ムギネ酸の構造と合成および金属錯体

概要

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Mugineic acid (1), an amino acid isolated from the roots of water-cultured barley (Hordeum vulgare L. var. Minorimugi), is the first phytosiderophore to be shown to play a role in the uptake and transport of iron in higher plants. The structure of 1 was determined as 2 (S), 2 (S), 3 (S), -3 (S) -N- [3-carboxy-3- (3-carboxy-3-hydroxypropylamino) -2-hydroxypropy1] -2-azetidine-2-carboxylic acid by a direct X-ray crystallographic method, and chemical and physico-chemical studies of the degradated products of 1. Structures of other analogous amino acids from some graminaceous plants were also elucidated. Stereospecific total syntheses of 2-deoxymugineic acid (9) and avenic acid A (11) were achieved by using common key intermediate 28 obtained from L-α-hydroxy-γ-butyrolactone (17) in short steps. N-Alkylation procedure by means of sodium cyanoborohydride in neutral media were effective for condensation of optically active units (e. g. 16c+24 25). The N, O-protecting groups were removed in two steps at the final stage of the synthesis. The structures and properties of metal complexes of mugineic acid were examined by X-ray crystallographic analysis, the potentiometric titration, spectroscopic, and electrochemical studies.
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