Enantioselective construction of a polyhydroxylated pyrrolidine skeleton from 3-vinylaziridine-2-carboxylates: synthesis of (+)-DMDP and a potential common intermediate for (+)-hyacinthacine A1 and (+)-1-epi-australine.

We report an enantioselective synthesis of the polyhydroxylated pyrrolidine alkaloid (+)-DMDP. The key steps in the synthesis were guanidinium ylide mediated asymmetric aziridination, stereospecific ring opening of trans-3-vinylaziridine-2-carboxylate with an oxygen nucleophile, iodine-mediated 5-endo-trig amino cyclization, and Prévost displacement. In addition, a potential common intermediate for the polyhydroxylated pyrrolizidine alkaloids (+)-hyacinthacine A(1) and (+)-1-epi-australine was synthesized from a diastereoisomeric cis-aziridine coformed in the asymmetric aziridination using the same strategy. A rationale for the diastereoselectivity observed for the iodine-mediated amino cyclization reactions is proposed on the basis of the heats of formation of the products.