The present invention provides a β-benzyloxyaspartic acid derivative having two substituents on its benzene ring, wherein the derivative has L-glutamate uptake inhibitory effect. More specifically, the present invention provides a compound of Formula (1) having an inhibitory effect against the glutamate uptake activity of L-glutamate transporters (wherein R1 represents an optionally substituted aromatic group, and substituent R2 represents a group selected from an optionally substituted linear or branched C1-C30 aliphatic group whose chain may contain nitrogen or oxygen, and an optionally substituted aromatic group) or a salt thereof, and a method for obtaining the above compound, as well as a method for purifying or detecting L-glutamate transporters using the above compound.