For all new quinine-based QASs (4Br, 1Asp-4Asp, 1Ala-4Ala), spectral analysis was performed using FT-IR, 1 H NMR and 13 C NMR techniques. The results of the spectral characterization of the products are shown in Supplementary Data (Figs. A.1-A.27). In the 1 H NMR spectrum of 4Br, a triplet occurred at a chemical shift of 5.59 ppm, which was not visible in the spectra of 1-alkylquininium bromides (1Br-3Br). This signal was identified as originating from the hydroxyl group in the substituent in 4Br. Moreover, in the 13 It should be noted that methods for complete removal of dihydroquinine prior to derivatization of the alkaloid are known, although they require expensive and waste-generating preparative techniques (e.g., HPLC or UPLC with special stationary phases ). No significant signals from other organic impurities were observed in the NMR spectra. Nevertheless, it was noted that the introduction of proteinogenic amino acid anions notably alters the chemical shifts of hydrogen atoms in 1-alkylquininium or 1-(2-hydroxyethyl)quininium cations, particularly in the quinuclidine group, compared to the spectra of the corresponding bromides (Fig. ).