1. Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyoto 615-8510, Japan
2. CREST, JST, Kyoto 615-8510, Japan
3. Research Division, Nihon Nohyaku Company, Ltd., Osaka 586-0094, Japan
4. Department of Biological Chemistry, Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto 606-8501, Japan