Chemical Emulation of the Biosynthetic Route to Anthrasteroids: Synthesis of Asperfloketal A

The anthrasteroid rearrangement has been discussed for the formation of the eponymous substance class since its discovery. We here report its chemical emulation from a plausible biogenetic precursor and show how it accounts for the formation of asperfloketals A and B through a mechanistic bifurcation event. As a result, these natural products arise from double Wagner- Meerwein rearrangements and, thus, are 1(10-*5),1(5 -*6)-and 1(10-*5),4(5-*6)diabeo-14,15-secosteroids, respectively. To establish an efficient route to a bioinspired precursor, we devised a sequence of orchestrated oxidative activation and rearrangement from ergosterol.

Automated summary

This study discusses the formation mechanism of the anthrasteroid rearrangement and provides experimental evidence through chemical emulation from a plausible biogenetic precursor. The formation of asperfloketals A and B is shown to be achieved through double Wagner-Meerwein rearrangements, resulting in 1(10-*5),1(5 -*6)- and 1(10-*5),4(5-*6)diabeo-14,15- secosteroids, respectively. An efficient route to a bioinspired precursor is established by a sequence of orchestrated oxidative activation and rearrangement from ergosterol.