Claims for Patent: 6,562,861

Summary for Patent: 6,562,861

Title:	Substituted cyclopentane and cyclopentene compounds useful as neuraminidase inhibitors
Abstract:	Compounds I-III wherein U is CH, O, or S; Z is mono- or di-substituted carbon; R is (CH2)nCO2H, (CH2)nSO3H, (CH2)nPO3H2, (CH2)nNO2, CH(SCH3)3, esters; R1 is H, hydroxyalkyl, aminoalkyl, alkoxyalkyl; RR1 is O; n is 0-4; R2, R3 is H, hydroxyalkyl, aminoalkyl, alkoxyalkyl, haloalkyl; R4 is (CH2)nOH, (CH2)nNH2, substituted alkyl were prepd. as neuraminidase inhibitors. Thus, (1R,3R,4R,1'S)-(-)-(1'-acetylamino-2 '-ethyl)butyl-4-(aminoimino)methylaminocyclopentan-1-carboxylic acid was prepd. and tested in vitro as neuraminidase inhibitor (IC50<1.mu.M).
Inventor(s):	Yarlagadda S. Babu, Pooran Chand, John A. Montgomery
Assignee:	Biocryst Pharmaceuticals Inc
Application Number:	US09/555,131
Patent Claims:	1. A compound represented by the formulae: wherein U is CH and p is 1 Z is —C(R2)(R3), —CH—N(R2)(R3), C(R3)[(CH2)nR2], CH—C(R3)(R8)(CH2)nR2, C[(CH2)nR2]—[CH(R3)(R8)], C[(R3)][CH(CH2)nR2(R8)]; R1 is H, (CH2)nOH, (CH2)nNH2, (CH2)nNR10R11, (CH2)nOR11, (CH2)nSR11, (CH2)n halogen R9 is (CH2)nCO2H, (CH2)nSO3H, (CH2)nPO3H2, (CH2)nNO2, C(SCH3)3, esters thereof, or salts thereof; or R1 R9 together represent R2 is NHC(O)R5, NHC(S)R5, NHSO2R5, C(O)NHR5, SO2NHR5, CH2S(O)R5, or CH2SO2R5; R3 and R8 individually is H, (CH2)nC(O)R10, (CH2)nCO2R10, (CH2)mOR10, CH(OR10)CH(R10)m, C(O)N(R10)m, C(O)N(OR10)R10, (CH2)nN(R10)m, CH(R10) when m is 2, (CH2)n(R10)m, CH2CH(OR10)CH2OR10, CH(OR10)CH(OR10)CH2OR10, CH2OR10, CH(OR10)CH2NHR10, CH2CH(OR10)CH2NHR10, CH(OR10)CH(OR10)CH2NHR10, C(═NR10)N(R10)m, NHR10, NHC(═NR10)N(R10)m, provided that at least one of R2, R3 and R8 is other than H; R4 is (CH2)nOH, (CH2)nOR11, (CH2)nOC(O)R11, (CH2)nNHC(═NR11)NHR11, (CH2)nNR10R11, (CH2)nNH2, (CH2)nC(═NH)(NH2), (CH2)nNHC(═NR11)NH2, (CH2)nNHC(═NR7)NH2, (CH2)nCN, (CH2)nN3, C(═NH)NH2, C(NR7)NH2, or C(NR11)NH2; R5 is H, lower alkyl, cyclo alkyl, halogen substituted alkyl, aryl, substituted aryl or CF3; R7 is H, (CH2)nOH, (CH2)nCN, (CH2)nNH2, or (CH2)nNO2; R10 is H, lower alkyl, lower alkylene, branched alkyl, cyclic alkyl, (CH2)n aromatic, (CH2)n substituted aromatic, or when m is 2 both R10 groups can also be interconnected to form an N substituted heterocyclic ring, or other 5- or 6-membered heterocyclic ring; R11 is lower alkyl, branched alkyl, (CH2)m aromatic, SO2R10, C(O)R10 or C(O)OR10; R12 and R13 is (CH2)nOH, (CH2)nNH2, (CH2)nNR10R11, (CH2)nOR11, (CH2)nF, (CH2)nOC(O)R11, or (CH2)nNHC(O)R11, and R12 can also be H; m is 1 or 2; n is 0-4; p is 0 or 1; and pharmaceutically acceptable salts thereof. 2. The compound of claim 1, wherein said lower alkyl group contains 1 to 8 carbon atoms; and said lower alkylene group contains 2 to 8 carbon atoms. 3. The compound of claim 1, wherein said lower alkyl group contains 1 to 3 carbon atoms; and said lower alkylene group contains 2 to 3 carbon atoms. 4. The compound of claim 1, wherein said alkyl group R5, R10 and R11 is selected from the group consisting of methyl, ethyl, propyl, isopropyl, t-butyl, cyclopentyl, and cyclohexyl, the aromatic group is selected from the group consisting of phenyl and alkyl substituted aromatic groups; the substituted cycloalkyl group contains 3-8 carbon atoms in the ring and are substituted with 1 or 2 alkyl groups having 1-6 carbon atoms, hydroxy group or both; and the alkylene group is selected from the group consisting of vinyl, 1-propenyl, allyl, isopropenyl, 2-methyl-2-propenyl and cyclopentenyl. 5. The compound of claim 1, wherein said salt is from acid selected from the group consisting of hydrochloric, hydrobromic, sulfuric, nitric, perchloric, fumaric, maleic, phosphoric, glycollic, lactic, salicylic, succinic, toluene-p-sulphonic, tartaric, acetic, citric, methanesulphonic, formic, benzoic, malonic, napthalene-2-sulphonic, trifluoroacetic and benzenesulphonic acids. 