Use of Marfey's reagent to quantitate racemization upon anchoring of amino acids to solid supports for peptide synthesis.

A chromatographic assay has been developed to quantitate racemization occurring during attachment of protected amino acids to peptide synthesis resins. Acidolytic cleavage of deprotected amino acids from supports and subsequent derivatization with 1-fluoro-2,4-dinitrophenyl-5-L-alanine amide (Marfey's reagent) gave diastereomers separable by reverse-phase HPLC using aqueous acetonitrile. The assay is reliable to 0.1% racemate with a detection limit of approximately 100 pmol. The technique was applied to several acid-labile resins and was used to evaluate the racemizing characteristics of various anchoring methods.