1. Contribution from the Faculty of Pharmaceutical Sciences, Kyushu University, Fukuoka 812-82, Institute for Fundamental Research in Organic Chemistry, Kyushu University, Fukuoka 812-81, Japan, and Institut de Physique et Chemie des Matériaux de Strasbourg, Unité Mixte CNRS-ULP-EHICS (UMR 046), 23 rue due Loess, F-67037 Strasbourg Cedex, France