It is intended to provide a bicyclic ³-amino acid derivative having excellent activity as an ± 2 ´ ligand. The present invention provides a compound represented by the general formula (I): wherein R 1 , R 2 , R 2' , R 4 , R 5 , R 6 , R 7 , R 8 , and R 8' are a hydrogen atom or the like； and R 3 is a hydrogen atom, a halogen atom, a C1-C6 alkyl group, or the like.
