Epimeric Excolides from the Stems of <i>Excoecaria agallocha</i> and Structural Revision of Rhizophorin A

Abstract

Excolides A–B (<b>1</b>–<b>4</b>) represent the first examples of a new class of secolabdanoids with an unprecedented framework, which were isolated from the stems of <i>Excoecaria agallocha</i>. Their structures were determined by spectroscopic analysis, chemical modifications, CD, and single-crystal X-ray analysis (<b>1</b> and <b>4</b>) as excolide A (<b>1</b>), 11-<i>epi</i>-excolide A (<b>2</b>), 11,13-di-<i>epi</i>-excolide A (<b>3</b>), and excolide B (<b>4</b>). In addition, the structure of rhizophorin A (<b>7</b>), a novel bicyclic secolabdanoid, was revised as excolide A (<b>1</b>)