The activity of five glutamic acid analogues substituted in position 3 or 4 by a methyl ( 3T, 3E, 4T, and 4E) or a methylene group ( 4M) has been examined at one cloned Glu receptor subtype, MGluR 1. These analogues interact with glutamate receptors of the central nervous system, especially the ligand 4T [(2 S,4 S)-4-methylglutamic acid] at the metabotropic glutamate receptor mGluR 1. It was observed that only the 4T isomer is as potent an agonist as glutamic acid, whereas other isomers are less active. Furthermore, 4E [(2 S,4 R)-4-methylglutamic acid] exhibited an exceptional selectivity for the KA ionotropic receptor subtype while 4M [(2 S)-4-methyleneglutamic acid] was active at the NMDA receptors. These molecules represent suitable tools among a population of similar glutamate analogues for a classical structure-function relationship study. We have undertaken a conformational analysis by 1H and 13C NMR spectroscopy and molecular modelling of these molecules. Hetero- and homonuclear coupling constants were measured in order to assign the diastereotopic methylene protons at C(3) or C(4), and used for comparison in molecular dynamics (MD) simulations. The hydrogen-bonding possibility, steric effects or electrostatic interactions may be a considerable influence in stabilizing a conformational population in D 2O solution. The conformations may be grouped by the two backbone torsion angles, χ 1 [α-CO − 2-C(2)-C(3)-C(4)] and χ 2 [ +NC(2)-C(3)-C(4)-γCO − 2] and by the two characteristic distances between the potentially active functional groups, αN ???—γCO − 2 ( d 2) and αCO − 2—γCO − 2 ( d 2). The conformational preferences in solution of 4T, 4E and ( 3T, 3E, 4M) are discussed in the light of the physical features known for a specific metabotropic agonist (ACPD) and specific ionotropic agonists (KA) and (NMDA), respectively.