This invention relates to synthetic excitatory amino acid prodrugs of formula (I), wherein R is CO2R and R is hydrogen or fluoro; or R is hydrogen or fluoro and R is CO2R ; R and R are, independently, hydrogen, (1-10C) alkyl, (2-4C) alkenyl, aryl or arylalkyl; A is (Q)p; p is an integer from 1-10; and Q is independently selected, each time taken, from the group amino acyl; provided that the compound is not one in which R is CO2R ; R , R and R are hydrogen; p is any integer from 1-10; and Q is independently selected, each time taken, from the group amino acyl; provided that the compound is not one in which R is CO2R ; R , R and R are hydrogen; p is 1; and Q is L-alanyl; or a pharmaceutically acceptable salt thereof and processes for their preparation. The invention further relates to methods of using, and pharmaceutical compositions comprising, the compounds for the treatment of neurological disorders and psychiatric disorders.