Patent ID: 7723082

Claim:
A method for synthesizing a diketopiperazine derivative substituted in the 3- and 6-positions with amino acid-derived side chains, wherein the amino acid-derived side chains are from L-form of amino acids provided that said amino acid is not a proline or any alkylated amino acid residue, comprising the steps of: (1) transforming a biological system selected from the group consisting of a prokaryote and a non-human eukaryote host cell with a vector comprising a polynucleotide consisting of SEQ ID NO:3 (AlbC), and incubating said biological system under suitable culture conditions; (2) allowing the polynucleotide consisting of SEQ ID NO:3 to express AlbC peptide in the biological system and allowing the AlbC peptide to catalyze the cyclization of two amino acids, which are neither a proline nor an N-alkylated amino acid residue, so as to form a diketopiperazine derivative substituted in the 3- and 6-positions with said amino acid-derived side chains; and (3) recovering the diketopiperazine derivative substituted in the 3- and 6-positions with said amino acid-derived side chains thus obtained.