Amavadin, an Example for Selective Binding of Vanadium in Nature: Studies of Its Complexation Chemistry and a New Structural Proposal

The selective enrichment of metals in nature is of great interest.[1] For example, the concentration of vanadium in the blood of tunicates is a millionfold higher than in sea water.[2–4] Fly agaric (Amanita muscaria) also concentrates vanadium.[5,6]The structure of the vanadium compound of tunicates has not yet been elucidated.[7,8] However, a structure (3) has been proposed[9] for the vanadium compound of fly agaric, amavadin.[9‐11] The structural elucidation and synthesis of the organic ligand 1b[9b] allows, for the first time, the specificity of a naturally occurring vanadium ligand to be investigated. Amavadin can be prepared from VIVO salts and synthetic 1b.[9b] Since the ligand 1b was previously unknown and since all attempts to obtain crystals of amavadin suitable for an X‐ray structure analysis failed, a detailed investigation of the complex formation of 1b should also provide an answer to the question of the arrangement of the ligands around the central atom in amavadin.