Synthesis of fully substituted polyhydroxylated pyrrolizidines via Cope-House cyclization.

Total synthesis of the proposed structure of (−)-hyacinthacine C5 and its epimers at C6 and C7 is described. A key step of the synthesis was the construction of the bicyclic pyrrolizidine system by means of a nucleophilic addition of a dithiane to a cyclic nitrone followed by a Cope–House cyclization.