ORIGINAL ARTICLEA set of interesting sequoiatones stereoisomers from a wetland soil-derived fungus Talaromyces flavus

Four interesting sequoiatones stereoisomers (1-4) were isolated from a wetland soil-derived fungus Talaromyces flavus by chiral HPLC. On the basis of comprehensive NMR and mass analyses, their planar structures were elucidated as the same as that of sequoiatone B. Among them, 1 and 3 (or 2 and 4) were a pair of enantiomers, and 1 and 2 (or 3 and 4) were a pair of stereoisomers with epimerization at C-12, which indicated that sequoiatione-type metabolites exist as enantiomers rather than as optically pure compounds in some strains. With the quantum chemical ECD calculations, the absolute configurations of C-8 in 1-4 were determined, which is the first report to establish the absolute configuration of C-8 in sequoiatones. However, the absolute configurations of C-12 in sequoiatones are still unsolved.

In our investigation, four stereoisomers of sequoiationes were isolated by chiral HPLC, whose planar structures were the same as that of sequoiatione B. Among them, 1 and 3 (or 2 and 4) are a pair of enantiomers, and 1 and 2 (or 3 and 4) are a pair of stereoisomers with epimerization at C-12, which indicated that sequoiatione-type metabolites exist as enantiomers rather than as optically pure compounds in some strains. Based on the analyses of experimental and quantum chemical ECD, it was found that the absolute configuration of C-8 in sequoiationes can be determined by ECD, which is the first time to discuss the absolute configuration of C-8 in sequoiationes.103