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Updated: Jul 15, 2026

A Direct, Early Stage Guanidinylation Protocol for the Synthesis of Complex Aminoguanidine-containing Natural Products
Published on: September 9, 2016
Enantioselective total synthesis of guanacastepene N using an uncommon 7-endo Heck cyclization as a pivotal step
Shin Iimura1, Larry E Overman, Ralph Paulini
1Department of Chemistry, 1102 Natural Sciences II, University of California, Irvine, 92697-2025, USA.
Abstract:
A convergent, enantioselective total synthesis of (+)-guanacastepene N was developed that features a 7-endo Heck cyclization as the key step. In the course of this synthesis, short syntheses of the enantiomerically pure cyclopentenone and cyclohexene building blocks 5 and 6, which constitute A and C ring fragments of guanacastepene N, were developed. These fragments were linked by a challenging conjugate addition reaction that also generated the C11 quaternary carbon stereocenter. Regioselective 7-endo Heck cyclization gave rise to a tricyclic intermediate, which was elaborated to complete the first total synthesis of guanacastepene N and the second enantioselective total synthesis of a guanacastepene natural product.
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