Fig. 3: Chemoselectivity studies for N-alkylpyridinium reagents.

a Gibbs free energy profile for the addition reaction of methanethiolate anion to compound 1. b Gibbs free energy profile for the addition reaction of amines (MeNH2) to compound 1. c Model reactions of compound 1 with 7 and 8. d HPLC traces of model reaction between compound 1 and 7 (and 8) at 4 mM, phosphate buffer (PB) pH 7, after 4 h. e HPLC traces of the reactions between compound 1 and different nucleophilic amino acids (tyrosine, methionine, arginine, histidine, tryptophan, aspartic acid). f Evaluation of the conversions of reactions between compound 1 and 7 at different pH after 4 h. g Reaction profile of compound 1 and formation of compound 9 determined as percentage with reference to the internal standard (Fmoc-Phe-OH) by integration of the HPLC peak. Single HPLC injections were performed for semi-quantitative analysis. f-g Source data are provided as a Source Data file.