The presence of sterically rigid contiguous quaternary stereocenters in natural products imposes conformational constraints with significant effects on their biological activities. However, achieving the direct synthesis of multiple contiguous quaternary stereocenters in a single step remains a formidable challenge. Here, we present the totalsynthesis of the antibacterial metabolite lugdunomycin (1) inthirteenstepsvia a sequence of photochemical transformations. A photoenolization, keto-enol tautomerization, and spiroketalization sequence was developed to generate the spiroketal 4from actinaph...
