1. Laboratory of Organic Chemistry, Wageningen University, Dreijenplein 8, 6703 HB Wageningen, The Netherlands (J.-W.d.K., M.C.R.F., M.J., A.d.G.); and
2. Plant Research International, P.O. Box 16, 6700 AA Wageningen, The Netherlands (J.-W.d.K., M.J., H.J.B.)