such as kidney , liver , heart , lung , etc ; sperm and ova ; bone marrow and components thereof , and other fluids to be infused into a patient such as saline , dextrose , etc . according to another embodiment the invention provides methods of treating materials that may potentially come into contact with a virus characterized by a virally encoded serine protease necessary for its life cycle . this method comprises the step of contacting said material with a compound according to the invention . such materials include , but are not limited to , surgical instruments and garments ; laboratory instruments and garments ; blood collection apparatuses and materials ; and invasive devices , such as shunts , stents , etc . in another embodiment , the compounds of this invention may be used as laboratory tools to aid in the isolation of a virally encoded serine protease . this method comprises the steps of providing a compound of this invention attached to a solid support ; contacting said solid support with a sample containing a viral serine protease under conditions that cause said protease to bind to said solid support ; and eluting said serine protease from said solid support . preferably , the viral serine protease isolated by this method is hcv ns3 - ns4a protease . in order that this invention be more fully understood , the following examples are set forth . these examples are for the purpose of illustration only and are not to be construed as limiting the scope of the invention in any way . ethyl ( 1s , 3s , 4r )- 2 -[( 1r )- 1 - phenylethyl ]- 2 - azabicyclo [ 2 . 2 . 1 ] hept - 5 - ene - 3 - carboxylate ( 1 ) ( example for n = o , m = 0 ; each r 20 = h ) see scheme 1 ( r )- methylbenzylamine ( 15 ml ; 0 . 118 mol ; 1 . 05 eq ) was added to a stirred 0 ° c . solution of for example , ethyl glyoxylate 50 % in toluene ( 23 ml ; 0 . 112 mol ; 1 . 0 eq ) in 600 ml of anhydrous dcm containing 27 g of 4a molecular sieve . the reaction mixture was stirred at 0 ° c . for 1 h . then it was lowered to − 78 ° c . the 3 following reagents were sequentially added with 5 min . in between each addition : tfa ( 9 . 08 ml ; 0 . 118 mmol ; 1 . 05 eq ), boron trifluoride etherate ( 14 . 93 ml ; 0 . 118 mol ; 1 . 05 eq ) and , for example , cyclopentadiene ( 16 . 37 ml ; 0 . 146 mol ; 1 . 3 eq ). the reaction mixture was stirred at − 78 ° c . for 5 h before it was allowed to warm to rt . the molecular sieves were separated and the reaction mixture was carefully washed with saturated aqueous sodium hydrogen carbonate ( 250 ml ), brine ( 250 ml ), and dried with magnesium sulfate . concentration and purification by flash chromatography ( hexanes : etoac : tea ( 89 : 10 : 1 ) afforded ( in order of elution ) 2 . 3 g ( 7 .%) of minor endo - isomer and 23 . 5 g ( 78 %) of the major exo - isomer 1 . the compound was characterized using nmr . the aza diels - alder adduct 1 ( 23 . 5 g ; 0 . 086 mol ) was dissolved in 200 ml of absolute ethanol , and , for example , pd - c 10 % ( 600 mg ) was added . the mixture was stirred at rt under hydrogen ( 55 psi ) for 16 h . filtration through a pad of celite ( or nylon / carbon filter combination ) and concentration yielded 14 . 2 g of 2 ( 97 %) as a pale yellow oil which was used directly for the next step . the compound was characterized using nmr . ( 1s , 3s , 4r )- 2 - benzoylazabicyclo [ 2 . 2 . 1 ] heptane - 3 - carboxylic acid 3 ( example for o = 1 , m = 0 , each r 20 = h ) amino ester 2 ( 3 . 45 g ; 0 . 0204 mol ; 1 . 0 eq ) was added a mixture of , for example , 1n naoh ( 71 ml ; 0 . 143 mol ; 3 . 5 eq ) and 71 ml of water and stirred at rt for 4 h ( tlc monitoring w / mixture of etoac and 5 % tea ). when the saponification is complete , 100 ml of acetone was added and the temperature was lowered to 0 ° c . benzyl chloroformate ( 3 . 5 ml ; 0 . 0244 mol ; 1 . 2 eq ) in 40 ml of acetone was slowly added and the reaction mixture was allowed to stir at rt for 16 h with maintaining the ph to roughly 9 to 10 with 1n naoh . the acetone was removed and 200 ml of water was added . the aqueous phase was washed with ether ( 3 × 200 ml ) and the aqueous phase acidified to ph 2 - 3 with 2n hcl . extraction of the product with ( 3 × 250 ml ) of etoac , drying ( na 2 so 4 ) and concentration in vacuo provided 3 . 85 g ( 70 %) of amino acid 3 . the compound was used directly for the next step . the compound was characterized using nmr . in a sealed tube , 140 μl of concentrated sulfuric acid was added to a solution of acid 3 ( 3 . 86 g ; 0 . 014 mol ) in 30 ml of dcm . the solution was brought to − 20 ° c . and saturated with isobutylene , causing a volume increase of 14 ml . after 70 h at rt , the cap was remove to release the pressure and the solution was added to 25 ml of water containing sodium carbonate sufficient to neutralize all acid . the compound 4 was used directly for the next step without further purification . the compound was characterized using nmr . removal of the cbz group with hydrogenation under 1 atm of hydrogen using pd - c10 % in ethanol gave , after 5 h , the desired aminoester intermediate in quantitative yield . the crude compound was coupled to tert - butylglycine shown in the next step . tert - butyl glycine coupling to product 5 ( example for 0 = 1 , m = 0 , each r 20 = h , r 3 = t - bu ) to a solution of cbz - tert - butyl glycine ( 3 . 33 g ; 0 . 0126 mol ; 1 . 0 eq ) in 20 ml of dcm at 0 ° c . was added , for example , edc ( 2 . 89 g ; 0 . 015 mol ; 1 . 2 eq ), hobt ( 2 . 