1. NMR Research Unit University of Oulu P.O. Box 3000 90014 Oulu Finland
2. Department of Chemistry University of Helsinki A. I. Virtasen aukio 1 00014 Helsinki Finland
3. Present address: Discovery, Product Development & Supply (DPDS) Janssen Pharmaceutical Companies of Johnson & Johnson Turnhoutseweg 30 2340 Beerse Belgium