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

摘要

A new approach to 2-epi-deoxoprosopinine 11, 1-deoxygulonojirimycin 7, and l-gulono-1,5-lactam 9 was described. The C-2 hydroxymethyl group was introduced regioselectively using SmI2 mediated coupling of (S)-3-silyloxyglutarimide 13b with either chloromethyl benzyl ether 16a or the Beau–Skrydstrup reagent 16b, followed by debenzylation and highly cis-diastereoselective reductive deoxygenation. Adoption of the Savoi's chemoselective ring-opening alkylation method allowed a highly diastereoselective introduction of the lipid side chain of 2-epi-deoxoprosopinine 11 in a straightforward manner. Dehydration followed by highly trans-diastereoselective dihydroxylation led to polyoxygenated lactam derivative 27 as a key intermediate for the syntheses of 7 and 9.