6. The compound of claim 1, wherein said salt is a sodium or ammonium salt. 7. A compound being selected from the group consisting of (+) 4-Azidocyclopent-2-en-1-one, (+) 3β-{(1′-acetylamino′bis(ethoxycarbonyl)}methyl-4α-azidocyclopentan-1-one, (+) 3β-{1′-Acetylamino-1′-bis(ethoxycarbonyl)}methyl-4α-tert-butoxycarbonylamino-cyclopentan-1-one, (+) 2-{3β-{1′-Acetylamino-1′-bis(ethoxycarbonyl)}methyl-4α-tert-butoxycarbonyl-amino-1-cyclopentylidene}-1,3-dithiane, (+) 2-{3β-(1′-Acetylamino-1′-carboxy)methyl-4α-tert-butoxycarbonylamino-1-cyclopentylidene}-1,3-dithiane, (+) 2-{3β-{1′-Acetylamino-1′-{(N-methoxy-N-methyl)aminocarbonyl}methyl}-4α-tert-butoxycarbonylamino-1-cyclopentylidene}-1,3-dithiane, (+) 2-{3β-(1′-Acetylamino-1′-formyl)methyl-4α-tert-butoxycarbonylamino-1-cyclopentylidene}-1,3-dithiane, (+) 2-{3β-(1′-Acetylamino-1′-ethoxycarbonyl)methyl-4α-tert-butoxycarbonylamino-1-cyclopentylidene}-1,3-dithiane, (+) 2-{3β-(1′-Acetylamino-2′-hydroxy)ethyl-4α-tert-butoxycarbonylamino-1-cyclopentylidene}-1,3-dithiane, (+) 2-{3β-(1′-acetylamino-2′-ethoxy)ethyl-4α-(tert-butoxycarbonyl)amino-1-cyclopentylidene}-1,3-dithiane, (+) Methyl-3β-(1′-acetylamino-2′-ethoxy)ethyl-4α-(tert-butoxycarbonyl)aminocyclopentan-1-carboxylate and (+) Methyl 3β-(1′-acetylamino-2′-ethoxy)ethyl-4α-aminocyclopentan-r-1-carboxylate, (+) 3β-(1′-Acetylamino-2′-ethoxy)ethyl-4α-aminocyclopentan-1-carboxylic acid, (+) 3β-(1′-Acetylamino-2′-ethoxy)ethyl-4α-{(aminoimino)methyl}aminocyclopentan-1-carboxylic acid, (+) t-3-(1′-Acetylamino-1′-di(ethoxycarbonyl)}methyl-c-4-tert-butoxycarbonylamino-t-1-(trismethylthio)methyl}cyclopentan-r-1-ol, (+) t-3-[1′-Acetylamino-1′-carboxy)}methyl-c-4-tert-butoxycarbonylamino-t-1-[(tris methylthio)methyl]cyclopentan-r-1-ol, (+) t-3-[1′-Acetylamino-1′-[(N-methoxy-N-methyl)aminocarbonyl]methyl]-c-4-tert-butoxycarbonylamino-t-1-[(trismethylthio)methyl]cyclopentan-r-1-ol, (+) t-3-(1′-Acetylamino-1′-formyl)methyl-c-4-tert-butoxycarbonylamino-t-1-[(tris methylthio)methyl]cyclopentan-r-1-ol, (+) t-3-{(1′-Acetylamino-3′-ethyl-2′-oxo)pentyl}-c-4-tert-butoxycarbonylamino-t-1-{(trismethylthio)methyl]cyclopentan-r-1-ol, (+) t-3-{(1′-Acetylamino-3′-ethyl-2′-hydroxy)pentyl}-c-4-tert-butoxycarbonylamino-t-1-{(trismethylthio)methyl}cyclopentan-r-1-ol, (+) Methyl c-3-{(1′-acetylamino-3′-ethyl-2′-hydroxy)pentyl}-t-4-tert-butoxycarbonyl-amino-t-1-hydroxycyclopentan-r-1-carboxylate, (+) Methyl c-3-{(1′-acetylamino-3′-ethyl-2′-hydroxy)pentyl}-t-4-{(tert-butoxycarbonyl-amino-tert-butoxycarbonylimino)methyl}amino-t-1-hydroxycyclopentan-r-1-carboxylate, (+) c-3-{(1′-Acetylamino-3′-ethyl-2′-hydroxy)pentyl}-t-4-{aminoiminomethyl}-amino-t-1-hydroxycyclopentan-r-1-carboxylic acid, (+) c-3-{(1′-Acetylamino-3′-ethyl-2′-hydroxy)pentyl}-t-4-{aminoiminomethyl}-amino-t-1-hydroxycyclopentan-r-1-carboxylic acid, (+) 2-{3β-(1′-Acetylamino-3′-ethyl)-2′-pentenyl-4α-tert-butoxycarbonylamino-1-cyclopentylidene}-1,3-dithiane, (+) Methyl 3β-(1′-Acetylamino-3′-ethyl)-2′-pentenyl-4α-(tert-butoxycarbonyl)amino-cyclopentan-1-carboxylate, (+) Methyl 3β-(1′-Acetylamino-3′-ethyl)-2′-pentenyl-4α-aminocyclopentan-1-carboxylate, (+) 3β-(1′-Acetylamino-3′-ethyl)-2′-pentenyl-4α-aminocyclopentan-1-carboxylic acid, (+) Methyl 3β-(1′-acetylamino-3′-ethyl)pentyl-4α-aminocyclopentan-1-carboxylate, (+) 3β-(1′-Acetylamino-3′-ethyl)pentyl-4α-aminocyclopentan-1-carboxylate, (+) Methyl 3β-(1′-Acetylamino-3′-ethyl)-2′-pentenyl-4α-aminocyclopentan-1-carboxylate, (+) Methyl 3β-(1′-acetylamino-3′-ethyl)pentyl-4α-aminocyclopentan-1-carboxylate, (+) 3β-(1′-Acetylamino-3′-ethyl)pentyl-4α-aminocyclopentan-1-carboxylic acid, (+) 2-{3β-(1′-Acetylamino)-2′-pentenyl-4α-tert-butoxycarbonylamino-1-cyclopent-ylidene}-1,3-dithiane, (+) Methyl 3β-(1′-acetylamino)-2′-pentenyl-4α-tert-butoxycarbonylaminocyclopentan-1-carboxylate, (+) Methyl 3β-(1′-acetylamino)pentyl-4α-tert-butoxyarbonylaminocyclopentan-1-carboxylate, (+) Methyl 3β-(1′-acetylamino)pentyl-4α-aminocyclopentan-1-carboxylate, (+) 3β-(1′-Acetylamino)pentyl-4α-aminocyclopentan-1-carboxylic acid, (+) Methyl cyclopent-3-ene-1-carboxylate, and (+) Ethyl cyclopent-3-ene-1-carboxylate, (+) Methyl