Efficient Solid-Phase Synthesis of Sulfotyrosine Peptides using a Sulfate Protecting-Group Strategy

Chemical Methods for N- and O-Sulfation of Small Molecules, Amino Acids and Peptides

Sulfation of the amino acid residues of proteins is a significant post-translational modification, the functions of which are yet to be fully understood. Current sulfation methods are limited mainly to O-tyrosine (sY), which requires negatively charged species around the desired amino acid residue and a specific sulfotransferase enzyme. Alternatively, for solid-phase peptide synthesis, a de novo protected sY is required. Therefore, synthetic routes that go beyond O-sulfation are required. We have developed a novel route to N-sulfamation and can dial-in/out O-sulfation (without S-sulfurothiolation), mimicking the initiation step of the ping-pong sulfation mechanism identified in structural biology. This rapid, low-temperature and non-racemising method is applicable to a range of amines, amides, amino acids, and peptide sequences.

Synthesis of Sulfotyrosine-Containing Peptides by Incorporating Fluorosulfated Tyrosine Using an Fmoc-Based Solid-Phase Strategy

Tyrosine O-sulfation is a common protein post-translational modification that regulates many biological processes, including leukocyte adhesion and chemotaxis. Many peptides with therapeutic potential contain one or more sulfotyrosine residues. We report a one-step synthesis for Fmoc-fluorosulfated tyrosine. An efficient Fmoc-based solid-phase peptide synthetic strategy is then introduced for incorporating the fluorosulfated tyrosine residue into peptides of interest. Standard simultaneous peptide-resin cleavage and removal of the acid-labile side-chain protecting groups affords the crude peptides containing fluorosulfated tyrosine. Basic ethylene glycol, serving both as solvent and reactant, transforms the fluorosulfated tyrosine peptides into sulfotyrosine peptides in high yield.