Swainsonine absolute configuration

Swainsonine is a trihydroxylated bicyclic indolizidine alkaloid with four chiral centres, whose relative stereochemistry was determined by X-ray crystallographic analysis and the absolute configuration was deduced on the basis of biosynthetic and asymmetric induction studies, and then confirmed by an enantiospecific synthesis from D-mannose [2a]. 

The absolute configuration of (-)-swainsonine (1) was deduced on the basis of its biosynthesis and unambiguous nuclear magnetic resonance assignments.The relative stereochemistry of swainsonine was determined by X-ray crystallography. Noncarbohydrates have been used for the total synthesis of swainsonine and its isomers.The first total synthesis of 1 has established its absolute stereochemistry as (15, 2i ,8i ,8ai )-... 

Control of absolute configuration in the synthesis of (—)-swainsonine (378) by Chemla and his colleagues was due to the presence of the chiral suffinyhmine in the (J2s)-intermediate (—)-621, which was made in five steps from D-erythronolactone (620) (Scheme 84). Diastereoselective addition of the aUenylzinc reagent 622 (prepared in situ from alkyne 623)... 

---