Simple methodology for the purification of amino acids

摘要

Amino acids are among the most important substances for life and are present in all living organisms. They are the basic constituents of proteins, which participate in a large number of biochemical processes. Indeed, with the completion of the human genome sequence, the next major scientific goal is the determination of the structure and function of all proteins of biological relevance. This effort requires, among others things, the specific preparation of both natural and unnatural amino acids, as well as their coupling in the synthesis of model peptides and proteins and remarkable activity is presently under way in this area. In this context, the synthesis and purification of amino acids continues to present a significant challenge to synthetic chemists. While ionic exchange resins are still one of the most reliable techniques especially for large-scale preparations, on occasion polar contaminants in reaction mixtures may cause interference that complicates the detection and purification (impurities may go unnoticed). Indeed, adsorption of the amino acid to the resin may be quite strong, leading to low yields. Because of these drawbacks, alternative processes are being developed. For the analytical detection of amino acids, silica gel thin-layer chromatography with propanol-aqueous ammonia as eluent has been described. We now report that adaptation of this technique turns out to be equally efficient for the isolation and separation of amino acids on a preparative scale. Furthermore, the implementation of this simple methodology allows not only the isolation, but also the separation of amino acids mixtures in high purity and good recovery. These results compare favorably with the use of ion-exchange resins and represent practical proceudres for the work-up of these substances.