1. Contribution from the Department of Fundamental Science, Iwaki−Meisei University, Iwaki, Fukushima 970, Japan, Nicolet Japan Corporation, Hatsudai 2-5-8, Shibuya-ku, Tokyo 151, Japan, Laboratory of Pharmaceutical Chemistry, School of Pharmacy, Tokyo University of Pharmacy and Life Science, 1432-1 Horinouchi, Hachioji, Tokyo 192-03, Japan, and School of Biological Sciences, University of Missouri, Kansas City, Missouri 64110