Synthesis of Steroidal D-Ring-Fused Pyrrolidines of Dehydroepiandrosterone

The commercially available steroid dehydroepiandrosterone 3-acetate (DHEA) was converted into steroidal D-ring-fused pyrrolidines that combine two privileged structures: a steroid and a (2-arylethyl) amine. The three-step transformations proceeded through conversion of the C-17 ketone into an enol ether, followed by high-pressure-mediated cascade [4+2]/[3+2] cycloadditions with two nitroalkenes ([4+2]) and five dipolarophiles ([3+2]) to yield azonite intermediates. Finally, reduction of these azonites formed the new azasteroids, which are suitable for further derivatization.