Trichloroethyl Group As a Protecting Group for Sulfonates and Its Application to the Synthesis of a Disulfonate Analog of the Tyrosine Sulfated PSGL-1₄₃₋₅₀ Peptide

The trichloroethyl (TCE) group is shown to be a viable protecting group for sulfonates. TCE-protected sulfonates were found to be particularly stable to acid, a key characteristic that led to a straightforward enantioselective synthesis of l-FmocPhe(p-CH₂SO₃TCE)OH. This was used as a building block for the solid phase synthesis of an octapeptide corresponding to P-selectin glycoprotein ligand-1 residues 43−50 (PSGL-1₄₃₋₅₀) in which sulfotyrosine residues 46 and 48 were replaced with (sulfonomethyl)phenylalanine (SmP), an important hydrolytically stable sulfotyrosine mimic.