*3.6. Desulfation of* **3**

Compound **3** (<0.1 mg) was dissolved in 500 μL H2O and 16 μL of concentrated TFA was added and kept at 100 ◦C for 4 h. The reaction mixture was concentrated and purified by CC on YMC-GEL (1.5 × 2 cm) and eluted successively with H2O→EtOH. The subfraction eluted with EtOH was concentrated to give **11**. The obtained derivative was analyzed using HRESIMS (Figure 4, Figure S24).