t-3-(1′-acetylaminopentyl)-t-4-hydroxycyclopentan-r-1-carboxylate, (+) Methyl t-3-(1′-acetylaminopentyl)-t-4-hydroxycyclopentan-r-1-carboxylate, (+) Methyl t-3-(1-acetylamino-2-ethyl)butyl-t-4-hydroxycyclopentan-r-1-carboxylate, (+) Methyl t-3-[(1′-acetylamino-2′-ethyl)butyl]-t-4-hydroxycyclopentan-r-1-carboxylate, (+) Methyl t-3-(1′-acetylamino-2′-propyl)pentyl-t-4-hydroxycyclopentan-r-1-carboxylate, (+) Ethyl t-3-(1′-acetylamino-2′-cyclohexyl)ethyl-t-4-hydroxycyclopentan-r-1-carboxylate, (+) Ethyl t-3-(1′-acetylamino-2′-ethyl)hexyl-t-4-hydroxycyclopentan-r-1-carboxylate, (+) Ethyl t-3-(1′-acetylamino-2′-methyl)propyl-t-4-hydroxycyclopentan-r-1-carboxylate, (+) Ethyl t-3-(1′-acetylamino-1′-cyclohexyl)methyl-t-4-hydroxycyclopentan-r-1-carboxylate, (+) t-3-(1′-Acetylaminopentyl)-t-4-hydroxycyclopentan-r-1-carboxylic acid, (+) t-3-(1′-Acetylaminopentyl)-t-4-hydroxycyclopentan-r-1-carboxylic acid, (+) t-3-(1′-Acetylaminopentyl)-t-4-hydroxycyclopentan-r-1-carboxylic acid, (+) t-3-(1′-Acetylamino-2′-ethyl)butyl-t-4-hydroxycyclopentan-r-1-carboxylic acid, (+) t-3-(1′-Acetylamino-2′-ethyl)butyl-t-4-hydroxycyclopentan-r-1-carboxylic acid, (+) t-3-(1′-Acetylamino-2′-propyl)pentyl-t-4-hydroxycyclopentan-r-1-carboxylic acid, (+) t-3-(1′-Acetylamino-2′-cyclohexyl)ethyl-t-4-hydroxycyclopentan-r-1-carboxylic acid, (+) t-3-(1′-Acetylamino-2′-ethyl)hexyl-t-4-hydroxycyclopentan-r-1-carboxylic acid, (+) t-3-(1′-Acetylamino-2′-methyl)propyl-t-4-hydroxycyclopentan-r-1-carboxylic acid, (+) t-3-(1′-Acetylamino-1′-cyclohexyl)methyl-t-4-hydroxycyclopentan-r-1-carboxylic acid, (+) Methyl t-3-(1′-acetylaminopentyl)-t-4-methanesulfonyloxycyclopentan-r-1-carboxylate, (+) Methyl t-3-(1′-acetylaminopentyl)-t-4-methanesulfonyloxycyclopentan-r-1-carboxylate, (+) Methyl-t-3-(1′-Acetylamino-2′-ethyl)butyl-t-4-methanesulfonyloxycyclopentan-r-1-carboxylate, (+) Methyl t-3-(1′-acetylamino-2′-propyl)pentyl-t-4-methanesulfonyloxycyclopentan-r-1-carboxylate, (+) Methyl t-3-(1′-acetylaminopentyl)-c-4-azidocyclopentan-r-1-carboxylate, (+) Methyl-t-3-(1′-acetylaminopentyl)-c-4-azidocyclopentan-r-1-carboxylate, (+) Methyl t-3-[(1′-acetylamino-2′-ethyl)butyl]-c-4-azidocyclopentan-r-1-carboxylate, (+) Methyl t-3-(1′-acetylamino-2′-propyl)pentyl-c-4-azidocyclopentan-r-1-carboxylate, (+) Methyl t-3-(1′-acetylaminopentyl)-c-4-aminocyclopentan-r-1-carboxylate, (+) Methyl t-3-(1′-acetylaminopentyl)-c-4-aminocyclopentan-r-1-carboxylate, (+) Methy t-3-[(1′-acetylamino-2′-ethyl)butyl]-c-4-aminocyclopentan-r-1-carboxylate, (+) Methyl t-3-(1′-acetylamino-2′-propyl)pentyl-c-4-aminocyclopentan-r-1-carboxylate, (+) t-3-(1′-Acetylaminopentyl)-c-4-aminocyclopentan-r-1-carboxylic acid, (+) t-3-(1′-Acetylaminopentyl)-c-4-aminocyclopentan-r-1-carboxylic acid, (+) t-3-[(1′-Acetylamino-2′-ethyl)butyl]-c-4-aminocyclopentan-r-1-carboxylic acid, (+) t-3-(1′-Acetylamino-2′-propyl)pentyl-c-4-aminocyclopentan-r-1-carboxylic acid, (+) Methyl c-3-(1′-acetylaminopentyl)-c-4-hydroxycyclopentan-r-1-carboxylate, (+) c-3-(1′-Acetylaminopentyl)-c-4-hydroxycyclopentan-r-1-carboxylic acid, (+) Methyl c-3-(1′-acetylaminopentyl)-c-4-methanesulfonyloxycyclopentan-r-1-carboxylate, (+) Methyl-c-3-(1′-acetylaminopentyl)-t-4-azidocyclopentan-r-1-carboxylate, (+) Methyl c-3-(1′-acetylaminopentyl)-t-4-aminocyclopentan-r-1-carboxylate, (+) c-3-(1′-Acetylaminopentyl)-t-4-aminocyclopentan-r-1-carboxylic acid, (+) Methyl t-3-(1′-acetylaminopentyl)-c-4-{(tert-butoxycarbonylamino-tert-butoxycarbonylimino)methyl}aminocyclopentan-r-1-carboxylate, (+) Methyl t-4-(1′-acetylaminopentyl)-c-4-{(tert-butoxycarbonylamino-tert-butoxy carbonylimino)methyl}aminocyclopentan-r-1-carboxylate, (+) Methyl t-3-{(1′-acetylamino-2′-ethyl)butyl}-c-4-{(tert-butoxycarbonylamino-tert-butoxy carbonylimino)methyl}aminocyclopentan-r-1-carboxylate, (+) Methyl t-3-(1′-acetylamino-2′-propyl)pentyl-c-4-{(tert-butoxycarbonylamino-tert-butoxycarbonylimino)methyl}aminocyclopentan-r-1-carboxylate, (+) Methyl t-3-(1′-acetylaminopentyl)-c-4-{(aminoimino)methyl}aminocyclopentan-r-1-carboxylate, (+) Methyl