A Route to (2α,3β,4α)-(±)-2-(Hydroxymethyl)-3,4-pyrrolidinediol Based on the α-Silyloxyallylation of a Glycolaldehyde-Derived Nitrone

A protected form of title compound 6a, whose two enantiomers are known to be potent α-glycosidase inhibitors, was obtained through a five-step synthesis based on two thoroughly diastereo-controlled steps. An anti-selective α-silyloxyallylation of nitrone 9 afforded hydroxylamine 8a which, after O-silylation, was subjected to iodocyclisation to give 5-iodomethylisoxazolidine 7a as a single diastereoisomer. Displacement of iodide by mesylate and hydrogenolysis of mesylate 7b furnished 6b in 20 % overall yield starting from tert-butyldimethylsilyloxyacetaldehyde.