Synthesis and Antiviral Activity of Glycyrrhizic-Acid Conjugates with Aromatic Amino Acids

Amino-acid conjugates of glycyrrhizic acid (GA) containing phenylalanine, tyrosine, and tryptophan in the carbohydrate and triterpene parts were synthesized using N-hydroxybenzotriazole (HOBt)-N,N′-dicyclohexylcarbodiimide (DCC) and sodium salts of the amino acids. GA conjugates containing two aminoacid residues in the glycoside carbohydrate part were synthesized using N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline. The GA conjugate with tyrosine exhibited weak but consistent antiviral activity against flu virus A/St.-Petersburg/05/09 (H1N1)pdm09 that was similar to the standard strain A/California/07/09 and pronounced antiviral activity against respiratory-syncytial virus (RSV) and herpes simplex virus (HSV-1).