Excitatory amino acid receptor modulators

A compound of the formula:

• in which:
• R represents CN or a group of formula CONR1(X1R2);
• X1 represents a bond, NHCO, NH, O or (CH2)p—Y— in which Y represents O, S, NRb, or COO and p is 2 or 3, and R1, R2 and Rb each independently represents hydrogen;
• C1-10 alkyl;
• C2-10 alkenyl;
• C2-10 alkynyl;
• aryl;
• aryl-C1-10 alkyl;
• aryl -C2-10 alkenyl;
• aryl-C2-10 alkynyl;
• heteroaryl;
• C3-8 cycloalkyl;
• C3-8-cycloalkyl-C1-10 alkyl;
• a group of formula CH(R3)COOH in which R3 represents an amino acid residue;
• or R1 and X1R2 together with the nitrogen atom to which they are attached form a 5 to 6-membered saturated heterocyclic ring, which ring may optionally be fused with an aromatic ring;
• an ester thereof;
• or a salt of said compound of formula I or said ester thereof.