| Abstract |
The ability of easily accessed 1,2-O-protected 5-azido-3-C-(ethoxycarbonyl)methylenefuranoses to serve as precursors for the generation of imino sugar derivatives containing an alpha,beta-unsaturated lactone or ketone functionality has been investigated. A key aspect was the propensity of the corresponding deprotected delta-amino alpha,beta-unsaturated esters to undergo 5-aminofuranose/iminopyranose isomerization. Acid hydrolysis of the d-amino (Z)-alpha,beta-unsaturated ester followed by treatment with base led to a butenolide-containing N-ethylformamide arising from a rearrangement of the imino-sugar-fused butenolide intermediate induced by the conjugated system. When carrying out the ring expansion step under neutral conditions, a 2-keto imino sugar was obtained that was readily converted into a 1,2-dihydropyridin-3-one by acetylation. Furthermore, reduction of the delta-azido (E)-alpha,beta unsaturated ester to the amine was followed by spontaneous intramolecular cyclization, providing the related furanose-fused unsaturated delta-lactam. |
