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. 2025 Feb 7;147(7):5679–5692. doi: 10.1021/jacs.4c12928

Figure 2.

Figure 2

Development of one-pot multistep reaction with unsaturated aldehydes. (a) Reaction of lysine-containing peptide AcGKFV (1a) and free N-termini peptide GKFV (1b) with acrolein to generate heterocyclic FDP product on lysine (2a) and N-termini (2b). (b) Reagentless conversion of FDP-heterocycle to MP-heterocycle using FDP-containing peptides (2a, 2b) at 60 °C for 6 h (entry 2) or 80 °C for 3 h (entry 3). Interestingly, MP formation was not observed for N-terminal FDP. (c) Previous mechanism proposed in literature for formation of MP directly from lysine. In this mechanism, two molecules of acrolein add to lysine, first through Schiff base formation and then Michael addition. Morita–Bayllis–Hillman (MBH) reaction then results in cyclization and formation of the MP product. (d) New proposed mechanism for the formation of MP-lysine from FDP-lysine. Enol formation is followed by rearrangement, deoxygenation, and aromatization to furnish MP-lysine. Figure 2, created with BioRender.com, released under a Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International license (Agreement number: PB272TFJXT).