t-3-(1′-acetylaminopentyl)-c-4-{(aminoimino)methyl}aminocyclopentan-r-1-carboxylate, (+) Methyl t-3-{(1′-acetylamino-2′-ethyl)butyl}-c-4-{(aminoimino)methyl}amino- cyclopentan-r-1-carboxylate, (+) t-3-(1′-Acetylamino-2′-propyl)pentyl-c-4-{(tert-butoxycarbonylamino-tert-butoxycarbonylimino)methyl}aminocyclopentan-r-1-carboxylic acid, (+) t-3-(1′-Acetylaminopentyl)-c-4-{(aminoimino)methyl}aminocyclopentan-r-1-carboxylic acid, (+) t-3-(1′-Acetylaminopentyl)-c-4-{(aminoimino)methyl}aminocyclopentan-r-1-carboxylic acid, (+) t-3-{(1′-Acetylamino-2′-ethyl)butyl}-c-4-{(aminoimino)methyl}aminocyclopentan-r-1-carboxylic acid, (+) t-3-(1′-Acetylamino-2′-propyl)pentyl-c-4-{(aminoimino)methyl}aminocyclopentan-r-1-carboxylic acid, (+) Methyl c-3-(1′-acetylaminopentyl)-t-4-{(tert-butoxycarbonylamino-tert-butoxy carbonylimino)methyl}aminocyclopentan-r-1-carboxylate, (+) Methyl c-3-(1′-Acetylaminopentyl)-t-4-{(aminoimino)methyl}aminocyclopentan-r-1-carboxylate, (+) c-3-(1- Acetylaminopentyl)-t-4-{(aminoimino)methyl}aminocyclopentan-r-1-carboxylic acid, (1S,4R)-(−)-4-Aminocyclopent-2-en-1-carboxylic acid, (1R,4S)-(+)-4-Aminocyclopent-2-en-1-carboxylic acid, (+)-cis-4-Aminocyclopent-2-en-1-carboxylic acid, (1S,4R)-(−)-Methyl-4-aminocyclopent-2-en-1-carboxylate, (1S,4R)-(−)-Ethyl-4-aminocyclopent-2-en-1-carboxylate, (1R,4S)-(+)-Ethyl-4-aminocyclopent-2-en-1-carboxylate, (+)-cis-Methyl-4-aminocyclopent-2-en-1-carboxylate, (+)-cis-Ethyl-4-aminocyclopent-2-en-1-carboxylate, (1S,4R)-(−)-Methyl-4-tert-butoxycarbonylaminocyclopent-2-en-1-carboxylate, (1S,4R)-(−)-Ethyl-4-tert-butoxycarbonylaminocyclopent-2-en-1-carboxylate, (1R,4S)-(+)-Ethyl-4-tert-butoxycarbonylaminocyclopent-2-en-1-carboxylate, (+)-cis-Methyl-4-tert-butoxycarbonylaminocyclopent-2-en-1-carboxylate, (+)-cis-Ethyl-4-tert-butoxycarbonylaminocyclopent-2-en-1-carboxylate, (1S,2S,3R,4R,1′S)-(−)-Methy 3-(1′-acetyamino-2′-ethyl)butyl-4-tert-butoxycarbonyl-amino-2-hydroxycyclopentan-1-carboxylate, (1S,2S,3R,4R,1′S)-(−)-Methyl 3-(1′-acetylamino-2′-propyl)pentyl-4-tert-butoxycarbonyl-amino-2-hydroxycyclopentan-1-carboxylate, (1S,2S,3R,4R,1′S)-(−)-Ethyl 3-(1′-acetylamino-2′-ethyl)butyl-4-tert-butoxycarbonyl-amino-2-hydroxycyclopentan-1-carboxylate, (1S,2S,3R,4R,1′S)-(−)-Methyl 3-(1′-acetylamino-2′-propyl)pentyl-4-tert-butoxycarbonyl-amino-2-hydroxycyclopentan-1-carboxylate, (1R,2R,3S,4S,1′R)-(+)-Ethyl 3-(1′-acetylamino-2′-ethyl)butyl-4-tert-butoxycarbonyl-amino-2-hydroxycyclopentan-1-carboxylate, (+)-Methyl t-3-(1′-acetylamino-2′-ethyl)butyl-c-4-tert-butoxycarbonylamino-t-2-hydroxycyclopentan-r-1-carboxylate, (+)-Methyl t-3-(1′-acetylamino-2′-propyl)pentyl-c-4-tert-butoxycarbonylamino-t-2-hydroxycyclopentan-r-1-carboxylate, (+)-Methyl t-3-(1′-acetylamino-3′-ethyl)pentyl-c-4-tert-butoxycarbonylamino-t-2-acetyloxycyclopentan-r-1-carboxylate, (+)-Methyl t-3-(1′-acetylamino-n-butyl)-c-4-tert-butoxycarbonylamino-t-2-acetyloxy-cyclopentan-r-1-carboxylate, (+)-Ethyl t-3-(1′-acetylamino-2′-ethyl)butyl-c-4-tert-butoxycarbonylamino-t-2-hydroxycyclopentan-r-1-carboxylate, (+)-Ethyl t-3-(1′-acetylamino-2′-methyl)butyl-c-4-tert-butoxycarbonylamino-t-2-hydroxycyclopentan-r-1-carboxylate, (+)-Ethyl t-3-(1′-acetylamino-2′-methyl)propyl-c-4-tert-butoxycarbonylamino-t-2-hydroxycyclopentan-r-1-carboxylate, (1S,2S,3R,4R,1′S)-(−)-Methyl 3-(1′-acetylamino-2′-ethyl)butyl-4-amino-2-hydroxy-cyclopentan-1-carboxylate, (1S,2S,3R,4R,1′S)-(−)-Methyl 3-(1′-acetylamino-2′-propyl)pentyl-4-amino-2-hydroxycyclopentan-1-carboxylate, (1S,2S,3R,4R,1′S)-(−)-Ethyl 3-(1′-acetylamino-2′-ethyl)butyl-4-amino-2-hydroxycyclo-pentan-1-carboxylate, 1R,2R,3S,4S,1′R)-(+)-Ethyl 3-(1′-acetylamino-2′-ethyl)butyl-4-amino-2-hydroxy-cyclopentan-1-carboxylate, (+)-Methyl t-3-(1′-acetylamino-2′-ethyl)butyl-c-4-amino-t-2-hydroxycyclopentan-r-1-carboxylate, (+)-Methyl t-3-(1′-acetylamino-2′-propyl)pentyl-c-4-amino-t-2-hydroxycyclopentan-r-1-carboxylate, (+)-Methyl t-3-(1′-acetylamino-3′-ethyl)pentyl-c-4-amino-t-2-acetyloxycyclopentan-r-1-carboxylate, (+)-Methyl