Synthetic Study of Carthamin: Biomimetic Synthesis of Carthamin Model via Peroxidase‐Catalyzed Oxidative Decarboxylation of Its Precursor Model

Abstract

A chiral carthamin model (3S,3′S)‐1‐[5‐acetyl‐2,6‐diketo‐3‐C‐β‐d‐glucopyranosylcyclohex‐4‐enylidene]‐1′‐[5′‐acetyl‐3′‐C‐β‐d‐glucopyranosyl‐2′,3′,4′‐trihydroxy‐6′‐oxocyclohexa‐1′,4′‐dienyl]methane, in which two cinnamoyl groups were replaced by an acetyl group, was synthesized by the dimerization of (S)‐2‐acetyl‐4‐C‐(per‐O‐acetyl‐β‐d‐glucopyranosyl)cyclohexadienone with glyoxylic acid, followed by peroxidase‐catalyzed oxidative decarboxylation and de‐O‐acetylation, or de‐O‐acetylation and peroxidase‐catalyzed oxidative decarboxylation. The corresponding total yields were 12.5% or 17.1% from 3‐C‐(per‐O‐acetyl‐β‐d‐glucopyranosyl)phloroacetophenone, and the reaction pathway was identical to the biosynthetic pathway.