1. Department of Chemistry, Pukyong National University, Busan 608-737, Korea, College of Chemistry & Chemical Engineering, Ocean University of China, Qingdao 266003, People's Republic of China, Drug Discovery and Design Centre, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, People's Republic of China, College of Pharmacy, Pusan National University, Busan 609-735, Korea, and Department of Chemistry, Dongeui University, Busan 614-714, Korea