The total synthesis of (−)-spiroaspertrione A : A divinylcyclopropane rearrangement approach

Abstract

The rise of multidrug-resistant pathogens poses a major threat to global health, with methicillin-resistant Staphylococcus aureus (MRSA) among the most challenging. One promising approach to overcoming resistance is using small molecules that resensitize MRSA to existing drugs. Here, we report the enantioselective total synthesis of one such promising candidate, (−)-spiroaspertrione A, a complex meroterpenoid of the andiconin family. This natural product has long eluded synthesis because of its densely functionalized polycyclic backbone. Our route features a stereoselective Diels-Alder cycloaddition, followed by a key divinylcyclopropane rearrangement forming the spirobicyclo[3.2.2]nonane core, which proved to be reversible and was further investigated by density functional theory calculations. Strategic late-stage functionalization of the compact cage architecture enabled access to the natural product and provided evidence for a plausible biosynthetic relationship with (−)-aspermerodione.