Excitatory amino acid derivatives

A process for the preparation of a compound of formula I which comprises

• (a) hydrolyzing a compound of formula ##STR15## in which R.sup.1 represents a hydrogen atom or an acyl group and R.sup.2 represents a carboxyl group or an esterified carboxyl group, or a salt thereof;
• (b) hydrolyzing a compound of formula ##STR16## in which R.sup.3 represents a carboxyl group or an esterified carboxyl group, and R.sup.4 and R.sup.5 each independently represent a hydrogen atom, a (2-6C) alkanoyl group, a (1-4C) alkyl group, a (3-4C) alkanoyl group or a phenyl (1-4C) alkyl group in which the phenyl is unsubstituted or substituted by halogen, (1-4C) alkyl or (1-4C) alkoxy, or a salt thereof;
• or
• (c) deprotecting a compound of formula ##STR17## in which R.sup.6 represents a hydrogen atom or a nitrogen protecting group and each of R.sup.7 and R.sup.8 independently represent a hydrogen atom or a carboxyl protecting group, or a salt thereof;
• whereafter, if necessary and/or desired
• (i) resolving the compound of formula I;
• (ii) converting the compound of formula I into a non-toxic metabolically labile ester or amide thereof;
• and/or;
• (iii) converting the compound of formula I or a non-toxic metabolically labile ester or amide thereof into a pharmaceutically acceptable salt thereof.

A compound of the formula ##STR18## in which X represents O, NR.sup.a, S, SO or SO.sub.2 ;

• R represents a hydrogen atom;
• a (1-6C) alkyl group;
• a (2-6C) alkenyl group;
• a (2-6C) alkynyl group;
• an optionally substituted aromatic group;
• an optionally substituted heteroaromatic group;
• a non-aromatic carbocyclic group;
• a non-aromatic heterocyclic group;
• a non-aromatic monocyclic carbocyclic group fused with one or two monocyclic aromatic or heteroaromatic groups;
• a non-aromatic monocyclic heterocyclic group fused with one or two monocyclic aromatic or heteroaromatic groups;
• or a (1-6C) alkyl, (2-6C) alkenyl or (2-6C) alkynyl group which is substituted by one, two or three groups selected independently from an optionally substituted aromatic group, an optionally substituted heteroaromatic group, a non-aromatic carbocyclic group, a non-aromatic heterocyclic group, a non-aromatic monocyclic carbocyclic group fused with one or two monocyclic aromatic or heteroaromatic groups and a non-aromatic monocyclic heterocyclic group fused with one or two monocyclic aromatic or heteroaromatic groups;
• R.sup.a represents hydrogen or a group of formula (CO).sub.n R.sup.b ;
• n is 0 or 1;
• and R.sup.b is as defined for R;
• R.sup.1 represents a hydrogen atom or an acyl group and R.sup.2 represents a carboxyl group or an esterified carboxyl group, or a salt thereof.

A compound of the formula ##STR19## in which X represents O, NR.sup.a, S, SO or SO.sub.2 ;

• R represents a hydrogen atom;
• a (1-6C) alkyl group;
• a (2-6C) alkenyl group;
• a (2-6C) alkynyl group;
• an optionally substituted aromatic group;
• an optionally substituted heteroaromatic group;
• a non-aromatic carbocyclic group;
• a non-aromatic heterocyclic group;
• a non-aromatic monocyclic carbocyclic group fused with one or two monocyclic aromatic or heteroaromatic groups;
• a non-aromatic monocyclic heterocyclic group fused with one or two monocyclic aromatic or heteroaromatic groups;
• or a (1-6C) alkyl, (2-6C) alkenyl or (2-6C) alkynyl group which is substituted by one, two or three groups selected independently from an optionally substituted aromatic group, an optionally substituted heteroaromatic group, a non-aromatic carbocyclic group, a non-aromatic heterocyclic group, a non-aromatic monocyclic carbocyclic group fused with one or two monocyclic aromatic or heteroaromatic groups and a non-aromatic monocyclic heterocyclic group fused with one or two monocyclic aromatic or heteroaromatic groups;
• R.sup.a represents hydrogen or a group of formula (CO).sub.n R.sup.b ;
• n is 0 or 1;
• and R.sup.b is as defined for R;
• R.sup.3 represents a carboxyl group or an esterified carboxyl group, and R.sup.4 and R.sup.5 each independently represent a hydrogen atom, a (2-6C) alkanoyl group, a (1-4C) alkyl group, a (3-4C) alkenyl group or a phenyl (1-4C) alkyl group in which the phenyl is unsubstituted or substituted by halogen, (1-4C) alkyl or (1-4C) alkoxy, or a salt thereof.

A compound of the formula ##STR20## in which X represents O, NR.sup.a, S, SO or SO.sub.2 ;

• R represents a hydrogen atom;
• a (1-6C) alkyl group;
• a (2-6C) alkenyl group;
• a (2-6C) alkynyl group;
• an optionally substituted aromatic group;
• an optionally substituted heteroaromatic group;
• a non-aromatic carbocyclic group;
• a non-aromatic heterocyclic group;
• a non-aromatic monocyclic carbocyclic group fused with one or two monocyclic aromatic or heteroaromatic groups;
• a non-aromatic monocyclic heterocyclic group fused with one or two monocyclic aromatic or heteroaromatic groups;
• or a (1-6C) alkyl, (2-6C) alkenyl or (2-6C) alkynyl group which is substituted by one, two or three groups selected independently from an optionally substituted aromatic group, an optionally substituted heteroaromatic group, a non-aromatic carbocyclic group, a non-aromatic heterocyclic group, a non-aromatic monocyclic carbocyclic group fused with one or two monocyclic aromatic or heteroaromatic groups and a non-aromatic monocyclic heterocyclic group fused with one or two monocyclic aromatic or heteroaromatic groups;
• R.sup.a represents hydrogen or a group of formula (CO).sub.n R.sup.b ;
• n is 0 or 1;
• and R.sup.b is as defined for R;
• R.sup.6 represents a hydrogen atom or a nitrogen protecting group and each of R.sup.7 and R.sup.8 independently represent a hydrogen atom or a carboxyl protecting group, or a salt thereof.