Selective Hydroxymethylation of Emodin

Abstract Electrochemical oxidation of 1,3,8-trihydroxy-6-methylanthraquinone, emodin, in dry alkaline methanol under a constant current of 0.05 A for 10 h under an applied potential difference of 15 V at room temperature resulted, for the first time, in an efficient and selective hydroxymethylation at C-2. The structure of the product was established from the detailed spectral analyses of its trimethyl ether and tetraacetylated derivative.