RESUMEN
The total synthesis of the heptacyclic natural product isoquinocyclinone has been achieved. A Hauser annulation was used to assemble the anthraquinone core structure. The unique 2,4,5,6-tetrahydropyrrolo[2,3-b]pyrrole substructure was prepared by alkyne addition to a lactone intermediate and subsequent Ni(0) -mediated cyanide addition, the conversion of an O,O- into an N,O-acetal, and final intramolecular N-alkylation.
RESUMEN
A convergent and effective synthesis of the pyrrolopyrrole substructure (CDEFG) of the isoquinocyclines is reported. A key step is a tin-lithium exchange of an imidato-alkenyltin compound (a ring G equivalent) and the subsequent acylation with a lactone. The resulting acetal is used successfully for the ring F closure to the pyrrolopyrrole. The sole formation of the isoquinocycline N,O-acetal epimer is in accordance with the proposed mechanism for the isomerization of quinocyclines to isoquinocyclines.
