KOUMBALONE-A AND KOUMBALONE-B, NEW CASBANE DITERPENES FROM MAPROUNEA-AFRICANA

The organic extract of Mapronnea africana yielded koumbalones A [1] an d B [2], defined by spectral methods as new variations on the casbane ring system. The gross structures, relative configurations, and soluti on conformations were determined by a combination of spectral analyses and molecular modeling. Because koumbalone A spontaneously converts t o koumbalone B at room temperature, koumbalone B may be an artifact of isolation.