SYNTHESIS OF PEPTIDES USING FREE AMINO-ACIDS - THE EFFECT OF INORGANIC-COMPOUNDS ON THE SOLUBILITY OF AMINO-ACIDS IN APROTIC-SOLVENTS

In order to increase the solubility of free amino acids so that they c ould be used in peptide synthesis, a system consisting of dimethylform amide, an inorganic additive, and pyridine was suggested. Compounds BF 3, AlCl3, SnCl2, SiCl4, ZnCl2, SbCl3, CaCl2, BaI2, CdI2, and NaI can s erve as the additives. Acylation of amino acids in such a solution (pH 5.2-5.3) with pentafluorophenyl esters of N-alpha-protected amino aci ds gave N-alpha-protected di- and tripeptides in a yield of more than 90%.