3-​Benzofurancarboxylic acid, 4-​[(1E)​-​3-​[(1R)​-​1-​carboxy-​2-​(3,​4-​dihydroxyphenyl)​ethoxy]​-​3-​oxo-​1-​propen-​1-​yl]​-​2-​(3,​4-​dihydroxyphenyl)​-​2,​3-​dihydro-​7-​hydroxy-​, 3-​[(1R)​-​1-​[(3,​4-​dihydroxyphenyl)​methyl]​-​2-​methoxy-​2-​oxoe