1. Department of Applied Chemistry and Biotechnology, Graduate School of Engineering, Chiba University, 1‐33, Yayoi‐cho, Inage‐ku, Chiba 263‐8522, Japan, Fax: +81‐43‐290‐3401
2. MCC‐Group Science and Technology Reserch Center, Mitsubishi Chemical Corporation, 1000 Kamoshida, Aoba‐ku, Yokohama 277‐8522, Japan