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Molecules 2012, 17(7), 7769-7781; doi:10.3390/molecules17077769

B-norsteroids from Hymenoscyphus pseudoalbidus

1, 2, 2 and 1,*
Received: 5 June 2012 / Revised: 13 June 2012 / Accepted: 15 June 2012 / Published: 25 June 2012
(This article belongs to the Section Metabolites)
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Two viridin-related B-norsteroids, B-norviridiol lactone (1) and B-norviridin enol (2), both possessing distinct unprecedented carbon skeletons, were isolated from a liquid culture of the ash dieback-causing fungus Hymenoscyphus pseudoalbidus. Compound 2 was found to degrade to a third B-norsteroidal compound, 1β-hydroxy-2α-hydro-asterogynin A (3), which was later detected in the original culture. The proposed structure of 1 is, regarding connectivity, identical to the original erroneous structure for TAEMC161, which was later reassigned as viridiol. Compound 2 showed an unprecedented 1H-13C HMBC correlation through an intramolecular hydrogen bond. The five-membered B-ring of compounds 1–3 was proposed to be formed by a benzilic acid rearrangement. The known compound asterogynin A was found to be formed from 3 by a β-elimination of water. All compounds were characterized by NMR spectroscopy, LC-HRMS and polarimetry.
Keywords: Hymenoscyphus pseudoalbidus; Chalara fraxinea; B-norsteroids; secondary metabolites; structure elucidation Hymenoscyphus pseudoalbidus; Chalara fraxinea; B-norsteroids; secondary metabolites; structure elucidation
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Andersson, P.F.; Bengtsson, S.; Stenlid, J.; Broberg, A. B-norsteroids from Hymenoscyphus pseudoalbidus. Molecules 2012, 17, 7769-7781.

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