1. Contribution from the Department of Pharmaceutical Chemistry, University of California, San Francisco, Mission Bay Genentech Hall, 600 16th Street, Mail Box 2240, San Francisco, California 94143, Dipartimento di Chimica, Universitá degli studi di Modena e Reggio Emilia, via Campi 183, Modena, Italy, Department of Molecular Pharmacology and Biological Chemistry, Northwestern University, 303 East Chicago Avenue, Chicago, Illinois 60611, and Servicio de Microbiologia, Hospital Ramón y Cajal, National...