or a pharmaceutically acceptable salt thereof, wherein

R₁ is selected from hydrogen, alkyl, alkanoyl, arylalkyl, and arylalkanoyl, wherein

the arylalkyl and arylalkanoyl groups are unsubstituted or substituted with 1, 2, 3, 4, or 5 R₆ groups;

R₆ at each occurrence is independently selected from halogen, hydroxy, —NO₂, —CO₂R₁₀, —CN, alkyl, alkoxy, haloalkyl, and haloalkoxy;

R₂ is selected from hydrogen, alkyl, alkoxy, alkanoyl, arylalkyl and arylalkanoyl, wherein

the arylalkyl and arylalkanoyl groups are unsubstituted or substituted with 1, 2, 3, 4, or 5 R₆ groups;

R₃ is —Z—Q—J, wherein

Z is selected from alkyl, alkoxyalkyl, alkylthioalkyl, and alkenyl, each of which is unsubstituted or substituted with 1 or 2 groups that are independently selected from alkoxy, hydroxy, and halogen;

Q is selected from a direct bond between Z and J, —C(═O)—, aryl, heteroaryl, and heterocycloalkyl, wherein

the aryl, heteroaryl, or heterocycloalkyl group is unsubstituted or substituted with 1 or 2 groups that are independently selected from alkyl, halogen, —NR₈R₉, and alkoxy;

J is —C(═NR₇)NR₈R₉ or —NH—C(═NR₇)NR₈R₉ wherein

R₇ is selected from H, CN, NO₂, alkyl, alkanoyl, arylalkanoyl and —C(═O)NR₁₀R₁₁, wherein

R₁₀ and R₁₁ are independently selected from H, and alkyl, and

R₈ and R₉ are independently selected from H, alkyl, hydroxy, alkoxy, alkoxyalkyl, heterocycloalkylalkyl, arylalkyl, and heteroarylalkyl, wherein each of the above is unsubstituted or substituted with 1, 2, 3, or 4 R₆ groups; or

R₈ and R₉ and the nitrogen to which they are attached form a 5, 6 or 7 membered heterocycloalkyl ring, which is unsubstituted or substituted with 1, 2, or 3 groups that are independently selected from alkyl, alkoxy, hydroxy, and halogen;

or

R₇, R₈, and the nitrogens to which they are attached form a 5, 6 or 7 membered heterocycloalkyl group that is unsubstituted or substituted with 1, 2 or 3 groups that are independently selected from alkyl, alkoxy, hydroxy, and halogen; and

R₉ is selected from H, alkyl, hydroxy, alkoxy, alkoxyalkyl, heterocycloalkylalkyl, arylalkyl, and heteroarylalkyl, wherein each of the above is unsubstituted or substituted with 1, 2, 3, or 4 R₆ groups;

R₄ is selected from H, alkyl, and arylalkyl, wherein the arylalkyl group is unsubstituted or substituted with 1, 2, 3, 4, or 5 R₆ groups; and

R₅ is —M—G—A, wherein

M is aryl, wherein M is unsubstituted or substituted with 1, 2, 3, or 4 groups that are independently selected from halogen, alkyl, hydroxy, alkoxy, haloalkyl, —CN, haloalkoxy, and hydroxyalkyl;

G is selected from a direct bond between M and A, CH₂, -alkyl-O—, —O-alkyl-, O, S, SO, and SO₂;

A is aryl, wherein A is unsubstituted or substituted with 1, 2, 3, 4, or 5 groups that are independently selected from halogen, alkyl, alkoxy, haloalkyl, aryloxy, heteroaryloxy, arylalkoxy, heteroarylalkoxy, haloalkoxy, —CN, and NO₂;

with the proviso that when M is phenyl, G is a direct bond between M and A, and A is phenyl, then at least one of the four remaining hydrogens on the phenyl ring of M, of M—G—A, must be substituted with a group independently selected from halogen, alkyl, hydroxy, alkoxy, haloalkyl, —CN, haloalkoxy, and hydroxyalkyl.