1. Institute of Organic Chemistry, Justus-Liebig-Universität Giessen, Heinrich-Buff-Ring 58, 35390 Giessen, Germany, Department of Medicine and Department of Radiology, Division of Hematology/Oncology, Beth Israel Deaconess Medical Center, 330 Brookline Avenue, Boston, Massachusetts 02215, and MGI Pharma, 6611 Tributary Street, Baltimore, Maryland 21224