New method of preparation of carboxy-protected amino acid conjugates of glycyrrhizinic acid.

A method for preparation of carboxy-protected amino acid conjugates of glycyrrhizinic acid with the use of -hydroxybenzotriazole, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, and methyl esters of L-amino acids (phenylalanine, tyrosine, leucine, isoleucine, and methionine) in 85-90% yield was developed. The structure of the prepared compounds was confirmed by IR and C NMR spectra.

Glycyrrhizic acid derivatives as influenza A/H1N1 virus inhibitors.

This Letter describes the synthesis and antiviral activity study of some glycyrrhizic acid (GL) derivatives against influenza A/H1N1/pdm09 virus in MDCK cells. Conjugation of GL with l-amino acids or their methyl esters, and amino sugar (d-galactose amine) dramatically changed its activity. The most active compounds were GL conjugates with aromatic amino acids methyl esters (phenylalanine and tyrosine) (SI=61 and 38), and S-benzyl-cysteine (SI=71).

Synthesis of amino acid conjugates of glycyrrhizic acid using -hydroxyphthalimide and ,'-dicyclohexylcarbodiimide.

Synthesis of amino acid conjugates of glycyrrhizic acid with the use of -hydroxyphthalimide, ,'-dicyclohexylcarbodiimide, and -butyl esters of L-amino acids (valine, isoleucine, phenylalanine, and methionine) was performed followed by deprotection with trifluoroacetic acid. The target amino acid conjugates were isolated by column chromatography on silica gel in 40-45% yield. The structure of the prepared compounds was confirmed by IR and C NMR spectroscopy.