Natural Occurrence, Synthesis and Biological Applications of Spermidine Alkaloids

Spermidine alkaloids are polyaminated macrocycles containing a lactam ring, which are biosynthetically derived from L-Orn or L-Arg via putrescine intermediates. The presence of these polyamines in nature is very limited, occurring in only a few plant families, and therefore the isolation of spermidine alkaloids serves chemotaxonomic purposes. The interest in the isolation and synthesis of these alkaloids also results from the structural complexity and broad range of bioactivity attributed to these macrocyclic structures. In recent years, several research groups have been dedicated to these triaminated compounds and previously unknown natural products, or already described structures in new plant species, with potential biological applications have been reported. Novel synthetic strategies and the application of more recent synthetic methodologies have allowed new perspectives for the development of new bioactive molecules. The latest progress on the isolation, identification, biological activity, and chemical synthesis of spermidine alkaloids is summarized in this review.