A compound of Formula I or a pharmaceutically acceptable salt or solvate thereof, wherein: R is H or alkyl; R 1 is heteroaryl, wherein said heteroaryl is selected from the group consisting of pyridyl, each of which independently is unsubtituted or substituted with one to four substitutents independently selected from the group consisting of alkyl, and alkoxy; or R 1 is aryl, wherein said aryl is selected from the group consisting of: R 2 is H or alkyl; m is 1 or 2; n is 1 or 2; each R 3 independently is selected from the group consisting of halo, hydroxyl, alkoxy, alkyl, aryloxy, -NR 4 R 5, -C(=O)NR 4 R 5, -N(R 4)-C(=O)-R 5; -C(=O)-aryl, -C(=O)-O-alkyl, -C(=N-OH)-aryl, and -C(=O)OH; R 4 and R 5 independently are hydrogen or alkyl; alkyl is unsubstituted or optionally substituted by one or more substituents which may be the same or different, each substituent being independently selected from the group consisting of halo, alkyl, aryl, cycloalkyl, heterocyclyl, heteroaryl, cyano, hydroxy, alkoxy, alkylthio, amino, - NH(alkyl), -NH(cycloalkyl), -N(alkyl) 2, -O-C -alkyl, -O-C -aryl, -O-C -cycloalkyl, carboxy and -C O-alkyl; and each of aryl and heteroaryl is independently optionally substituted by one or more substituents, which may be the same or different, each being independently selected from the group consisting of alkyl, alkenyl, alkynyl, aryl, heteroaryl, hydroxy, hydroxyalkyl, alkoxy, aryloxy, acyl, aroyl, halo, nitro, cyano, carboxy, alkoxycarbonyl, aryloxycarbonyl, alkylsulfonyl, arylsulfonyl, heteroarylsulfonyl, alkylthio, arylthio, heteroarylthio, cycloalkyl, heterocyclyl, - C(=N-CN)-NH 2, -C(=NH)-NH 2, -C(=NH)-NH(alkyl), Y 1 Y 2 N-, Y 1 Y 2 N-alkyl-, Y 1 Y 2 NC -, Y 1 Y 2 NSO 2 - and -SO 2 NY 1 Y 2, wherein Y 1 and Y 2 can be the same or different and are independently selected from the group consisting of hydrogen, alkyl, aryl, cycloalkyl, heterocyclyl and heteroaryl. R is H or alkyl; R 1 is heteroaryl, wherein said heteroaryl is selected from the group consisting of pyridyl, each of which independently is unsubtituted or substituted with one to four substitutents independently selected from the group consisting of alkyl, and alkoxy; or R 1 is aryl, wherein said aryl is selected from the group consisting of: R 2 is H or alkyl; m is 1 or 2; n is 1 or 2; each R 3 independently is selected from the group consisting of halo, hydroxyl, alkoxy, alkyl, aryloxy, -NR 4 R 5, -C(=O)NR 4 R 5, -N(R 4)-C(=O)-R 5; -C(=O)-aryl, -C(=O)-O-alkyl, -C(=N-OH)-aryl, and -C(=O)OH; R 4 and R 5 independently are hydrogen or alkyl; alkyl is unsubstituted or optionally substituted by one or more substituents which may be the same or different, each substituent being independently selected from the group consisting of halo, alkyl, aryl, cycloalkyl, heterocyclyl, heteroaryl, cyano, hydroxy, alkoxy, alkylthio, amino, - NH(alkyl), -NH(cycloalkyl), -N(alkyl) 2, -O-C -alkyl, -O-C -aryl, -O-C -cycloalkyl, carboxy and -C O-alkyl; and each of aryl and heteroaryl is independently optionally substituted by one or more substituents, which may be the same or different, each being independently selected from the group consisting of alkyl, alkenyl, alkynyl, aryl, heteroaryl, hydroxy, hydroxyalkyl, alkoxy, aryloxy, acyl, aroyl, halo, nitro, cyano, carboxy, alkoxycarbonyl, aryloxycarbonyl, alkylsulfonyl, arylsulfonyl, heteroarylsulfonyl, alkylthio, arylthio, heteroarylthio, cycloalkyl, heterocyclyl, - C(=N-CN)-NH 2, -C(=NH)-NH 2, -C(=NH)-NH(alkyl), Y 1 Y 2 N-, Y 1 Y 2 N-alkyl-, Y 1 Y 2 NC -, Y 1 Y 2 NSO 2 - and -SO 2 NY 1 Y 2, wherein Y 1 and Y 2 can be the same or different and are independently selected from the group consisting of hydrogen, alkyl, aryl, cycloalkyl, heterocyclyl and heteroaryl.