Isopalhinine A, a Unique Pentacyclic <i>Lycopodium</i> Alkaloid from <i>Palhinhaea cernua</i>

A new pentacyclic (5/6/6/6/7) <i>Lycopodium</i> alkaloid named isopalhinine A (<b>1</b>), which possesses a sterically congested architecture built with a tricyclo[4.3.1.0<sup>3,7</sup>]decane (isotwistane) moiety and a 1-azabicyclo[4.3.1]decane moiety, and palhinines B (<b>2</b>) and C (<b>3</b>) were isolated from <i>Palhinhaea cernua</i>. The structure and absolute configuration of <b>1</b> were elucidated by a combination of NMR spectra, optical rotation calculation, and X-ray diffraction experiment. A possible biogenetic pathway was also proposed.