Termination of the Chirality Confusion of Peribysins

Abstract Peribysins belong to a family of eremophilanes isolated from marine Periconia byssoides OUPS-N133 and terrestrial P. macrospinosa KT3863. Their absolute configurations were determined to be the (4S)-enantiomers based on the modified Mosher’s method, chemical derivatizations, density functional theory (DFT)-based electronic circular dichroism (ECD) spectral analysis, and DFT-based [α]D calculations. Danishefsky’s and Reddy’s total syntheses assigned the (4R)-forms for the marine peribysins despite agreeing with the (4S)-configuration for the terrestrial peribysin Q (5). This paper reports the successful solution of this chirality confusion of peribysins by reproducing the ECD spectrum of peribysin G bis(p-bromobenzoate) prepared from peribysin A (1) isolated from terrestrial P. byssoides TS60. 2β-Hydroxyperibysin A (6), which was isolated by changing the culture conditions of the above fungus, was converted to (4S)-peribysin E MTPA esters. These compounds showed identical 1H NMR spectral properties to those reported in the isolation paper.