1. Division of Medicinal & Natural Products Chemistry, The University of Iowa, Iowa City, Iowa 52242, Laboratory for the Structure of Matter, Code 6030, Clinical Psychopharmacology Section, IRP, NIDA, NIH, DHHS, Baltimore, Maryland 21224, Naval Research Laboratory, 4555 Overlook Avenue, SW, Washington, D.C. 20735, and University of Iowa High Field NMR Facility, Iowa City, Iowa 52242