Year: 2012
Type: conference-paper
Abstract: The chemical synthesis of polypeptides can be accomplished with a technique called Native Chemical Ligation (NCL), which requires two peptides, one with a C-terminal thioester and another one with an N-terminal cysteine. Conventional peptide thioester syntheses require coupling in the presence of organic bases, which can cause a serious epimerization problem, and consequently purification difficulties, as well as low reaction yields of the desired stereoisomer. There is a great need for alternative methods that avoid or minimize epimerization and preserve the chiral integrity of the C-terminal amino acid. The goal of this research is to demonstrate that a photochemical base-free acylation method developed in our laboratory generates only one stereoisomer of a peptide thioester. We have synthesized two dipeptides with the C-terminal amino acid phenylalanine in L- and D-configuration. In order to unambiguously show that the chirality of the C-terminal amino acid is the same before and after the photochemical thioester synthesis, diastereomeric dipeptides with the photoreactive nitroindoline moiety were synthesized and individually converted into their dipeptide thioesters with UV light. The extent of epimerization was determined by the ratio of the two diastereomeric dipeptide thioesters obtained, each of which has a distinct NMR spectrum. Our results show that chiral integrity is largely maintained in our novel photochemical acylation method.
Authors: Renato A Sousa, Andrew Pardo, Katja Michael
Language: English
Subfield: Molecular Biology
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W106988370