1. Research Group for Alkaloid Chemistry, Hungarian Academy of Sciences, H‐1521 Budapest, POB 91 (Hungary)
2. Central Research Institute for Chemistry, Hungarian Academy of Sciences, H‐1525 Budapest, POB 14 (Hungary)
3. Lehrstuhl für Strukturchemie, Ruhruniversität Bochum, D‐4630 Bochum 1, POB 1021 48 (F. R. Germany)