Four indolizidine based alkaloids (IBAs) have been synthesized in a highly enantioselective, straightforward, and flexible manner. As a key step our previously developed Brønsted acid catalyzed vinylogous Mannich reaction was employed which easily afforded gram amounts of an optically pure central intermediate which can be converted into a wide range of diversely substituted IBAs.

A General Organocatalytic Approach Toward the Enantioselective Total Synthesis of Indolizidine Based Alkaloids. -Indolizidine based alkaloids (V), (XI) are synthesized in a highly enantioselective straightforward, and flexible manner. Key step is the vinylogous Mannich reaction of aldehyde (I), amine (III) and dienolates (II) and (VI) which gives the desired Mannich adducts even in gram amounts. Optically pure lactams (IV) and (VII) are readily converted into diversely substituted title compounds by known methods. -(ABELS, F.; LINDEMANN, C.; KOCH, E.; SCHNEIDER*, C.; Org. Lett. 14 (2012) 23, 5972-5975, http://dx.