The synthesis and spectroscopic analysis of the neurotoxic prion peptide 106-126: Comparative use of manual Boc and Fmoc chemistry

A peptide corresponding to residues 106-126 of the human prion protein (PrP) possesses the neurotoxic and amyloidogenic properties of the infectious form of the parental protein. This peptide is now identified as a 'difficult sequence' and synthesis using conventional manual Fmoc chemistry was unsuccessful with acylation terminating at a central core of hydrophobic amino acids. The use of tetramethylfluoroformamidinium hexafluorophosphate and 1-methyl-2- pyrrolidone as anti-aggregatory agents in the coupling steps improved the synthesis but still resulted in an incomplete peptide. The incorporation of N-(2-hydroxy-4-methoxybenzyl) protection at glycine residues 119 and 124 enabled synthesis of the full length peptide in low yield. Synthesis using Boc chemistry with in situ neutralisation gave the full length peptide in high yield.