1. Howard Hughes Medical Institute, Beckman Center, B159, Stanford University Medical Center, CA 94305, U.S.A.
2. Department of Exploratory Medicinal Chemistry, Central Research Division, Pfizer Inc., Groton, CT 06340, U.S.A.
3. Laboratory of Molecular Endocrinology, University Department of Clinical Biochemistry, Rigshospitalet 6321, Copenhagen DK-2100, Denmark