Selective Synthesis of Amino Acid Conjugates of Glycyrrhizic Acid Using N-Oxyphthalimide and N,N′-Dicyclohexylcarbodiimide

A selective synthesis of amino acid conjugates of glycyrrhizic acid containing amino acid residues in the carbohydrate part of the glycoside was proposed using N-oxyphthalimide (HOPt) and N,N′-dicyclohexylcarbodiimide (DCC), tert-butyl and benzyl/4-nitrobenzyl esters of L-amino acids with yields of 55–60%. Free conjugates of glycyrrhizic acid with valine, isoleucine, methionine, phenylalanine, leucine, tyrosine and glutamic acid were obtained by deblocking the ester groups.