Novel polyhydroxylated cyclic nitrones and N-hydroxypyrrolidines through BCl3-mediated deprotection.

A general method to prepare a new class of carbohydrate-derived, enantiomerically pure polyhydroxypyrroline N-oxides from their alkoxy (protected) derivatives is presented. Boron trichloride is shown to cleave efficiently benzyl ethers and ketals without affecting the imine N-oxide functionality of nitrones. The same reagent (BCl3) also allowed the efficient synthesis of a polyhydroxylated N-hydroxypyrrolidine, giving access to a novel class of N-hydroxyiminosugars.