Guianolides A and B, New Carbon Skeletal Limonoids from the Seeds of <i>Carapa guianensis</i>

Two novel limonoids, named guianolides A (<b>1</b>) and B (<b>2</b>), were isolated from the seeds of <i>Carapa guianensis</i> AUBLET (Meliaceae). Their structures were established by spectroscopic analyses and X-ray crystallography. Guianolides A (<b>1</b>) and B (<b>2</b>) featured an unprecedented carbon skeleton via the formation of a C-11–C-21 bond