The proposed project covers the total synthesis of two indolizidine (resp. quinolizidine) aLkaloids, allopumiliotoxin 323B' and homopumiliotoxin 321, of high pharmacological potential. A nitrone cycloaddition, which has already proven its synthetical usefulness, will be applied to construct the central indolizidine core. In a preliminary study, using a simpler test system, the factors governing the formation of the transition state of the central nitrone cycloaddition will be scrutinized. Special attention will be given to the role of allylic stereocontrol exerted by the substituents. Applying this knowledge to a fully functionalized nitrone, the total synthesis of allopumiliotoxin 323B' will be carried out. The proposed synthetic scheme is highly convergent since the indolizidine core and the side chain are constructed as separate entities which are coupled late during the synthesis. The fact that the overall synthesis uses non-chiral pool starting materials to produce a homochiral natural product, renders it highly versatile, and will enable the preparation of a range of other members of this family of alkaloids, e.g. the quinolizidine alkaloid homopumiliotoxin 321.