1. Contribution from the Faculty of Pharmaceutical Sciences, The University of Tokushima, Sho-machi, Tokushima 770, Japan, Institute for Medical Research, Wakunaga Pharmaceutical Co., Ltd., 1624 Shimokotachi, Koda-cho, Takata-gun, Hiroshima 739-11, Japan, Faculty of Engineering, The Shinshu University, 500 Wakazato, Nagano 380, Japan, Kissei Pharmaceutical Co., Ltd., 4365-1 Kashiwabara, Hotaka, Minamiazumi-gun, Nagano 399-83, Japan, and Rigaku Corporation, 3-9-12 Matubara-cho, Akishima, Tokyo 196, Japan