Extended Data Fig. 1: Surveying Wittig reagent reactivity with sulfenic acid.

Wittig reagents 1-7 were screened for reaction with the dipeptide-SOH model compound. Rate constants were obtained in acetonitrile(ACN):25 mM NaOAc (1:2 v/v) pH = 4.9. Isolation yields, literature (in parentheses, reported in DMSO39) and experimental pKa values (in ACN-H2O, see Supplementary Figs. 3-4) are listed if available.