In this paper we describe the rational design, synthesis and pharmacological evaluation of two new stereoisomeric (S)-glutamate (Glu) analogues. The rational design was based on hybrid structures of the natural product kainic acid, a synthetic analogue CPAA and the high-affinity Glu analogue SYM2081. Pharmacological evaluation of the two stereoisomers revealed that one stereoisomer showed a subtype selectivity profile with low micromolar affinity for GluK1 and GluK3 and a 10- to 15-fold lower affinity for GluK2. The other stereoisomer displayed full selectivity for the KA over AMPA and NMDA receptors (GluK1-3: 0.39, 0.51 and 0.099¿µM, respectively).