Structural characterization of hypoglycin B,a diastereomeric dipeptide from the ackee fruit (Blighia sapida Koenig) by NMR experiments

The dipeptide hypoglycin B, one of two toxins of the ackee fruit (Blighia sapida Koenig), was characterized for the first time by NMR spectral data, which led to the discovery that it exists naturally as a pair of diastereomers. No distinction was observed in the ¹H NMR signals of the diastereomers; however, complete and distinct ¹³C NMR assignments for the individual diastereomers were made. The ¹³C NMR spectrum of hypoglycin B compared very well with that of the corresponding signals in the spectrum for hypoglycin A, which is one of its constituent amino acids. The ¹H and ¹³C NMR assignments were further supported by DEPT, gCOSY, gHSQC and gHMBC experiments. Copyright © 2009 John Wiley & Sons, Ltd.