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Synthesis of an Ellagitannin Component, the Macaranoyl Group with a Tetra-ortho-Substituted Diaryl Ether Structure
Hajime Hashimoto1, Takayuki Ishimoto1, Hayato Konishi1
1School of Science and Technology, Kwansei Gakuin University, 2-1 Gakuen, Sanda, Hyogo 669-1337, Japan.
Abstract:
Herein, a practical synthesis of the macaranoyl group contained in ellagitannins, i.e., a C-O digallate structure with a tetra-ortho-substituted diaryl ether bond, is described. The methodology involved an oxa-Michael addition/elimination reaction between a brominated ortho-quinone monoketal and a phenol with a hexahydroxydiphenoyl moiety in the presence of 18-crown-6 under dark conditions, followed by reductive aromatization. The existence of rotamers originating from the constructed ether moiety is discussed as well.
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