De-O-benzylation of sterically hindered benzyl ethers

Sterically hindered benzyl ethers that cannot be removed by hydrogenolysis with a variety of catalysts are removed readily by the reaction with N-brom osuccinimide and light in the presence of aqueous calcium carbonate, a reac tion developed by Binkley and Hehemann. It was found that these conditions are compatible with the presence of phthalimides and glycosyl sulfides and fluorides, in addition to the groups previously shown to be inert.