Process for the preparation of enantiomerically enriched indoline-2-carboxylic acid

Process for the preparation of an enantiomerically enriched optionally substituted indoline-2-carboxylic acid according to formula (1)

• or a salt thereof, in which Y is an hydroxyl group, a substituted or non-substituted alkoxy group with 1-10 carbon atoms, a substituted or non-substituted aryloxy group or an amine residue, and in which Z represents one or more substituents on an aromatic group that are chosen from the group consisting of hydrogen, an hydroxyl group, an optionally substituted cyclic or acyclic aliphatic group with 1-10 carbon atoms, an optionally substituted aliphatic heterocyclic group with 1-10 carbon atoms, an optionally substituted (hetero)aryl group, an optionally substituted alkoxy group with 1-10 carbon atoms, a halogen atom, an amine group, a nitro group, a carboxylic acid, a carboxylic ester, a carboxylic amide, nitril and trifluoromethyl group, wherein an enantiomerically enriched chiral ortho-X-substituted phenylalanine compound according to formula (2)
• or a salt thereof, in which Y and Z are as defined above and X is a leaving group, is subjected to cyclisation at a temperature of below about 140° C., upon formation of the enantiomerically enriched indoline-2-carboxylic acid compound according to formula (1).