*3.5. Methylation of* **3**

Compound **3** (0.5 mg) was converted to methyl ester **3a** by treatment with an excess (1.5 mL) of a saturated solution of diazomethane in diethyl ether. The obtained derivative **3a** was analyzed using 2D-NMR and HRESIMS (Figure 2, substructure Va, Figure S23).
