Studies On The Process Of The Self-Assembly Of Amino Acids Mediated By Phosphorus Chloride By ～(31)P NMR And ESI-MS/MS

Penta-coordinated phosphorus compounds are very important in organic phosphorus chemistry and biological chemistry. After W-phospho-a-amino acids are obtained by the phosphorylation of amino acids, they could take place many kinds of bioorganic reactions in water-alcohol media. For example, peptide formation, the ester formation, the ester exchange on phosphorus and N-O phosphoryl migration reactions were all observed. These reactions involved penta-coordinated phosphorus amino acids intermediates. The peptide formation is one of the most important reactions in prebiotic evolution. The peptide formation reaction of W-phosphoryl amino acids is a significant part of the model about the origin of life, "Co-evolution of proteins and nucleotides from N-phosphoryl amino acids". Therefore, it is very important for comprehending the process of biochemistry and the origin of life to study the peptide formation reactions of penta-coordinated phosphoryl amino acids and the self-assembly of a-amino acids .In this thesis ,the processes of the self-assembly into peptides of amino acids mediated by phosphorus pentachloride,phosphorus oxychloride and phosphrus trichloride were detailedly studied by 31P NMR and ESI-MS techniques. The results are illustrated as follows:L-or-amino acids or D-a-amino acids could be phosphorylated by phosphorus pentachloride, phosphorus oxychloride and phosphrus trichloride respectively first, then assembled into oligo-peptides. As reaction time was prolonged, the lengths of the peptides were increased. For example,L-Ala and L-Val could be assembled into decpeptide ,while L-Gly, L-His and L-Phe could only be assembled into dipeptide and tripeptide. D-Ala and L-Ala gave similar results, while the assembly of the racemic mixed DL-amino acids were not so effective as the chirality pure one. Under the same conditions, the p-amino acids could not be assembled into peptides.Under the acid conditions, the mechanisms of the self-assembly into peptides ofamino acids mediated by phosphorus pentachloride, phosphorus oxychloride and phosphrus trichloride are different, while amino acids mediated by phosphrus chloride maybe all form cyclic penta-coordinated phosphrus intermediate first,which could be attacked by oxygen atoms on carboxylic group of amino acids and formed N-phosphoryl amino acid-amino acid anhydrides. The cyclic phosphoryl amino acids were found in the reaction mixture by ESI-MS technique.Similarly, under basic conditions or in non-protonic solvent, N,O-bis(trimethylsilyl)amino acids could be assembled into oligo-peptides mediated by phosphorus chloride. Three steps were involved in the self-organization reactions,i.e. the activation of amino acids, the elongation of peptide chain and the termination of the chain reaction, among which the activation of amino acid was the key step. The amino acid pentacoordinated phosphorus compounds, formed by the reaction of N,O-bis(trimethylsilyl)amino acids with phosphorus chloride at room temperature in anhydrous dichloromethane,could be found by 31P NMR technique. In addition ,the cyclic and spiro amino acid penta-coordinated phosphorus intermedate could be found in 31P NMR spectra when the ammount of N,O-bis(trimethylsilyl)amino acids were inadequate. The spiro amino acid penta-coordinated phosophorus intermedate were stable.The oligo-peptide methyl esters were proved by ESI-MS/MS, which showed that the C-N bonds were the easiest ruptures in oligo-peptides molecules. The polypeptide methyl esters were protonated at the ester group, and the fragmentation started on the carboxyl terminal of oligo-peptides methyl ester in ESI-MS/MS.The self-assembly into peptides of amino acids mediated by phosphorus is possessed by the chiral selectivity. The steric configuration matched between the phosphoryl amino acids and the same chiral amino acids, therefore, the phosphoryl amino acids would like to react with the same chiral amino acids and to form peptides. On the contrary, they would hardly react with the opposite chiral amino acids as the steric...