The crude solid was purified over silica gel chromatography (DCM/MeOH 0–25%) to obtain the desired product 1 (113 mg, 0.13 mmol,17%). Compound 1 was added to a solution of 2 (140 mg, 0.12 mmol, 1 ...

To a solution of 15 (100 mg, 302 μmol, 1 equiv) in THF (3 mL) and H 2 O (400 μL) was added p -toluenesulfonic acid (5 mg, 30 μmol, 0.1 equiv). The mixture was then stirred at room temperature until ...