t-3-(1′-acetylamino-n-butyl)-c-4-amino-t-2-acetyloxycyclopentan-r-1-carboxylate, (+)-Ethyl t-3-(1′-acetylamino-2′-ethyl)butyl-c-4-amino-t-2-hydroxycyclopentan-r-1-carboxylate, (+)-Ethyl t-3-(1′-acetylamino-2′-methyl)butyl-c-4-amino-t-2-hydroxycyclopentan-r-1-carboxylate, (+)-Ethyl t-3 -(1′-acetylamino-2′-methyl)propyl-c-4-amino-t-2-hydroxycyclopentan-r-1-carboxylate, (1S,2S,3R,4R,1′S)-(−)-3-(1′-Acetylamino-2′-ethyl)butyl-4-amino-2-hydroxycyclopentan-1-carboxylic acid, (1R,2R,3S,4S,1′R)-(+)-3-(1′-Acetylamino-2′-ethyl)butyl-4-amino-2-hydroxy-cyclopentan-1-carboxylic acid, (+)-t-3-(1′-Acetylamino-2′-ethyl)butyl-c-4-amino-t-2-hydroxycyclopentan-r-1-carboxylic acid, (+)-t-3-(1′-Acetylamino-2′-propyl)pentyl-c-4-amino-t-2-hydroxycyclopentan-r-1-carboxylic acid, (+)-t-3-(1′-Acetylamino-3′-ethyl)pentyl-c-4-amino-t-2-hydroxycyclopentan-r-1-carboxylic acid, (+)-t-3-(1′-Acetylamino-n-butyl)-c-4-amino-t-2-hydroxycyclopentan-r-1-carboxylic acid, (+)-t-3-(1′-Acetylamino-2′-methyl)butyl-c-4-amino-t-2-hydroxycyclopentan-r-1-carboxylic acid, (+)-t-3-(1′-Acetylamino-2′-methyl)propyl-c-4-amino-t-2-hydroxycyclopentan-r-1-carboxylic acid, (1S,2S,3R,4R,1′S)-(−)-Ethyl 3-(1′-acetylamino-2′-ethyl)butyl-4-{(tert-butoxycarbo-nyl-amino-tert-butoxycarbonylimino)methyl}amino-2-hydroxycyclopentan-1-carboxylate, (+)-Methyl t-3-(1′-acetylamino-2′-ethyl)butyl-c-4-{(tert-butoxycarbonylamino-tert-butoxycarbonylimino)methyl}amino-t-2-hydroxycyclopentan-r-1-carboxylate, (+)-Methyl t-3-(1′-acetylamino-3′-ethyl)pentyl-c-4-{(tert-butoxycarbonylamino-tert-butoxycarbonylimino)methyl}amino-t-2-acetyloxycyclopentan-r-1-carboxylate, (+)-Methyl t-3-(1′-acetylamino-n-butyl)-c-4-{(tert-butoxycarbonylamino-tert-butoxycarbonylimino)methyl}amino-t-2-acetyloxycyclopentan-r-1-carboxylate, (1S,2S,3R,4R,1′S)-(−)-Ethyl 3-(1′-acetylamino-2′-ethyl)butyl-4-{(N-tert-butoxycarbonyl-N-methylamino-N′-tert-butoxycarbonylimino)methyl}amino-2-hydroxycyclopentan-1-carboxylate, (1S,2S,3R,4R,1′S)-(−)-Ethyl 3-(1′-acetylamino-2′-ethyl)butyl-4-{(amino-imino)methyl}-amino-2-hydroxycyclopentan-1-carboxylate, (+)-Methyl t-3-(1′-acetylamino-2′-ethyl)butyl-c-4-{(amino-imino)methyl}amino-t-2-hydroxycyclopentan-r-1-carboxylate, (+)-Methyl t-3-(1′-acetylamino-3′-ethyl)pentyl-c-4-{(amino-imino)methyl}amino-t-2-acetyloxycyclopentan-r-1-carboxylate, (+)-Methyl t-3-(1′-acetylamino-n-butyl)-c-4-{(amino-imino)methyl}amino-t-2-acetyloxycyclopentan-r-1-carboxylate, (1S,2S,3R,4R,1′S)-(−)-Ethyl-3-(1′-acetylamino-2′-ethyl)butyl-4-{(N-methylamino-imino)methyl}amino-2-hydroxycyclopentan-1-carboxylate, (1S,2S,3R,4R,1′S)-(−)-3-(1′-Acetylamino-2′-ethyl)butyl-4-{(aminoimino) methyl}amino-2-hydroxycyclopentan-1-carboxylic acid, (+)-t-3-(1′-Acetylamino-2′-ethyl)butyl-c-4-{(amino-imino)methyl}amino-t-2-hydroxycyclopentan-r-1-carboxylic acid, (+)-t-3-(1′-Acetylamino-3′-ethyl)pentyl-c-4-{(amino-imino)methyl}amino-t-2-hydroxycyclopentan-r-1-carboxylic acid, (+)-t-3-(1′-Acetylamino-n-butyl)-c-4-{(amino-imino)methyl}amino-t-2-hydroxycyclopentan-r-1-carboxylic acid, (1S,2S,3R,4R,1′S)-(−)-3-(1′-Acetylamino-2′-ethyl)butyl-4-{(N-methylamino-imino)methyl}amino-2-hydroxycyclopentan-1-carboxylic acid, (1S,2S,3R,4R,1′S)-(−)-3-(1′-Acetylamino-2′-propyl)pentyl-4-{(amino-imino)methyl}amino-2-hydroxycyclopentan-1-carboxylic acid, (1S,2S,3R,4R,1′S)-(−)-Methyl 3-(1′-acetylamino-2′-ethyl)butyl-4-tert-butoxycarbonyl-amino-2-(N-imidazolyl-thiocarbonyloxy)cyclopentan-1-carboxylate, (1S,2S,3R,4R,1′S)-(−)-Methyl 3-(1′-acetylamino-2′-propyl)pentyl-4-tert-butoxycarbonylamino-2-(N-imidazolyl-thiocarbonyloxy)cyclopentan-1-carboxylate, (1S,2S,3R,4R,1′S)-(−)-Ethyl 3-(1′-acetylamino-2′-ethyl)butyl-4-tert-butoxycarbonyl-amino-2-(N-imidazolyl-thiocarbonyloxy)cyclopentan-1-carboxylate, (1S,2S,3R,4R,1′S)-(−)-Methyl 3-(1′-acetylamino-2′-propyl)pentyl-4-tert-butoxycarbonyl-amino-2-(N-imidazolyl-thiocarbonyloxy)cyclopentan-1-carboxylate, (+)-Methyl t-3-(1′-acetylamino-2′-ethyl)butyl-c-4-tert-butoxycarbonylamino-t-2-(N-imidazolyl-thiocarbonyloxy)cyclopentan-r-1-carboxylate, (1R,3R,4R,1′S)-(−)-Methyl 