A. Goti et al., A straightforward route to enantiopure pyrrolizidines and indolizidines bycycloaddition to pyrroline N-oxides derived from the chiral pool, MOLECULES, 4(1), 1999, pp. 1-12
Enantiomerically pure, five membered cyclic nitrones, easily obtained in la
rge amounts from protected hydroxyacids and aminoacids such as D- and L-tar
taric, L-malic, and L-aspartic acids, give cycloaddition reactions with a g
ood diastereocontrol. The adducts of L-malic and L-aspartic acids derived f
rom addition of nitrones to dimethyl maleate and gamma-crotonolactone were
easily converted into enantiopure pyrrolizidinones, which can be transforme
d into polyhydroxypyrrolidines or polyhydroxypyrrolizidines, both interesti
ng compounds as potential glycosidase inhibitors. The method is suitable fo
r natural products synthesis as exemplified by a straightforward and conven
ient access to the pyrrolizidine alkaloid necine base (-)-hastanecine, as w
ell as to indolizidine alkaloids, i.e. (+)-lentiginosine.