A method for preparation of carboxy-protected amino acid conjugates of glycyrrhizinic acid with the use of N-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 (13)C NMR spectra.
New method of preparation of carboxy-protected amino acid conjugates of glycyrrhizinic acid