Survey of Chemical Syntheses of the Pyrrolizidine Alkaloids Turneforcidine and Platynecine

The necine bases turneforcidine and platynecine have inspired a great deal of synthetic effort.Key challenges include the construction of the bicyclic pyrrolizidine ring system and controlled introduction of three contiguous stereocenters.This review will survey the many diverse strategies by which these natural products have been synthesized.Pyrrolizidines 1 are a class of alkaloids found in various plant families (Figure 1). 2 A number of polyhydroxylated pyrrolizidines are potent inhibitors of glucosidase I 3 and also have been found in an