A compound represented by the formula (I) [at least one of R 1 , R 2 , and R 3 represents a cyclic alkyl group, the remaining represents a linear or branched alkyl group； n represents 0 or 1； R 4 represents an amino group or -(CX 2 ) m -COOH (m represents 0 to 3, and X represents hydrogen atom)； and R 5 represents -(CY 2 ) p -COOR 6 (p represents 0 to 3, Y represents hydrogen atom, and R 6 represents hydrogen atom or an alkyl group)], or a salt thereof.
