A new approach for the asymmetric syntheses of 2-epi-deoxoprosopinine and azasugar derivatives

A new approach to 2-epi-deoxoprosopinine , 1-deoxygulonojirimycin , and l-gulono-1,5-lactam was described. The C-2 hydroxymethyl group was introduced regioselectively using SmI2 mediated coupling of (S)-3-silyloxyglutarimide with either chloromethyl benzyl ether or the Beau–Skrydstrup reagent , followed by debenzylation and highly cis-diastereoselective reductive deoxygenation. Adoption of the Savoiʹs chemoselective ring-opening alkylation method allowed a highly diastereoselective introduction of the lipid side chain of 2-epi-deoxoprosopinine in a straightforward manner. Dehydration followed by highly trans-diastereoselective dihydroxylation led to polyoxygenated lactam derivative as a key intermediate for the syntheses of and .