3-(1′-acetylamino-2′-ethyl)butyl-4-tert-butoxycarbonyl-aminocyclopentan-1-carboxylate, (1R,3R,4R,1′S)-(−)-Methyl 3-(1′-acetylamino-2′-propyl)pentyl-4-tert-butoxycarbonyl-aminocyclopentan-1-carboxylate, (1R,3R,4R,1′S)-(−)-Ethyl 3-(1′-acetylamino-2′-ethyl)butyl-4-tert-butoxycarbonyl-amino-cyclopentan-1-carboxylate, (1R,3R,4R,1′S)-(−)-Methyl 3-(1′-acetylamino-2′-propyl)pentyl-4-tert-butoxycarbonyl-aminocyclopentan-1-carboxylate, (+)-Methyl t-3-(1′-acetylamino-2′-ethyl)butyl-c-4-tert-butoxycarbonylaminocyclo-pentan-1-carboxylate, (1R,3R,4R,1′S)-(−)-Methyl 3-(1′-acetylamino-2′-ethyl)butyl-4-aminocyclopentan-1-carboxylate, (1R,3R,4R,1′S)-(−)-Methyl 3-(1′-acetylamino-2′-propyl)pentyl-4-aminocyclopentan-1-carboxylate, (1R,3R,4R,1′S)-(−)-Ethyl 3-(1′-acetylamino-2′-ethyl)butyl-4-aminocyclopentan-1-carboxylate, (1R,3R,4R,1′S)-(−)-Ethyl-3-(1′-acetylamino-2′-propyl)pentyl-4-aminocyclopentan-1-carboxylate, (+)-Methyl t-3-(1′-acetylamino-2′-ethyl)butyl-c-4-aminocyclopentan-1-carboxylate, (1R,3R,4R,1′S)-(−)-3-(1′-Acetylamino-2′-ethyl)butyl-4-aminocyclopentan-1-carboxylic acid, (+)-t-3-(1′-Acetylamino-2′-ethyl)butyl-c-4-aminocyclopentan-1-carboxylic acid, (1R,3R,4R,1′S)-(−)-Ethyl 3-(1′-acetylamino-2′-ethyl)butyl-4-{(tert-butoxycarbonyl-amino-tert-butoxycarbonylimino)methyl}aminocyclopentan-1-carboxylate, (1R,3R,4R,1′S)-(−)-Ethyl 3-(1′-acetylamino-2′-propyl)pentyl-4-{(tert-butoxycarbonyl-amino-tert-butoxycarbonylimino)methyl}aminocyclopentan-1-carboxylate, (+)-Methyl t-3-(1′-acetylamino-2′-ethyl)butyl-c-4-{(tert-butoxycarbonylamino-tert-butoxycarbonylimino)methyl}aminocyclopentan-r-1-carboxylate, (1R,3R,4R,1′S)-(−)-Ethyl 3-(1′-acetylamino-2′-ethyl)butyl-4-{(N-tert-butoxycarbonyl-N-methylamino-N′-tert-butoxycarbonylimino)methyl}aminocyclopentan-1-carboxylate, (1R,3R,4R,1′S)-(−)-Ethyl 3-(1′-acetylamino-2′-ethyl)butyl-4-{(amino-imino)methyl}-aminocyclopentan-1-carboxylate, (1R,3R,4R,1′S)-(−)-Ethyl 3-(1′-acetylamino-2′-propyl)pentyl-4-{(amino-imino)-methyl}aminocyclopentan-1-carboxylate, (+)-Methyl t-3-(1′-acetylamino-2′-ethyl)butyl-c-4-{(amino-imino)methyl}-aminocyclo-pentan-r-1-carboxylate, (1R,3R,4R,1′S)-(−)-Ethyl-3-(1′-acetylamino-2′-ethyl)butyl-4-{(N-methylamino-imino)methyl}aminocyclopentan-1-carboxylate, (1R,3R,4R,1′S)-(−)-3-(1′-Acetylamino-}2′-ethyl)butyl-4-(aminoimino)methyl-aminocyclopentan-1-carboxylic acid, (1R,3R,4R,1′S)-(−)-3-(1′-Acetylamino-2′-propyl)pentyl-4-{(amino-imino)methyl}aminocyclopentan-1-carboxylic acid, (+)-t-3-(1′-Acetylamino-2′-ethyl)butyl-c-4-{(amino-imino)methyl}-aminocyclopentan-r-1-carboxylic acid, (1R,3R,4R,1′S)-(−)-3 -(1′-Acetylamino-2′-ethyl)butyl-4-{(N-methylamino-imino)methyl}aminoclopentan-1-carboxylic acid, (1S,2S,3R,4R,1′S)-(−)-Methyl 3-(1′-acetylamino-2′-ethyl)butyl-4-tert-butoxy-carbonylamino-2-methanesulfonyloxycyclopentan-1-carboxylate, (3R,4R,1′S)-(−)-Methyl-3-(1′-acetylamino-2′-ethyl)butyl-4-tert-butoxycarbonyl-amino-cyclopent-1-en-1-carboxylate, (3R,4R,1′S)-(−)-Methyl 3-(1′-acetylamino-2′-ethyl)butyl-4-aminocyclopent-1-en-1-carboxylate hydrochloride, (3R,4R,1′S)-(−) 3-(1′-Acetylamino-2′-ethyl)butyl-4-aminocyclopent-1-en-1-carboxylic acid, (3R,4R,1′S)-(−)-Methyl 3-(1′-acetylamino-2′-ethyl)butyl-4-{(tert-butoxycarbonyl-amino-tert-butoxycarbonylimino)methyl}aminocyclopent-1-en-1-carboxylate, (3R,4R,1′S)-(−)-3-(1′-Acetylamino-2′-ethyl)butyl-4-{(tert-butoxycarbonylamino-tert-butoxycarbonylimino)methyl}aminocyclopent-1-en-1-carboxylic acid, (3R,4R,1′s)-(−)-3-(1′-Acetylamino-2′-ethyl)butyl-4-{(amino-imino)methyl}amino-cyclopent-1-en-1-carboxylic acid; and pharmaceutically acceptable salts thereof. 