Abstract

Two new cyclopentapeptides, xylapeptide A (1) with an uncommon L-pipecolinic acid moiety, and xylapeptide B (2) having a common L-proline residue were identified from an associated fungus Xylaria sp. isolated from the Chinese medicinal plant Sophora tonkinensis. Their planar structures were elucidated by a comprehensive analysis of NMR and MS spectroscopic spectra. The absolute configurations were determined by Marfey’s method and single-crystal X-ray diffraction (Cu Kα) analysis. Xylapeptide A (1) is the first example of cyclopentapeptide with L-Pip of terrestrial origin and showed strong antibacterial activity against Bacillus subtilis and B. cereus with MIC value of 12.5 μg/mL.

Highlights

  • S. aureus, Shigella castellani, as well as strong antifungal activity against C. albicans

  • The absolute configuration of 1 was confirmed unambiguously by single-crystal X-ray analysis which indicated an L-configuration of pipecolinic acid (Pip) (Fig. 3)

  • Examination of the 2D NMR spectra revealed that 2 shared the same N-Me-Phe, Val, Ala, and Leu units with 1, the only difference is that the Pip in 1 was replaced by a proline (Pro) subunit in 2

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Summary

Introduction

S. aureus, Shigella castellani, as well as strong antifungal activity against C. albicans. Further analysis of 2D NMR spectrum allowed five subunits to be established, an N-Me-phenylalanine (N-Me-Phe), a valine (Val), an alanine (Ala), a leucine (Leu), and a pipecolinic acid (Pip) (Fig. 2). The configurations of the amino acid residues of 1 was determined by acid hydrolysis, derivatization with Nα-(2,4-dinitro-5-fluorophenyl)-L-alalinamide (L-FDAA, the advanced Marfey’s method12), and UPLC-MS analysis of the derivatives with comparison to the standards (Figure S17).

Results
Conclusion
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