S-Protected Cysteine Sulfoxide-Enabled Tryptophan-Selective Modification with Application to Peptide Lipidation

Lipidation of peptides is a promising means of modification that can improve the therapeutic character of biologically active peptides. Here, a novel lipidation protocol for peptides is described. The C–H sulfenylation of indole in peptides using S-p-methoxybenzyl cysteine sulfoxide under acidic conditions in the presence of ammonium chloride, anisole, and triisopropylsilane enables late-stage tryptophan-selective peptide lipidation. This developed protocol has been used successfully for the lipidation of glucagon-like peptides. Oral glucose tolerance tests in wild-type mice indicated that the resulting lipidated peptides stimulate insulin secretion and exhibit a more long-lasting blood-glucose-lowering effect than a parent nonlipidated peptide.