1. Department of Natural Products Chemistry, Shenyang Pharmaceutical University, 103 Wenhua Road, Shenhe District Shenyang 110016, People's Republic of China, Department of Chemistry, College of Humanities and Sciences, Nihon University, Sakurajosui, Setagaya-ku, Tokyo 156-8550, Japan, and College of Pharmacy, Nihon University, 7-7-1 Narasinodai, Funabashi, Chiba 274-8555, Japan