Symplocin A, a Linear
Peptide from the Bahamian Cyanobacterium <i>Symploca</i> sp. Configurational Analysis of <i>N</i>,<i>N</i>-Dimethylamino Acids by Chiral-Phase HPLC of Naphthacyl Esters
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Abstract
The absolute stereostructures of the components of symplocin
A (<b>3</b>), a new <i>N</i>,<i>N</i>-dimethyl-terminated
peptide from the Bahamian cyanobacterium <i>Symploca</i> sp., were assigned from spectroscopic analysis, including MS, 2D
NMR, and Marfey’s analysis. The complete absolute configuration
of symplocin A, including the unexpected d-configurations
of the terminal <i>N</i>,<i>N</i>-dimethylisoleucine
and valic acid residues, was assigned by chiral-phase HPLC of the
corresponding 2-naphthacyl esters, a highly sensitive, complementary
strategy for assignment of N-blocked peptide residues where Marfey’s
method is ineffectual or other methods fall short. Symplocin A exhibited
potent activity as an inhibitor of cathepsin E (IC<sub>50</sub> 300
pM)