Synthesis and biological evaluation of D-amino acid oxidase inhibitors

D-Amino acid oxidase (DAAO) catalyzes the oxidation of D-amino acids including D-serine, a full agonist at the glycine site of the NMDA receptor. A series of benzo[d]isoxazol-3-ol derivatives were synthesized and evaluated as DAAO inhibitors. Among them, 5-chlorobenzo[d]isoxazol-3-ol (CBIO) potently inhibited DAAO with an IC(50) in the submicromolar range. Oral administration of CBIO in conjunction with D-serine enhanced the plasma and brain levels of D-serine in rats compared to the oral administration Of D-serine alone.