R² is an alkyl, aryl, cycloalkyl, cycloalkylalkyl or aralkyl radical, which radical is optionally substituted with a radical selected from the group consisting of alkyl, halo, nitro, cyano, CF₃, —OR⁹, and —SR⁹, wherein R⁹ is a radical selected from the group consisting of hydrogen and alkyl;

R³ is a hydrogen, alkyl, haloalkyl, alkenyl, alkynyl, hydroxyalkyl, alkoxyalkyl, alkylthioalkyl, alkylsulfonylalkyl, cycloalkyl, cycloalkylalkyl, heterocycloalkyl, heteroaryl, heterocycloalkylalkyl, aryl, aralkyl, heteroaralkyl, aminoalkyl or mono- or disubstituted aminoalkyl radicals, wherein said substituents are selected from the group consisting of alkyl, aryl, aralkyl, cycloalkyl, cycloalkylalkyl, heteroaryl, heteroaralkyl, heterocycloalkyl and heterocycloalkylalkyl radicals; or where said aminoalkyl radical is disubstituted, said substituents along with the nitrogen atom to which they are attached, form a heterocycloalkyl or a heteroaryl radical;

R⁴ is an alkyl, haloalkyl, alkenyl, alkynyl, hydroxyalkyl, alkoxyalkyl, cycloalkyl, cycloalkylalkyl, heterocycloalkyl, heteroaryl, heterocycloalkylalkyl, aryl, aralkyl, aralkenyl, or heteroaralkyl;

R⁶ is a hydrogen or alkyl radical;

x is 1 or 2;

t is 0 or 1; and

Y is O or S; and

A is an alkoxy, alkenoxy, aralkoxy, alkyl, cycloalkyl, cycloalkylalkoxy, cycloalkylalkyl, aralkyl, aryl, aryloxy, heterocycloalkyl, heterocycloalkoxy, heterocycloalkylalkyl, heterocycloalkylalkoxy, heteroaralkyl, heteroaralkoxy, heteroaryloxy, heteroaryl, alkenyl, aryloxyalkyl, heteroaryloxyalkyl, hydroxyalkyl, amino, or mono- or disubstituted amino radical, wherein the substituents are selected from the group consisting of alkyl, aryl, aralkyl, cycloalkyl, cycloalkylalkyl, heteroaryl, heteroaralkyl, heterocycloalkyl and heterocycloalkyalkyl radicals; or where said amino radical is disubstituted, said substituents along with the nitrogen atom to which they are attached form a heterocycloalkyl or heteroaryl radical; or is represented by the formula

R′ is a radical as defined for R³ or R″SO₂—, wherein R″ is a radical as defined for R³; or R and R′ together with the nitrogen to which they are attached form a heterocycloalkyl or heteroaryl radical;

R¹ is a hydrogen, —CO₂CH₃, —CH₂CO₂CH₃, —CO₂H, —CH₂CO₂H, —CH₂CH₂CONH₂, —CH₂CONH₂, —CONH₂, —CH₂C(O)NHCH₃, —CH₂C(O)N(CH₃)₂, —CONHCH₃, —CONH(CH₃)₂, —CH₂SO₂NH₂, —CH₂CH₂SO₂NH₂, —CH₂S[O]CH₃, —CH₂S[O]₂CH₃, —C(CH₃)₂(SCH₃), —C(CH₃)₂(S[O]CH₃), —C(CH₃)₂(S[O]₂CH₃), alkyl, hydroxyalkyl, cyanoalkyl, haloalkyl, alkenyl, alkynyl, cycloalkyl, cycloalkylalkyl, alkylthioalkyl, aralkyl, heteroaralkyl, aminoalkyl or mono- or disubstituted aminoalkyl radical, wherein said substituents are selected from the group consisting of alkyl, aryl, aralkyl, cycloalkyl, cycloalkylalkyl, heteroaryl, heteroaralkyl, heterocycloalkyl and heterocycloalkylalkyl radicals; or where said aminoalkyl radical is disubstituted, said substituents along with the nitrogen atom to which they are attached, form a heterocycloalkyl or a heteroaryl radical; and

each of R^1′ and R^1″ are independently a radical as defined for R¹; or one of R^1′ and R^1″ together with R¹ and the carbon atoms to which R¹, R^1′ and R^1″ are attached, form a cycloalkyl radical,

wherein aryl is a phenyl or naphthyl radical optionally substituted with alkyl, alkoxy, halo, hydroxyl, amino, nitro, cyano, haloalkyl, carboxy, alkoxycarbonyl, cycloalkyl, heterocycloalkyl, amido, monoalkyl substituted amino, dialkyl substituted amino, monoalkyl substituted amido, or dialkyl substituted amido.