1. Department of Chemistry, National Tsing Hua University, Hsinchu 300-71, Taiwan
2. Department of Chemistry, National Sun Yat-sen University, Kaohsiung 804, Taiwan
3. Department of Chemistry, National Taiwan Normal University, Taipei 106, Taiwan
4. Institute of Biological Chemistry, Academia Sinica, Taipei 115, Taiwan
5. Institute of Chemistry, Academia Sinica, Taipei 115, Taiwan
6. Department of Chemistry, National Taiwan University, Taipei 106, Taiwan