1. Lead Generation Research Laboratory, Tanabe Seiyaku Co., Ltd, 16–89, Kashima‐3‐chome, Yodogawa‐ku, Osaka 532, Japan.,
2. Pharmaceutical Development Research Laboratory, Tanabe Seiyaku Co., Ltd, 16–89, Kashima‐3‐chome, Yodogawa‐ku, Osaka 532, Japan.