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

Abstract

<jats:title>Abstract</jats:title><jats:p>The dipeptide hypoglycin B, one of two toxins of the ackee fruit (<jats:italic>Blighia sapida</jats:italic> 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 <jats:sup>1</jats:sup>H NMR signals of the diastereomers; however, complete and distinct <jats:sup>13</jats:sup>C NMR assignments for the individual diastereomers were made. The <jats:sup>13</jats:sup>C 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 <jats:sup>1</jats:sup>H and <jats:sup>13</jats:sup>C NMR assignments were further supported by DEPT, gCOSY, gHSQC and gHMBC experiments. Copyright © 2009 John Wiley &amp; Sons, Ltd.