1. Graduate School of Pharmaceutical Sciences, Kyoto University, Yoshida, Sakyo, Kyoto 606-8501, Japan, Department of Pharmaceutical Chemistry, Faculty of Pharmacy, University of Khartoum, El Qasr Avenue, P. O. Box 1996, Khartoum 11111, Sudan, and Faculty of Pharmaceutical Sciences, Doshisha Women’s College of Liberal Arts, Kodo, Kyotanabe 610-0395, Japan