Wiktionary
indolizidine
n. (context organic compound English) A bicyclic heterocycle containing a six-membered ring fused to a five-membered ring, one of the bridging atoms being nitrogen; any derivative of this compound, especially several alkaloids
Wikipedia
Indolizidine
Indolizidine is a heterocyclic chemical compound that forms the central core of the indolizidine alkaloids such as swainsonine.