1. Leiden Institute of Chemistry, Gorlaeus Laboratories, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands, Faculty of Pharmaceutical Sciences, University of Tokushima, Shomachi, Tokushima 770-8505, Japan, Graduate School of Material Science, Himeji Institute of Technology, University of Hyogo, Kohto, Kamigori, Hyogo 678-1297, Japan, and Laboratory of Organic Chemistry, Wageningen University, Dreijenplein 8, 6703 HG Wageningen, The Netherlands