A compound of the following formula: wherein, independently for each occurrence, A is a monocyclic ring of 4-7 atoms containing 0-2 heteroatoms, a bicyclic ring of 8-12 atoms containing 0-4 heteroatoms or a tricyclic ring of 8-12 atoms containing 0-6 heteroatoms wherein the rings are independently aliphatic, aromatic, heteroaryl or heterocyclic in nature, the heteroatoms are selected from N, S and O, and the rings are optionally substituted with one or more groups selected from C 1-4 alkyl, OR", CN, OCF 3, F, Cl, Br and I; wherein R" is H, alkyl, aralkyl, or heteroaralkyl; R' is H or alkyl; and R is wherein, independently for each occurrence, R 3 is H, alkyl, carbonyl, sulfonyl, or aryl; wherein the term "carbonyl" refers to a moiety of one of the following general formulae: wherein X50 is a bond or represents an oxygen or a sulfur, and R55 and R56 represent a hydrogen, an alkyl, an alkenyl, -(CH 2) m -R61 or a pharmaceutically acceptable salt, wherein R61 represents an aryl, a cycloalkyl, a cycloalkenyl, a heterocycle or a polycycle; and m is zero or an integer in the range of 1 to 8; and wherein the term "sulfonyl" refers to a moiety of the following general formula: in which R58 is one of the following: hydrogen, alkyl, alkenyl, alkynyl, cycloalkyl, heterocyclyl, aryl or heteroaryl; or a pharmaceutically acceptable salt thereof. A is a monocyclic ring of 4-7 atoms containing 0-2 heteroatoms, a bicyclic ring of 8-12 atoms containing 0-4 heteroatoms or a tricyclic ring of 8-12 atoms containing 0-6 heteroatoms wherein the rings are independently aliphatic, aromatic, heteroaryl or heterocyclic in nature, the heteroatoms are selected from N, S and O, and the rings are optionally substituted with one or more groups selected from C 1-4 alkyl, OR", CN, OCF 3, F, Cl, Br and I; wherein R" is H, alkyl, aralkyl, or heteroaralkyl; R' is H or alkyl; and R is wherein, independently for each occurrence, R 3 is H, alkyl, carbonyl, sulfonyl, or aryl; wherein the term "carbonyl" refers to a moiety of one of the following general formulae: wherein X50 is a bond or represents an oxygen or a sulfur, and R55 and R56 represent a hydrogen, an alkyl, an alkenyl, -(CH 2) m -R61 or a pharmaceutically acceptable salt, wherein R61 represents an aryl, a cycloalkyl, a cycloalkenyl, a heterocycle or a polycycle; and m is zero or an integer in the range of 1 to 8; and wherein the term "sulfonyl" refers to a moiety of the following general formula: in which R58 is one of the following: hydrogen, alkyl, alkenyl, alkynyl, cycloalkyl, heterocyclyl, aryl or heteroaryl; or a pharmaceutically acceptable salt thereof. wherein, independently for each occurrence, R 3 is H, alkyl, carbonyl, sulfonyl, or aryl; wherein the term "carbonyl" refers to a moiety of one of the following general formulae: wherein X50 is a bond or represents an oxygen or a sulfur, and R55 and R56 represent a hydrogen, an alkyl, an alkenyl, -(CH 2) m -R61 or a pharmaceutically acceptable salt, wherein R61 represents an aryl, a cycloalkyl, a cycloalkenyl, a heterocycle or a polycycle; and m is zero or an integer in the range of 1 to 8; and wherein the term "sulfonyl" refers to a moiety of the following general formula: in which R58 is one of the following: hydrogen, alkyl, alkenyl, alkynyl, cycloalkyl, heterocyclyl, aryl or heteroaryl; or a pharmaceutically acceptable salt thereof. wherein X50 is a bond or represents an oxygen or a sulfur, and R55 and R56 represent a hydrogen, an alkyl, an alkenyl, -(CH 2) m -R61 or a pharmaceutically acceptable salt, wherein R61 represents an aryl, a cycloalkyl, a cycloalkenyl, a heterocycle or a polycycle; and m is zero or an integer in the range of 1 to 8; and wherein the term "sulfonyl" refers to a moiety of the following general formula: in which R58 is one of the following: hydrogen, alkyl, alkenyl, alkynyl, cycloalkyl, heterocyclyl, aryl or heteroaryl; or a pharmaceutically acceptable salt thereof. in which R58 is one of the following: hydrogen, alkyl, alkenyl, alkynyl, cycloalkyl, heterocyclyl, aryl or heteroaryl; or a pharmaceutically acceptable salt thereof.