RCC was determined based on radio-TLC (EtOAc/Hex 5:5). The crude reaction mixture was diluted with HEPES buffer (8 mL, 1.5 M, pH = 5.7) and loaded on a C8 plus cartridge. After flushing with water (5 mL) and elution with EtOH (0.8 mL) the crude product was purification by semi-preparative HPLC (Luna® 5 µm PFP(2) 100 Å, LC Column 250 x 10 mm). The product fraction (5 mL) was collected, diluted with water (20 mL) and trapped on a C18 cartridge. The cartridge was flushed again with water (5 mL) and the product was eluted with EtOH (0.