1. Contribution from the Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan, Chemical Analysis Center, Chiba University, 1-33 Yayoicho, Inageku, Chiba 263, Japan, and Department of Chemistry, University of Oldenburg, P.O. Box 2503, 26111 Oldenburg, Germany