Synthesis of pentahydroxylated pyrrolizidines and indolizidines.

1,3-Dipolar cycloaddition reaction of nitrone 7 and chemo-enzymatically obtained alkenediols 12 and 13 has been used in the synthesis of pentahydroxylated pyrrolizidines (8 and 10) and indolizidines (9 and 11). The pyrrolizidinic and indolizidinic skeletons were built after internal n-alkylation of the suitably functionalized pyrroloisoxazolidine intermediates obtained by the necessary protecting group manipulations. This method expands the scope of cycloaddition reactions in the synthesis of new and highly polyhydroxylated sugar-like alkaloids.