Two benzaldehyde derivatives and their artefacts from a gorgonian-derived Eurotium sp. fungus

Abstract

Two new benzaldehyde derivatives, named 3′-OH-tetrahydroauroglaucin (1) and(3′S*,4′R*)-6-(3′,5-epoxy-4′-hydroxy-1′-heptenyl)-2-hydroxy-3-(3′′-methyl-2′′-butenyl)benzaldehyde (2), were isolated from a gorgonian-derived Eurotium sp. fungus. Their structures were determined by extensive spectroscopic analysis including NMR and MS spectra. Dissolved 1 in CDCl₃ for several days could be detected its 2H-chromene skeleton derivatives (1a/1b), a pair of enantiomers with opposite configurations at C-3′. Compound 2 was also found to chemically convert to a pair of epimers non-enzymatically. The plausible mechanism to form the 2H-chromene artefacts with racemisation at C-3′ undergoing nucleophilic substitution (S_N1) was proposed.

Keywords:

• Gorgonian-derived fungus
• Eurotium sp
• benzaldehyde derivative
• 2H-chromene
• racemisation

Acknowledgments

We thank Dr. Chang-Lun Shao, School of Medicine and Pharmacy, Ocean University of China, for collection of the gorgonian samples and useful advice.