Synthesis, labelling and evaluation of hydantoin-substituted indole carboxylic acids as potential ligands for positron emission tomography imaging of the glycine binding site of the N-methyl-d-aspartate receptor

The N-methyl- d-aspartate (NMDA) receptor as a type of ionotropic glutamatergic receptors is essential for physiological processes such as learning, memory and synaptic plasticity. A glutamate-induced overactivation of these receptors, accompanied by increased intracellular calcium concentration, causes cell injury and leads to a large number of acute or chronic neurological disorders, such as stroke, trauma, Parkinson's disease and Alzheimer's disease. In an attempt to visualise the glutamatergic neurotransmission in vivo with positron emission tomography, novel fluoroethoxy- and methoxy-substituted reference compounds based on the lead structure of a hydantoin-substituted indole-2-carboxy…