5 g ; 0 . 0163 mol ; 1 . 3 eq ) and diea ( 6 . 57 ml ; 0 . 038 mol ; 3 . 0 eq ). the resulting mixture was stirred at 0 ° c . for 15 min . after which , the above amino ester was slowly added in 10 ml of dcm . the resulting reaction mixture was stirred at rt for 16 h . concentrated to a residue that was redissolved in etoac . successive washes with 0 . 5n hcl , satd ′ aqueous nahco 3 and brine gave after drying ( na 2 so 4 ) and concentration in vacuo the desired product which was subjected to flash chromatography ( 20 % etoac / 80 % hexanes ) to provide pure 5 . the compound was characterized using nmr . the rest of the synthesis was done using standard amino acid coupling which were reported in previous patent . ethyl ( 1s , 3s , 4r )- 2 -[( 1r )- 1 - phenylethyl ]- 2 - azabicyclo [ 2 . 2 . 2 ] oct - 5 - ene - 3 - carboxylate ( 1 ) ( example for o = 1 , m = 0 ; each r 20 = h ) see scheme 2 the preparation of the azabicyclo [ 2 . 2 . 2 ] oct - 5 - ene was achieved using the same experimental as above with the procedural change that 1 , 3 - cyclohexadiene was used instead of cyclopentadiene . the rest of the synthesis was done using standard amino acid coupling which have been reported . cells containing hepatitis c virus ( hcv ) replicon were maintained in dmem containing 10 % fetal bovine serum ( fbs ), 0 . 25 mg per ml of g418 , with appropriate supplements ( media a ). on day 1 , replicon cell monolayer was treated with a trypsin : edta mixture , removed , and then dilutedh media a into a final concentration of 100 , 000 cells per ml wit . 10 , 000 cells in 100 ul are plated into each well of a 96 - well tissue culture plate , and culture overnight in a tissue culture incubator at 37 ° c . on day 2 , compounds ( in 100 % dmso ) were serially diluted into dmem containing 2 % fbs , 0 . 5 % dmso , with appropriate supplements ( media b ). the final concentration of dmso was maintained at 0 . 5 % throughout the dilution series . the media on the replicon cell monolayer was removed , and then media b containing various concentrations of compounds was added . media b without any compound was added to other wells as no compound controls . cells were incubated with compound or 0 . 5 % dmso in media b for 48 hours in a tissue culture incubator at 37 ° c . at the end of the 48 - hour incubation , the media was removed , and the replicon cell monolayer was washed once with pbs and stored at − 80 ° c . prior to rna extraction . culture plates with treated replicon cell monolayers were thawed , and a fixed amount of another rna virus , such as bovine viral diarrhea virus ( bvdv ) was added to cells in each well . rna extraction reagents ( such as reagents from rneasy kits ) were added to the cells immediately to avoid degradation of rna . total rna was extracted according the instruction of manufacturer with modification to improve extraction efficiency and consistency . finally , total cellular rna , including hcv replicon rna , was eluted and stored at − 80 ° c . until further processing . a taqman real - time rt - pcr quantification assay was set up with two sets of specific primers and probe . one was for hcv and the other was for bvdv . total rna extractants from treated hcv replicon cells were added to the pcr reactions for quantification of both hcv and bvdv rna in the same pcr well . experimental failure was flagged and rejected based on the level of bvdv rna in each well . the level of hcv rna in each well was calculated according to a standard curve that is run in the same pcr plate . the percentage of inhibition or decrease of hcv rna level due to compound treatment was calculated using the dmso or no compound control as 0 % of inhibition . the ic50 ( concentration at which 50 % inhibition of hcv rna level is observed ) was calculated from the titration curve of any given compound . the ic50 values inhibitory activity of some of the compounds of the present invention is shown in table 1 above . the ki determinations were performed as follows . the ki values for some compounds of the present invention are recited above in table 1 . nh 2 - glu - asp - val - val -( alpha ) abu - cys - ser - met - ser - tyr - cooh stock solution of 20 mm 5ab was made in dmso w / 0 . 2m dtt . this was stored in aliquots at − 20 c . buffer : 50 mm hepes , ph 7 . 8 ; 20 % glycerol ; 100 mm nacl total assay volume was 200 μl x1 conc . in ( μl ) assay buffer 155 see above 5 mm kk4a 1 25 μm 1 m dtt 1 5 mm dmso or inhibitor 3 1 . 5 % v / v 0 . 25 μm tns3 20 25 nm 200 μm sab 20 20 μm ( initiate ) the buffer was combined with kk4a , dtt , and tns3 ; 177 μl of this solution was distributed each into wells of 96 well plate and incubated at 30 ° c . for ˜ 5 - 10 min . 3 μl of appropriate concentration of test compound dissolved in dmso ( dmso only for control ) was added to each well and incubate at 30 ° c . for 15 min . reaction was initiated by addition of 20 μl of 200 μm 5ab substrate ( 20 μm concentration is equivalent or slightly lower than the km for 5ab ) and incubated for 20 min at 30 ° c . the reaction was terminated by addition of 50 μl of 10 % tfa 200 μl aliquots were transferred to hplc vials the smsy product was isolated from substrate and kk4a by the method which follows . instrumentation : hewlett packard 1100 degasser g1322a binary pump g1312a autosampler g1313a column themostated chamber g1316a diode array detector g1315a column : phenomenex jupiter ; 5 micron c18 ; 300 angstroms ; 150 × 2 mm ; p / o 00f - 4053 - b0