1. Marine Biodiscovery Centre, Department of Chemistry, University of Aberdeen, Meston Walk, Aberdeen AB24 3UE, Scotland, U.K., Institute of Medical Sciences, University of Aberdeen, Ashgrove Road West, Aberdeen AB25 2ZD, Scotland, U.K., Laboratoire de Biologie Moléculaire et Cellulaire du Cancer, Hôpital Kirchberg, 9 Rue Edward Steichen, L-2540 Luxembourg, Luxembourg, and Department of Chemistry, University of Aberdeen, Meston Walk, Aberdeen AB24 3UE, Scotland, U.K.