Use of Marfeyʹs reagent and analogs for chiral amino acid analysis: Assessment and applications to natural products and biological systems

The present paper describes an updated knowledge and status on Marfeyʹs reagent (MR), 1-fluoro-2,4-dinitrophenyl-5-l-alanine amide (FDNP-l-Ala-NH2). The reagent is used for pre-column derivatization of amino acids followed by HPLC separation of the diastereomers so formed. Emphasis is put on the design and application of structural variants which are synthesized by introducing different (other than l-Ala-NH2) l- and d-amino acid amides and amino acids in the 1,5-difluoro-2,4-dinitro benzene (DFDNB) moiety, as the chiral auxiliary. Advantages, disadvantages, the required precautions and suitability of the approach for the separation of multi component mixtures of dl-amino acids are assessed. Use of two dimensional (2D) techniques, in particular online HPLC in combination with various mass spectrometry techniques is discussed as well as methods designated ‘advanced Marfeyʹs method’ and ‘C3 Marfeyʹs method’. Application of MR and its variants for the determination of the stereochemistry of protein and non-protein amino acids in bioactive natural products isolated from living organisms (bacteria including blue-green algae, filamentous fungi, plants, marine sponges, invertebrates and vertebrates), in physiological samples including human beings, and in biologically relevant synthetic peptides are presented. In an outlook future applications are envisaged.