Precoated silica gel plate f254

All chemicals and solvents were purchased with the highest degree of purity (Sigma-Aldrich, Darmstadt, Germany; Alfa Aesar, Karlsruhe, Germany; VWR, Milan, Italy) and used without further purification. The reactions were monitored by TLC (precoated silica gel plate F254, Merck, Darmstadt, Germany) and the products were detected by exposure to ultraviolet radiation, iodine vapor, and chromic mixture. Column chromatography: Merck Kieselgel 60 (70–230 mesh). The purity of compounds was determined by CHNS analysis and was ≥ 95% in all cases. NMR spectra were acquired on NMR spectrometers operating at 200 MHz (Varian, Palo Alto, California), 400 MHz (Bruker AVANCE, Billerica, Massachusetts, US) or 500 MHz (Varian Inova, Palo Alto, California, US), using CDCl₃ solutions unless otherwise specified. Coupling constant values (J) were reported in Hz, details in Supplementary Materials.

Silibinin 1 was purchased from Sigma-Aldrich (Milano, Italy). HPLC-grade ACN and CH₃OH were purchased from Carlo Erba Reagents and Sigma-Aldrich. Unless otherwise indicated, other chemicals were obtained from Sigma Aldrich. For the experimental synthesis procedures of tyrosol-based building blocks 6–8, see Romanucci et al. 2021 [37 (link)]. It must be noted that the experimental procedures for the synthesis of compounds 10–12 and 13–15 were described in detail only for the stereoisomer of silybin A (SilA, 1a): the same reaction conditions (temperature, stoichiometric ratios, and time of reaction) were used for silybin B (SilB, 1b) and silibinin (Sil, 1ab) as a natural mixture. Reactions were monitored by TLC (precoated silica gel plate F254, Merck, Upper Gwynedd, PA, USA) and column chromatography: Merck Kieselgel 60 (70–230 mesh). The analysis was performed with a Shimadzu (Tokyo, Japan) LC-8A HPLC system equipped with a Shimadzu SCL-10A VP System control and Shimadzu SPD-10A VP UV-VIS Detector. HPLC purifications were carried out on a Phenomenex Gemini RP18 column (10 μm particle size, 21.20 mm × 250 mm i.d.) using a linear gradient of ACN in 0.1 M NH₄Ac in H₂O, pH 7.0, from 20% to 100% over 30 min at a flow rate of 8 mL/min, with detection at 288 and 260 nm. MALDI spectral data were acquired on a MALDI TOFTOF AB Sciex 5800 mass spectrometer.