General Procedure B: Freshly distilled Et3N (0.28 mL, 2.0 mmol, 2.0 equiv) and pivaloyl chloride (0.17 mL, 1.4 mmol, 1.4 equiv) were added sequentially to a pre-cooled (-78 ℃), stirred solution of the corresponding acrylic acid in THF (10.0 mL) under argon. The resulted mixture was stirred for 5 mins at -78 ℃, 40 mins at room temperature, and then cooled again to -78 ℃. To another flask containing N-PMP-tertbutansulfinamide (1.0 mmol, 1.0 equiv) in 5.0 mL of THF at -78 ℃ was added n BuLi , and the mixture was stirred for 30 min at -78 ℃ under argon. The latter solution was then transferred to the mixed anhydrides solution via cannula, and the resulting mixture was stirred for 2.5 h at -78 ℃ under argon. Then solution was quenched with saturated aqueous ammonium chloride. The reaction mixture was extracted with ethyl acetate. The combined organic layers were washed with 1 M NaOH (3 × 15 mL) and brine (3 × 15 mL), dried over anhydrous MgSO4, filtered, and concentrated under vacuum. The residue was purified by flash column chromatography on silica gel (3:1 to 1:1 pentane/ethyl acetate) to yield the desired product.