Amino acids with affinity for the alpha-2-delta-protein

A compound of formula IA

• or a pharmaceutically acceptable salt thereof;
• wherein R1 is hydrogen or (C1-C3)alkyl optionally substituted with from one to five fluorine atoms;
• R2 is hydrogen or (C1-C3)alkyl optionally substituted with from one to five fluorine atoms;
• and
• R3 is (C1-C6)alkyl, (C3-C6)cycloalkyl, (C3-C6)cycloalkyl-(C1-C3)alkyl, phenyl, phenyl-(C1-C3)alkyl, or phenyl-N(H)—, wherein each alkyl is optionally substituted with from one to five fluorine atoms, and each phenyl is optionally substituted with from one to three substituents independently selected from chloro, fluoro, amino, nitro, cyano, (C1-C3)alkylamino, (C1-C3)alkyl optionally substituted with from one to three fluorine atoms, and (C1-C3)alkoxy optionally substituted with from one to three fluorine atoms;
• with the proviso that when R1 is hydrogen, R2 is not hydrogen.