To a stirred solution of 5-((2,4,6-trimethoxystyrylsulfonyl)methyl)-2-methoxy-phenyl dibenzyl phosphate (4.36 g, 6.7 mmol) in anhydrous DCM (40 mL) under nitrogen at 0° C. was added bromotrimethylsilane (2.14 g, 2.1 eq). The resulting mixture was stirred for 45 minutes and monitored by TLC. sodium When the reaction was complete, aqueous sodium thiosulfate (1%, 50 mL) was added and the resulting mixture was stirred for an additional 5 minutes. The organic phase was separated and the aqueous phase was extracted with ethyl acetate (3×25 mL). The combined organic extract was concentrated in vacuo to afford the crude 5-((2,4,6-trimethoxystyrylsulfonyl)methyl)-2-methoxyphenyl dihydrogen phosphate. The product was purified column chromatography on silica eluted with a methanol/chloroform gradient to yield 1.4 g of the purified product having a melting point of 202-205° C.
