1. Graduate School of Engineering Sciences, Kyushu University, 6-1, Kasuga-koh-en, Kasuga-shi, Fukuoka 816, Japan, and Institute of Advanced Material Study, Kyushu University, Fukuoka 816, Japan, and Lab. de Quimica Farmaceutica, Faculdade de Farmacia, Universidade de Coimbra, 3000 Coimbra, Portugal