New piperidine alkaloids from two ladybird beetles of the genus Calvia (Coccinellidae)

The alkaloids of two coccinellid beetles, Calvia 14-gullata and C. 10-gutta ta have been studied. The major alkaloid of these two species is the new pi peridinic cis-lactone 1a, for which the name calvine has been coined. The c orresponding trans-lactone 1b (2-epicalvine) is also present as a minor con stituent (+/-10%) in both species. We report here the structure determinati on and the total synthesis of these compounds. Kept in methanolic solution, these lactones undergo epimerisation as well as opening of the lactone rin g leading to a complex mixture of nine main components.