Sodium Thiosulfate → (3S,4S)-1-Benzyloxycarbonyl-3-(tert-butoxycarbonyl)amino-4-formylpyrrolidine

(3S,4S)-1-Benzyloxycarbonyl-3-(tert-butoxycarbonyl)amino-4-hydroxymethylpyrrolidine (1.00 g, 2.85 mmol) was dissolved in dichloromethane (40 mL). Under cooling with ice, Dess Martin reagent (1.42 g, 3.42 mmol) was added thereto, and the resultant mixture was stirred at room temperature for 2 hours under a nitrogen atmosphere. Under cooling, 5% aqueous sodium thiosulfate solution (50 mL) was added thereto, followed by stirring for 0.5 hours. The aqueous layer was extracted with dichloromethane (30 mL×1), and the organic layer was washed sequentially by a 0.05 mol/L aqueous sodium hydroxide solution (60 mL) and saturated brine (100 mL), and dried over anhydrous sodium sulfate. After filtration, the filtrate was concentrated under reduced pressure, to thereby yield the title compound as a colorless oily substance (0.90 g, 91%).