1. Department of Chemistry and Medical Chemistry, College of Science and Technology, Yonsei University, Wonju, Gangwondo 220‐710, South Korea, Fax: +82‐33‐760‐2956, http://nbml.yonsei.ac.kr
2. Department of Chemistry, Kyungpook National University, Taegu 702‐701, South Korea, Fax: +82‐53‐950‐6330