1. Contribution from the Macrocyclics, 2110 Research Row, Suite 425, Dallas, Texas 75235, Department of Chemistry, University of Texas at Dallas, P.O. Box 803066, Richardson, Texas 75083, Dow Chemical Company, 2301 North Brazosport Boulevard, Freeport, Texas 77541, Department of Chemistry, University of Houston, 136 Fleming Building, Houston, Texas 77204-5003, Department of Chemistry, Rice University, P.O. Box 1892, Houston, 77251-1892, and Rogers Magnetic Resonance Center, Department of Radiology,...