Stereospecificity of peptide synthesis by means of phosphorus derivatives: a model of peptide synthesis in molecular evolution |
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Authors: | Hans R. Kricheldorf Thomas Mang |
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Affiliation: | Institut für Angewandte Chemie der Universität, Martin-Luther-King-Platz 6, D-2000 Hamburg 13, FRG |
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Abstract: | A hypothesis is presented to explain the prebiotic formation of optically pure oligo- and polypeptides from racemic amino acids. Stereospecific condensation reactions favouring the formation of isotactic stereosequences (l-l and d-d blocks) are a basic requirement of this hypothesis. Since phosphorus derivatives such as polyphosphates or nucleic acid imidazolides were postulated to be prebiotic condensing reagents, a variety of peptide syntheses by means of phosphorus derivatives was investigated. Dipeptides and tripeptides were prepared from N-protected d,l-amino acids or d,l-amino acid esters, and d,l-leucine and d,l-valine were subjected to condensation polymerizations. The stereosequences were analysed by means of 13C n.m.r. spectroscopy. More than 80% of all condensations were more or less stereospecific and in all cases isotactic sequences were predominant. In the case of poly(d,l-leucines), 13C n.m.r. cross-polarization/magic angle spinning (CP/MAS) spectra revealed the formation of α-helical blocks. |
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Keywords: | Polypeptides stereospecificity peptide synthesis evolution |
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