Miyazawa T, Otomatsu T, Yamada T, Kuwata S. Racemization studies in peptide synthesis through the separation of protected epimeric peptides by reversed-phase high performance liquid chromatography.
INTERNATIONAL JOURNAL OF PEPTIDE AND PROTEIN RESEARCH 1992;
39:229-36. [PMID:
1399262 DOI:
10.1111/j.1399-3011.1992.tb00794.x]
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Abstract
Separation of protected epimeric peptides, Z-Gly-Xaa-Xbb-OMe (where Xaa and Xbb = chiral amino acid residues), by reversed-phase HPLC was utilized for studying racemization in peptide synthesis. Thus, the following factors which might affect the extent of racemization during the coupling by the carbodiimide method were investigated: the combination of amino acid residues to be coupled, coexisting tertiary amine salts, and the relative configuration of the amino acid residues. The following points were revealed: the combination of bulky residues at the coupling site results in extensive racemization in a polar solvent such as DMF, the amine hydrochlorides cause less racemization than the p-toluene-sulfonates in DMF, and the influence of relative configuration differs depending on the solvent and the individuality of the amino components. Furthermore, the racemization-suppressing effect of some additives in the carbodiimide method was reevaluated by employing the same procedure.
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