Enantiospecific Total Synthesis of (−)‐Hyacinthacine A1 and (+)‐Hyacinthacine A1 and Their Homologues Using Nitrogen Substituted Donor–Acceptor Cyclopropane.

A concise and efficient enantiospecific total synthesis of (−)‐hyacinthacine A1 and (+)‐hyacinthacine A1 was achieved from commercially available starting material L‐pyroglutamic acid and D‐glutamic acid, respectively. For the synthesis of this trihydroxylated pyrrolizidine ring, we employed the nitrogen‐substituted donor‐acceptor cyclopropane as a key intermediate. The synthetic approach relies on two crucial steps, highly stereo‐ and regioselective intramolecular cyclopropanation with Rh2(OAc)4 and regioselective ring opening of a nitrogen‐substituted donor‐acceptor cyclopropane. [ABSTRACT FROM AUTHOR]