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.

807leaves little doubt that the acylated phenylisoserine side chain of these taxoids is synthesized via path a of Scheme I. Unexpectedly, in both experiments 1, but not 2, also showed a pronounced M + 10 peak, as well as a P + 10 satellite for the m / z 286 fragment representing the side chain. Hence, the aromatic ring of 4a and Sa must have also becn incorporated into the benzoyl group of the 1 side chain. Together with the non-incorporation of 7a this suggests the operation of a new pathway, other than the estab-lishedI3 path b/c of Scheme I, for the genesis of the benzoate moieties in this plant which proceeds from 3 via 4 (path a/d) or 4 and S (path a/e).In summary, the side chain of 1 and 2 is formed from phenylalanine via @-phenylalanine, presumably generated by an aminomutase reaction,14 followed by hydroxylation of C-2 and acylation of the nitrogen. The benzoyl moiety is also formed via @-phenylalanine and possibly phenylisoserine rather than via cinnamic acid. A&"t .We are indebted to Prof.

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9PL[M~v(hidpa)~]-[hidpas-= (oxyimino)dipropionate(3-)] has been synthesised and shown to possess the novel, octacoordinated structure identified for Amavadin, the form in which vanadium(iv) is bound in Amanita muscaria mushrooms; [Mov(hidpaj2]-is capable of both a one-electron reduction and a one-electron oxidation.

Discrete variational Xa (DVXa) calculations have been carried out for the eight-co-ordinated vanadium-( iv) and -(v) complexes [V(hida)2]z--11-(H,hida = Nhydroxyiminodiacetic acid). These complexes are

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