Flexible synthesis of poison-frog alkaloids of the 5,8-disubstituted indolizidine-class. II: Synthesis of (-)-<b>209B</b>, (-)-<b>231C</b>, (-)-<b>233D</b>, (-)-<b>235B"</b>, (-)-<b>221I</b>, and an epimer of <b>193E</b> and pharmacological effects at neuronal nicotinic acetylcholine receptors
Beilstein journal of organic chemistry