Penicichrysol A: an unprecedented polyketide produced by <i>Penicillium chrysogenum</i>

Penicichrysol A (1), a highly oxygenated polyketide with an unprecedented skeleton, uniquely defined by multiple contiguous quaternary carbons, was isolated as a racemate from an endophytic fungus <i>Penicillium chrysogenum</i> that was sourced from the bulbs of the medicinal plant <i>Lycoris radiata</i>. Besides, three known biosynthetically related metabolites 2-4 were also obtained. The structure including the configuration of 1 was established <i>via</i> a combination of NMR spectroscopy and single-crystal X-ray diffraction analysis. A plausible biosynthetic pathway involving intriguing radical coupling and hemiketal reactions as key chemical transformations has been proposed.