and water (30 mL). Then, it was treated with TCEP hydrochloride while stirring under an argon atmosphere for 20 hours. The mixture was extracted with water (300 mL) and ethyl acetate (3 × 250 mL). The organic layer was washed with brine (150 mL) and concentrated under reduced pressure. The residue was purified by silica gel column chromatography (hexane/EA 9:1) to obtain the pure thiol 2 as a desired product (27.3 g, 45%).