8. The compound of claim 1 being selected from the group consisting of (+) t-3-(1′-Acetylamino-2′-ethyl)butyl-t-4-hydroxycyclopentan-r-1-carboxylic acid (+) t-3-[(1′-Acetylamino-2′-ethyl)butyl]-c-4-aminocyclopentan-r-1-carboxylic acid (1S,2S,3R,4R,1′S)-(−)-3-(1′-Acetylamino-2′-ethyl)butyl-4-amino-2-hydroxycyclo pentan-1-carboxylic acid, (+)-t-3-(1′-Acetylamino-2′-ethyl)butyl-c-4-amino-t-2-hydroxycyclopentan-r-1-carboxylic acid, (+)-t-3-(1′-Acetylamino-2′-propyl)pentyl-c-4-amino-t-2-hydroxycyclopentan-r-1-carboxylic acid, (+)-t-3-(1′-Acetylamino-n-butyl)-c-4-amino-t-2-hydroxycyclopentan-r-1-carboxylic acid, (+)-t-3-(1′-Acetylamino-2′-methyl)butyl-c-4-amino-t-2-hydroxycyclopentan-r-1-carboxylic acid, (1S,2S,3R,4R,1′S)-(−)-3-(1′-Acetylamino-2′-ethyl)butyl-4-{aminoimino)methyl}amino-2-hydroxycyclopentan-1-carboxylic acid, (+)-t-3-(1′-Acetylamino-2′-ethyl)butyl-c-4-{amino-imino)methyl}amino-t-2-hydroxycyclopentan-r-1-carboxylic acid, (+)-t-3-(1′-Acetylamino-3′-ethyl)pentyl-c-4-{(amino-imino)methyl}amino-t-2-hydroxycyclopentan-r-1-carboxylic acid, (+)-t-3-(1′-Acetylamino-n-butyl)-c-4-[(amino-imino)methyl]amino-t-2-hydroxycyclopentan-r-1-carboxylic acid, (1S,2S,3R,4,R1′S)-(−)-3-(1′-Acetylamino-2′-ethyl)butyl-4-{(N-methylamino-imino)methyl}amino-2-hydroxycyclopentan-1-carboxylic acid, (1S,2S,3R,4R,1′S)-(−)-3-(1′-Acetylamino-2′-propyl)pentyl-4-{(amino-imino)methyl}amino-2-hydroxycyclopentan-1-carboxylic acid, (1R,3R,4R,1′S)-(−)-3-(1′-Acetylamino-2′-ethyl)butyl-4-aminocyclopentan-1-carboxylic acid, (+)-t-3-(1′-Acetylamino-2′-ethyl)butyl-c-4-aminocyclopentan-1-carboxylic acid, (1R,3R,4R,1′S)-(−)-3-(1′-Acetylamino-2′-ethyl)butyl-4-(aminoimino)methyl-aminocyclopentan-1-carboxylic acid, (1R,3R,4R,1′S)-(−)-3-(1′-Acetylamino-2′-propyl)pentyl-4-{(amino-imino)methyl}aminocyclopentan-1-carboxylic acid, (+)-t-3-(1′-Acetylamino-2′-ethyl)butyl-c-4-{(amino-imino)methyl}-aminocyclopentan-r-1-carboxylic acid, (1R,3R,4R,1′S)-(−)-3-(1′-Acetylamino-2′-ethyl)butyl-4-{(N-methylamino-imino)methyl}aminocyclopentan-1-carboxylic acid, (3R,4R,1′S)-(−)-3-(1′-Acetylamino-2′-ethyl)butyl-4-{(amino-imino)methyl}amino-cyclopent-1-en-1-carboxylic acid; and pharmaceutically acceptable salts thereof. 9. The compound of claim 7 being (1S,2S,3R,4R,1′S)-(−)-Methyl-3-(1′-acetylamino-2′-ethyl)butyl-4-amino-2-hydroxy-cyclopentan-1-carboxylate; or a pharmaceutically acceptable salt thereof. 10. The compound of claim 7 being (1S,2S,3R,4R,1′S)-(−)-Methyl-3-(1′-acetylamino-2′-propyl)pentyl-4-amino-2-hydroxy-cyclopentan-1-carboxylate; or a pharmaceutically acceptable salt thereof. 11. The compound of claim 7 being (1S,2S,3R,4R,1′S)-(−)-Ethyl-3-(1′-acetylamino-2′-ethyl)butyl-4-amino-2-hydroxy-cyclopentan-1-carboxylate; or a pharmaceutically acceptable salt thereof. 12. The compound of claim 9 being (1R,2R,3S,4S,1′R)-(+)-Ethyl-3-(1′-acetylamino-2′-ethyl)butyl-4-amino-2-hydroxy-cyclopentan-1-carboxylate; or a pharmaceutically acceptable salt thereof. 13. The compound of claim 7 being (1S,2S,3R,4R,1′S)-(−)-3-(1′-Acetylamino-2′-ethyl)butyl-4-amino-2-hydroxy-cyclopentan-1-carboxylic acid; or a pharmaceutically acceptable salt thereof. 14. The compound of claim 7 being (1R,2R,3S,4S,1′R)-(+)-3-(1′-Acetylamino-2′-ethyl)butyl-4-amino-2-hydroxy-cyclopentan-1-carboxylic acid; or a pharmaceutically acceptable salt thereof. 15. The compound of claim 7 being (1S,2S,3R,4R,1′S)-(−)-Ethyl-3-(1′-acetylamino-2′-ethyl)butyl-4-[(aminoimino)-methyl]amino-2-hydroxy-cyclopentan-1-carboxylate; or a pharmaceutically acceptable salt thereof. 16. The compound of claim 7 being (1S,2S,3R,4R,1′S)-(−)-Ethyl-3-(1′-acetylamino-2′-ethyl)butyl-4-[(N-methylamino-imino)methyl]amino-2-hydroxycyclopentan-1-carboxylate; or a pharmaceutically acceptable salt thereof. 17. The compound of claim 7 being (3R,4R,1′S)-(−)-Methyl-3-(1′-acetylamino-2′-ethyl)butyl-4-aminocyclopent-1-en-1-carboxylate; or a pharmaceutically acceptable salt thereof. 18. The compound of claim 7 being (3R,4R,1′S)-(−)-3-(1′-Acetylamino-2′-ethyl)butyl-4-aminocyclopent-1-en-1-carboxylic acid; or a pharmaceutically acceptable salt thereof. 19. The compound of claim 7 being (3R,4R,1′S)-(−)-3-(1′-Acetylamino-2′-ethyl)butyl-4-[(aminoimino)methyl]amino-cyclopent-1-en-1-carboxylic acid; or a pharmaceutically acceptable salt thereof. 20. The compound of claim 7 being (1S,2S,3R,4R,1′S)-(−)-3-(1′-Acetylamino-2′-ethyl)butyl-4-[(aminoimino)methyl]-amino-2-hydroxycyclopentan-1-carboxylic acid; or a pharmaceutically acceptable salt thereof. 