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The use of crown ethers in peptide chemistry

Hyde, Carolyn Barker; (1990) The use of crown ethers in peptide chemistry. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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Abstract

The formation of amino acid fatty esters using 18-Crown-6 is discussed and compared with previous methods. Initial results indicate that the method would be viable. Thus the use of the K+ salts of N-protected amino acids, 18-Crown-6 and the appropriate alkyl halide gives rise to the N-protected amino acid ester in moderate to good yield, providing there is no steric hindrance. The use of 18-Crown-6 as an N-terminal protecting group in peptide synthesis is studied. In solvents such as as MeCN or CHCl3, oligomerisation occurs. This is shown to be due to an intramolecular hydrogen bond between the NH3' group and the imine nitrogen of the O-acyl isourea derivative. The use of a dipeptide complex inhibits the formation of this hydrogen bond to a certain extent. Combining the use of a dipeptide complex with a polar solvent inhibits oligomerization but gives rise to unwanted amino acid derivatisation. There is reaction between the complex and the DMSO at the N-terminal end. The carboxylate ion group acts as catalyst in the reaction between DCC and DMSO to give an intermediate. The mechanism of this reaction is proposed. Substitution of DMF as solvent leads to suppression of both oligomerisation and derivatisation. Therefore, addition of a dipeptide complex and DCC solution to a solution containing: an amino acid ester and TEA at 0°C leads to peptide bond formation. Optimisation of the conditions is still required, however the synthesis of an Enkephalin derivative has been achieved.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: The use of crown ethers in peptide chemistry
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by ProQuest.
URI: https://discovery.ucl.ac.uk/id/eprint/10116701
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