Chemical-structural study on a blue metal-complex pigment of hydrangea by using synthetic 5-O-acylquinic acids

DOI

Bibliographic Information

Other Title
  • 5-O-アシル化キナ酸類の効率的合成によるアジサイの 青色金属錯体色素の化学構造研究

Description

<p>Blue sepal-color of Hydragea macrophylla is due to a metal-complex pigment composed with delphinidin 3-glucoside (1), 5-O-caffeoylquininc acid (2) and/or 5-O-p-coumaroylquinic acid (3) as co-pigments, and Al3+ in an aqueous solution around pH 4.0. However, the structure of the hydrangea-blue complex is still remained obscure. To obtain the structural information of hydrangea-blue complex, we developed an efficient synthetic method of 5-O-acylquinic acids and then carried out spectroscopy studies. For synthesis of 5-O-acylquinic acids, we designed p-methoxybenzyl quinate as a key intermediate. Next, the esterification of the sterically hindered 5-OH group were realized by using improved Tanabe’s method (TsCl/NMI/i-Pr2NEt). For the final deprotection step, we established a TFA- or BCl3/C6HMe5-catalyzed method. 5-O-Acylquinic acids were synthesized in seven steps with 45-60% overall yield. The Vis, CD, and 1H-NMR spectroscopy studies of the reconstructed hydrangea-blue complex were performed by using the synthetic 5-O-acylquinic acids. In highly concentrated acetate buffer (6 M, pH 4.0), we could measure 1H NMR of both the hydrangea-blue complex composed of 1 (5 mM), 2 (10 mM), and Al3+ (10 mM) and a simple 1−Al3+complex. Comparison of those 1H NMR signals indicated that in the hydrangea-blue complex 1 might be under equilibrium between chelating and nonchelating structures having an interaction with 2.</p>

Journal

Details 詳細情報について

  • CRID
    1390001288074203648
  • NII Article ID
    130007494868
  • DOI
    10.24496/tennenyuki.57.0_posterp61
  • ISSN
    24331856
  • Text Lang
    ja
  • Data Source
    • JaLC
    • CiNii Articles
  • Abstract License Flag
    Disallowed

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