The Structural Characterization of Amavadin

Abstract

Fly agaric accumulate vanadium in the form of amavadin, whose structure has been elucidated (see picture for the crystal structure). Amavadin contains one VIV center coordinated to two (S,S)‐hidpa3− ligands (H3hidpa=2,2′‐(hydroxyimino)dipropionic acid) through one η2‐NO− group and two unidentate carboxylato groups from each ligand. The arrangement of the two η2‐NO− groups leads to a chiral vanadium center, which has been characterized in both the Λ and Δ forms. The carboxylato groups of the amavadin anions bind cations, for example, Ca2+ ions, and/or become involved in hydrogen bonding.

Study on the isomerism in meso-amavadin and an amavadin analogue

“…2) is similar to that reported earlier for the Ca 2+ salt of the naturally occurring amavadin [7]. The four unidentate carboxylates constitute the equatorial VO 4 -plane and the two N-O groups bind side-on above and below the plane.…”

“…It has previously been demonstrated that the vanadium atom of amavadin is chiral and that the complex exists as D and K diastereomers [7]. 3 Furthermore, the vanadium atom is configurationally labile in solution and the complex is prone to epimerization [18,23,24].…”

“…5a) [18,23]. It has previously been shown that only minimal structural changes take place upon the one-electron oxidation to vanadium(V) when the amavadin ligand 1 [7,24] In 'meso-amavadin' the situation appeared to be more complicated because the presence of (R) and (S) stereogenic centers in the ligands breaks the symmetry of the molecule. This results in eight different possibilities to arrange the two meso-ligands around the vanadium, instead of the two possibilities for the (S,S)-ligands.…”

“…However, no X-ray structure could be obtained [5,6]. 1 It took until 1999 [7,8] for single crystal X-ray studies to be reported. firmed the 'bare' vanadium(IV) in an octa-coordinated complex (2).…”

DNA cleavage, binding and intercalation studies of drug-based oxovanadium(IV) complexes

“…Vanadium occurs as an "essential trace" element in diverse living forms [1][2][3][4][5][6]. It plays active roles in many enzymatic reactions such as halogenation of organic substrate [2,5,6] and fixation of nitrogen through an alternative pathway [2,[7][8][9].…”