849767-21-1

Oxalyl chloride (5.71 g, 0.0450 mol) was dissolved in anhydrous dichloromethane (125 mL) and cooled to -78°C under nitrogen protection. Dimethyl sulfoxide (7.03 g, 6.4 mL, 0.0900 mol) dissolved in anhydrous dichloromethane (25 mL) was added slowly and dropwise through an addition funnel. The reaction mixture was stirred at -78 °C for 15 minutes before compound 16 (12.40 g, 0.0360 mol) dissolved in anhydrous dichloromethane (50 mL) was added dropwise through the addition funnel. Stirring was continued at -78 °C for 60 min, followed by the addition of triethylamine (10.92 g, 15.0 mL, 0.108 mol), and the reaction mixture was stirred at -78 °C for an additional 20 min, then warmed to 0 °C and stirred for 30 min. Upon completion of the reaction, the reaction was quenched by the addition of water (200 mL), the organic layer was separated and the aqueous layer was extracted with dichloromethane. The organic phases were combined, dried with anhydrous magnesium sulfate, filtered and concentrated. Purification by silica gel column chromatography (eluent: ethyl acetate/hexane, 1:4) afforded Product 17 (11.90 g, 0.0347 mol, 97% yield) as a light yellow oil. Mass spectrum (FAB-MS): m/e 344.

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