Isolation of Montecristin, a Key Metabolite in Biogenesis of Acetogenins from Annona muricata and Its Structure Elucidation by Using Tandem Mass Spectrometry

During the course of our continuing search for acetogenins from Annonaceae, a new metabolite, montecristin, possibly involved in the biogenesis of acetogenins, was isolated from the roots of Annona muricata. Its structure was elucidated on the basis of UV, IR, (1)H and (13)C NMR, and mass spectrometry. The identification of the main stuctural features of montecristin (1) was obtained from the NMR spectra whereas their locations on the alkyl chain were evidenced by using mass spectrometry. The attribution of each carbon and location of substituents on the alkyl chain of this fatty acid gamma-lactone was evidenced by using tandem mass spectrometry (MS/MS) and high-energy collisional activation of [M + Li](+) lithium complexes. Finally, the structure determination of montecristin was strengthened by epoxidation and transformation leading to a known adjacent bis-tetrahydrofuran acetogenin.