Electrochemical synthesis of L-histidinol using solvated electrons

The feasibility the preparation of L-histidinol (I) by reduction of L-histidine methyl ester (II) using an electrogenerated solvated electrons solution has been studied in a laboratory scale reactor. The solvated electrons solution was obtained by electrolysis of a solution of LiCl in EtNH2 that permits an easier handling than NH3 or MeNH3. All components of the electrochemical setup have been optimized for the reaction conditions used. The influence of some reaction variables on the yield of (I) has been studied. Thus, increasing current intensity and temperature enhances the yield of L-histidinol. Nevertheless, the volatility of ethylamine limits the increase of the intensity current and the temperature. A fractionated feeding procedure of (II) was shown to be desirable. The work-up and isolation procedure of (I) has also been described. It includes an electrodialysis process that makes easier the isolation of (I), as well as the recovered LiCl could be recycled as supporting electrolyte. (c) 2005 The Electrochemical Society. All rights reserved.