1. University of Bayreuth Bioorganic Chemistry Universitätsstraße 30 95447 Bayreuth Germany
2. Dpto. Química Orgánica I Fac. Ciencias Químicas Universidad Complutense de Madrid Avd. Complutense s/n 28040 Madrid Spain
3. Depts. of Molecular Medicine and Immunology and Microbiology The Scripps Research Institute 10550 N. Torrey Pines Road, La Jolla CA 92037 USA