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The Revised Structure of the Cyclic Octapeptide Surugamide A
Kenichi Matsuda1, Takefumi Kuranaga1, Ayae Sano1
1Faculty of Pharmaceutical Sciences, Hokkaido University.
Chemical & Pharmaceutical Bulletin
|May 8, 2019
Summary
Marine-derived surugamides are cyclic octapeptides with cathepsin B inhibitory activity. Chemical synthesis revealed that surugamide A contains D-allo-isoleucine, not D-isoleucine, challenging its natural biosynthesis.
Area of Science:
- Marine natural products chemistry
- Peptide synthesis
- Biochemistry
Background:
- Surugamides are non-ribosomal peptides from marine Streptomyces.
- Surugamide A and derivatives are cyclic octapeptides with cathepsin B inhibitory activity.
- The presence of D-isoleucine in natural peptides is rare due to complex biosynthesis.
Purpose of the Study:
- To synthesize surugamide A (1) containing D-isoleucine.
- To investigate the stereochemistry of the non-proteinogenic amino acid residue in surugamide A.
- To elucidate the biosynthetic implications of the identified amino acid residue.
Main Methods:
- Solid-phase peptide synthesis.
- Chemical synthesis of cyclic octapeptides.
- Chromatographic comparison and structural analysis.
Main Results:
- Solid-phase peptide synthesis successfully produced cyclic octapeptide 1.
- The synthesized structure of surugamide A (1) contained D-allo-isoleucine, not D-isoleucine.
- Chemical syntheses and chromatographic comparisons confirmed the presence of D-allo-isoleucine.
Conclusions:
- The biosynthesis of surugamide A likely involves a Cβ-epimerization pathway leading to D-allo-isoleucine.
- The synthetic route provides a method for producing surugamide analogs.
- The findings challenge previous assumptions about the stereochemistry of D-amino acids in natural peptides.
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