21. The compound of claim 7 being (1S,2S,3R,4R,1′S)-(−)-3-(1′-Acetylamino-2′-ethyl)butyl-4-[(N-methylamino-imino)methyl]amino-2-hydroxycyclopentan-1-carboxylic acid; or a pharmaceutically acceptable salt thereof. 22. The compound of claim 7 being (1S,2S,3R,4R,1′S)-(−)-3-(1′-Acetylamino-2′-propyl)pentyl-4-[(aminoimino)-methyl]amino-2-hydroxycyclopentan-1-carboxylic acid; or a pharmaceutically acceptable salt thereof. 23. The compound of claim 7 being (1R,3R,4R,1′S)-(−)-Methyl-3-(1′-acetylamino-2′-ethyl)butyl-4-aminocyclopentan-1-carboxylate; or a pharmaceutically acceptable salt thereof. 24. The compound of claim 7 being (1R,3R,4R,1′S)-(−)-Ethyl-3-(1′-acetylamino-2′-ethyl)butyl-4-aminocyclopentan-1-carboxylate; or a pharmaceutically acceptable salt thereof. 25. The compound of claim 7 being (1R,3R,4R,1′S)-(−)-Ethyl-3-(1′-acetylamino-2′-propyl)pentyl-4-aminocyclo-pentan-1-carboxylate; or a pharmaceutically acceptable salt thereof. 26. The compound of claim 7 being (1R,3R,4R,1′S)-(−)-3-(1′-Acetylamino-2′-ethyl)butyl-4-aminocyclopentan-1-carboxylic acid; or a pharmaceutically acceptable salt thereof. 27. The compound of claim 7 being (1R,3R,4R,1′S)-(−)-Ethyl-3-(1′-acetylamino-2′-ethyl)butyl-4-[(aminoimino)-methyl]aminocyclopentan-1-carboxylate; or a pharmaceutically acceptable salt thereof. 28. The compound of claim 7 being (1R,3R,4R,1′S)-(−)-Ethyl-3-(1′-acetylamino-2′-ethyl)butyl-4-[(N-methylamino-imino)methyl]aminocyclopentan-1-carboxylate; or a pharmaceutically acceptable salt thereof. 29. compound of claim 7 being (1R,3R,4R,1′S)-(−)-3-(1′-Acetylamino-2′-ethyl)butyl-4-[(aminoimino)methyl]-aminocyclopentan-1-carboxylic acid; or a pharmaceutically acceptable salt thereof. 30. The compound of claim 7 being (1R,3R,4R,1′S)-(−)-3-(1′-Acetylamino-2′-propyl)pentyl-4-[(aminoimino)methyl]-aminocyclopentan-1-carboxylic acid; or a pharmaceutically acceptable salt thereof. 31. The compound of claim 7 being (1R,3R,4R,1′S)-(−)-3-(1′-Acetylamino-2′-ethyl)butyl-4-[(N-methylamino-imino)methyl]aminocyclopentan-1-carboxylic acid; or a pharmaceutically acceptable salt thereof. 32. The compound of claim 7 being (1S,2S,3R,4R,1′S)-(−)-3-(1′-Acetylamino-2′-propyl)pentyl-4-amino-2-hydroxy-cyclopentan-1-carboxylic acid; or a pharmaceutically acceptable salt thereof. 33. The compound of claim 7 being (1R,2R,3S,4S,1′R)-(+)-3-(1′-Acetylamino-2′-propyl)pentyl-4-amino-2-hydroxy-cyclopentan-1-carboxylic acid; or a pharmaceutically acceptable salt thereof. 34. The compound of claim 7 being (1R,2R,3S,4S,1′R)-(+)-3-(1′-Acetylamino-2′-ethyl)butyl-4-[(aminoimino)-methyl]-amino-2-hydroxycyclopentan-1-carboxylic acid; or a pharmaceutically acceptable salt thereof. 35. The compound of claim 7 being (1R,2R,3S,4S,1′R)-(+)-3-(1′-Acetylamino-2′-propyl)pentyl-4-[(aminoimino)-methyl]amino-2-hydroxycyclopentan-1-carboxylic acid; or a pharmaceutically acceptable salt thereof. 36. The compound of claim 7 being (1R,3R,4R,1′S)-(−)-3-(1′-Acetylamino-2′-propyl)pentyl-4-aminocyclo-pentan-1-carboxylic acid; or a pharmaceutically acceptable salt thereof. 37. The compound of claim 7 being (1S,3S,4S,1′R)-(+)-3-(1′-Acetylamino-2′-ethyl)butyl-4-aminocyclopentan-1-carboxylic acid; or a pharmaceutically acceptable salt thereof. 38. The compound of claim 7 being (1S,3S,4S,1′R)-(+)-3-(1′-Acetylamino-2′-ethyl)butyl-4-[(aminoimino)methyl]-aminocyclopentan-1-carboxylic acid; or a pharmaceutically acceptable salt thereof. 39. The compound of claim 7 being (1S,3S,4S,1′R)-(+)-3-(1′-Acetylamino-2′-propyl)pentyl-4-[(aminoimino)methyl]-aminocyclopentan-1-carboxylic acid; or a pharmaceutically acceptable salt thereof. 40. A composition for inhibiting influenza virus nueraminidase, comprising: a pharmaceutically acceptable carrier and an amount effective for inhibiting influenza virus nueraminidase of a compound according to claim 1. 41. A method of treating influenza virus infection, comprising the step of: administering to a patient in need thereof a pharmaceutically acceptable carrier and an amount effective for inhibiting influenza virus nueraminidase of a compound according to claim 1.