*3.1. Analytics*

Analytical [radio]-RP-HPLC. Reversed-phase high-performance liquid chromatography analysis was performed with the following instrumentation: UltiMate 3000 RS UHPLC pump, UltiMate 3000 autosampler, Ultimate 3000 column compartment (25 ◦C oven temperature), UltiMate 3000 Variable Wavelength Detector (Dionex, Germering, Germany; UV detection at λ = 220 nm) a radio detector (GabiStar, Raytest; Straubenhardt, Germany), Jupiter 5 µm C<sup>18</sup> 300 Å 150 × 4.6 mm (Phenomenex Ltd., Aschaffenburg, Germany) column with acetonitrile (ACN)/H2O/0.1% trifluoroacetic acid (TFA) as mobile phase; flow rate of 1 mL/min; gradient: 0.0–1.0 min 10% ACN, 1.0–12.0 min 10–60% ACN, 13.0–15.0 min 60–80% ACN, 15.0–16.0 min 80–10% ACN, and 16.0–20.0 min 10% ACN.

Preparative RP-HPLC. Sample purification via RP-HPLC was carried out as follows: Gilson 322 Pump with a Gilson UV/VIS-155 detector (UV detection at λ = 220 nm) using a PrepFC™ automatic fraction collector (Gilson, Middleton, WI, USA), Eurosil Bioselect Vertex Plus 30 × 8mm 5 µm C18A 300 Å pre-column and Eurosil Bioselect Vertex Plus 300 × 8mm 5 µm C18A 300 Å column (Knauer, Berlin, Germany) and following ACN/H2O/0.1% TFA gradients with a flow rate of 2 mL/min: gradient A: 0.0–5.0min 0% ACN, 5.0–35 min 0–50% ACN, 35.0–38.0 min 50% ACN, 38.0–40.0 min 50%–0 ACN. gradient B: 0.0–5.0 min 10% ACN, 5.0–40.0 min 10–60% ACN, 41.0–45.0 min 60% ACN, 46.0–50.0 min 60–80% ACN, and 51.0–55.0 min 80–10% ACN.
