The invention provides dicarboxylic acid-substituted heteroaryl derivatives of the formula G1-R2)n-Q1-B-Q2-R4)m-G2I or a pharmaceutically acceptable salt thereof, wherein G1, G2, R1, R2, R3, R4, n, m, Q1, Q2, and B are as defined in the specification. The rotational angle measurement apparatus includes a magnetic sensor 301 and a signal processing unit 303M. An input signal is received at a selected connection node of the connection nodes.