1. Institut de Chimie des Substances Naturelles, CNRS, Avenue de la Terrasse, 91198 Gif‐sur‐Yvette, France, Fax: +33‐1‐69‐07‐72‐47
2. Current address: Sanofi‐Aventis, Sanofi‐Synthelabo Recherche, Isotope Chemistry and Metabolite Synthesis, 1 Avenue Pierre Brossolette, 91835 Chilly Mazarin, France