Tchertchian S, Hartley O, Botti P. Synthesis of Nα-(1-Phenyl-2-mercaptoethyl) Amino Acids, New Building Blocks for Ligation and Cyclization at Non-Cysteine Sites: Scope and Limitations in Peptide Synthesis.
J Org Chem 2004;
69:9208-14. [PMID:
15609957 DOI:
10.1021/jo049471k]
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Abstract
A new and convenient method for the synthesis and incorporation of N(alpha)-(1-phenyl-2-mercaptoethyl)-derivatized amino acids applicable to chemical ligation at non-cysteine sites is presented. N(alpha)-Auxiliary derivatives of glycine and alanine were easily prepared using reductive amination approaches. Several strategies for the incorporation of these derivatives into peptide chains were investigated: coupling without protection, with acid-labile protection, with base-labile protection, and via a novel protection strategy using the thiazolidine derivative. All amino acid derivatives were successfully coupled to various peptide resins, and with the exception of those incorporating Boc-protected derivatives, all resins yielded the desired peptide fragments. However, the coupling of the two alanine derivative diastereomers generated some epimerization. Finally, N-terminal auxiliary glycine and alanine peptides were cyclized, and the corresponding native circular peptides were obtained upon successful removal of the auxiliary.
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