| Abstract
| - An effective one-pot synthesis of polyhydroxylated quinolizidines from 1-C-(2‘-oxo-4‘-pentenyl)-5-azido-C-glycofuranosides was developed. Reduction of the 5-azido group using triphenylphosphine followedby base treatment produced quinolizidines in good yield. The base-mediated ring-opening β-eliminationproduced an acyclic α,β-conjugated ketone as a Michael acceptor, which was followed by an intramolecularnitrogen conjugate addition to form an aza-C-glycopyranoside intermediate. Meanwhile, the β,γ-doublebond of the aglycon migrated under the basic conditions to form another α,β-conjugated ketone. Thesubsequent intramolecular conjugate addition by the azasugar nitrogen led to the formation of thequinolizidines in a highly stereoselective manner. The stereoselectivity of the first conjugate additiongiving azasugar is affected by the stereochemistry of the monosaccharide substrate, whereas thestereoselectivity in the second conjugate addition was likely directed entirely by steric repulsion fromthe azasugar.
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