Application of gel‐phase ¹⁹F NMR spectroscopy for optimization of solid‐phase synthesis of a hydrophobic peptide from the signal sequence of the mucin MUC1

Abstract

This paper describes the manual Fmoc/t-Bu solid-phase synthesis of a difficult nine-residue hydrophobic peptide LLLLTVLTV from one of the signal sequences that flank the tandem repeat of the mucin MUC1. Gel-phase 19F NMR spectroscopy was used as a straightforward method for optimization of the solid-phase synthesis. Different approaches were applied for comparative studies. The strategy based on modified solid-phase conditions using DIC/HOAt for coupling, DBU for Fmoc deprotection, and the incorporation of the pseudo proline dipeptide Fmoc-Leu-Thr(psiMe, Me pro)-OH as a backbone-protecting group was found to be superior according to gel-phase 19F NMR spectroscopy. Implementation of the optimized Fmoc protocol enabled an effective synthesis of signal peptide LLLLTVLTV.

Porous polymer particles—A comprehensive guide to synthesis, characterization, functionalization and applications

“…As a complementary method to IR, Raman spectroscopy can reveal other functional groups (such as C-Cl and C≡N) that can be difficult to detect by IR [302][303]. Moreover, solid state [304][305], gel phase [306][307] and high-resolution magic angle spinning (HRMAS) NMR [308][309][310][311] techniques can be quite successfully applied to detect the functional groups and monitor reactions on particles. Availability of probes, operator experience and need of a suitable solvent for the analysis can be the parameters to tackle.…”

Improved Fmoc‐based solid‐phase synthesis of homologous peptide fragments of human and mouse prion proteins

“…Peptide sequences that present this problem have been commonly known as difficult sequences 3. One cause of these undesired synthetic problems is the self‐association of the growing peptide chain in β‐sheets4–7.…”

Synthesis and application of N‐[1‐(4‐(4‐fluorophenyl)‐2,6‐dioxocyclohexylidene)ethyl] (Fde)‐protected amino acids for optimization of solid‐phase peptide synthesis using gel‐phase 19F NMR spectroscopy

“…To fully evaluate the scope of Fde protection in solid-phase peptide synthesis, the hydrophobic peptide LLLLTVLTV 16 derived from the signal sequence from the mucin MUC1 was prepared. The synthesis of this difficult peptide has previously been optimized using gel-phase 19 F NMR spectroscopy as an analytical tool [10]. The optimization resulted in a modified Fmoc protocol using HOAt and DIC for amino acid couplings and 2% DBU in DMF for Fmoc removal.…”

“…Fluorinated linkers and building blocks, and fluorinated protective groups allow quantitative and qualitative analysis of the reaction outcome. Not long ago, we used this analytical tool to optimize the solid-phase synthesis of a 'difficult' nine-residue hydrophobic peptide LLLLTVLTV [10], which is a part of the signal sequence from the mucin MUC1 [11]. The optimization resulted in a modified Fmoc protocol based on HOAt and DIC for amino acid couplings and 2% DBU in DMF for Fmoc removal.…”