1. Chugoku Kayaku Co., Ltd., Etajima-cho, Aki-gun, Hiroshima 737-21, Japan
2. Department of Chemistry, Faculty of Science, Hiroshima University, Kagamiyama, 1-3-1, Higashi Hiroshima-City 724, Japan
3. Department of Chemistry, Faculty of Science, Hiroshima University, Kagamiyama, 1-3-1, Higashi Hiroshima-City 724, Japan, and PRESTO, Research Development Corporation of Japan, Research Consortium, Tsukuba 300-26, Japan