Cyclodopa glucoside ( = (2S)‐5‐(β‐D‐glocopyranosyloxy)‐6‐hydroxyindoline‐2‐carboxylic acid) and its occurrence in red beet (beta vulgaris var. rubra L.)

Abstract

<jats:title>Abstract</jats:title><jats:p>Cyclodopa glucoside ( = (2<jats:italic>S</jats:italic>)‐5‐(β‐<jats:sc>D</jats:sc>‐glucopyranosyloxy)‐6‐hydroxyindoline‐2‐carboxylicacid; <jats:bold>1a</jats:bold>) is prepared from betainin (<jats:bold>2a</jats:bold>) <jats:italic>via</jats:italic> a base exchange reaction. Its purification and physical properties are described. The compound is <jats:italic>N</jats:italic>‐formylated in dilute HCOOH solution. Cyclodopa glucoside is contained in considerable amount in redbeet juice varying from 0.07 to 1.9 mmol/kg or from 12 to 46% relative to teh content of betanin. Teh occurrence of free cyclodopa glucoside supports its role as intermediate in betanin biosynthesis.