A solution of tert-butyl[(2R)-1-{[tert-butyl(diphenyl)silyl]oxy}-3-oxopropan-2-yl]carbamate (3, 3.12 g, 7.3 mmol) in DME (30 ml) was treated with solid (2-nitrobenzyl)(triphenyl)phosphonium bromide(3.76 g, 7.86 mmol) (or any other suitable phosphonium salt), the mixture stirred at room temperature under N2 atmosphere for 30 min and then the reaction flask was charged with a solid mixture of potassium carbonate (1.78 g, 12.86 mmol) and 18-crown-6 (219 mg, 0.83 mmol). The purple mixture was further stirred at the same temperature for 14 h; diluted with DCM, washed with saturated NaHCO3, dried over MgSO4, filtered and concentrated Purified through a chromatographic cartridge of silicagel (50 g) eluted with 10% to 35% EtOAc in hexane to get 1.52 g (38% yield) of title compound as light yellow oil. MS: m/z=569.2 (MNa+).
