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