Assignment of the CD Cotton Effect to the Chiral Center in Pseurotins, and the Stereochemical Revision of Pseurotin A₂.

Pseurotins A₁ (1) and A₂ (2) were isolated from a culture broth of the fungal strain Aspergillus fumigatus WFZ-25 as stereoisomers of pseurotin A (3) in 2011. We also isolated 1 and 2 together with 3 from A. fumigatus OUPS-T106B-5 separated from the marine fish Mugil cephalus. In this study, we re-examined the stereochemistry of 1 and 2 using chemical transformation and the CD spectra, and found the relationship between the CD Cotton effect and the absolute configurations of 1 and 2, which led us to revise the stereostructure of pseurotin A₂.