B-norsteroids from Hymenoscyphus pseudoalbidus.
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.
Department of Chemistry, Uppsala BioCenter, Swedish University of Agricultural Sciences, P.O. Box 7015, Uppsala SE-75007, Sweden.
Pierre F
PF
Andersson
Stina
S
Bengtsson
Jan
J
Stenlid
Anders
A
Broberg
D000734:Androstenediols / Q000737:chemistry; D001203:Ascomycota / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D009654:Norsteroids / Q000737:chemistry / Q000302:isolation & purification*; D013261:Sterols / Q000737:chemistry
D000734:Androstenediols; D009654:Norsteroids; D013261:Sterols; C555154:asterogynin A; C055608:viridiol