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Two Novel Hexadepsipeptides with Several Modified Amino Acid Residues Isolated from the Fungus

Ravindra, Gudihal and Ranganayaki, Rappal S and Raghothama, Srinivasa and Srinivasan, Mandayam C and Gilardi, Richard D and Karle, Isabella L and Balaram, Padmanabhan (2004) Two Novel Hexadepsipeptides with Several Modified Amino Acid Residues Isolated from the Fungus. In: Chemistry & Biodiversity, 1 (3). pp. 489-504.

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Two new cyclohexadepsipeptides have been isolated from the fungus Isaria. Fungal growth in solid media yielded hyphal strands from which peptide fractions were readily isolable by organic-solvent extraction. Two novel cyclodepsipeptides, isaridin A and isaridin B, have been isolated by reverse-phase HPLC, and characterized by ESI-MS and 1H-NMR. Single crystals of both peptides have been obtained, and their 3D structures were elucidated by X-ray diffraction. The isaridins contain several unusual amino acid residues. The sequences are cyclo(β-Gly-HyLeu-Pro-Phe-NMeVal-NMePhe) and cyclo(β-Gly-HyLeu-β-MePro-Phe-NMeVal-NMePhe), where NMeVal is N-methylvaline, NMePhe N-methylphenylalanine, and HyLeu hydroxyleucine (=2-hydroxy-4-methylpentanoic acid). The two peptides differ from one another at residue 3, isaridin A having an (S)-proline at this position, while β-methyl-(S)-proline (=(2S,3S)-2,3,4,5-tetrahydro-3-methyl-1H-pyrrole-2-carboxylic acid) is found in isaridin B. The solid-state conformations of both cyclic depsipeptides are characterized by the presence of two cis peptide bonds at HyLeu(2)-Pro(3)/HyLeu(2)-β-MePro(3) and NMeVal(5)-NMePhe(6), respectively. In isaridin A, a strong intramolecular H-bond is observed between Phe(4)CO⋅⋅⋅HNβ-Gly(1), and a similar, but weaker, interaction is observed between β-Gly(1)CO⋅⋅⋅HNPhe(4). In contrast, in isaridin B, only a single intramolecular H-bond is observed between β-Gly(1)CO⋅⋅⋅HNPhe(4

Item Type: Journal Article
Publication: Chemistry & Biodiversity
Publisher: John Wiley and Sons
Additional Information: Copyright of this article belongs to John Wiley and Sons.
Department/Centre: Division of Biological Sciences > Molecular Biophysics Unit
Division of Physical & Mathematical Sciences > Instrumentation Appiled Physics
Date Deposited: 24 Nov 2010 08:21
Last Modified: 30 Jan 2014 12:29
URI: http://eprints.iisc.ac.in/id/eprint/33891

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