Talaroclauxins A and B: Duclauxin-ergosterol and duclauxin-polyketide hybrid metabolites with complicated skeletons from Talaromyces stipitatus

Abstract

Talaroclauxins A and B (1 and 2), two novel duclauxin hybrids, were obtained from Talaromyces stipitatus, along with three new (3−5) and one known analogue (6). Their structures were determined by NMR spectroscopy, HRESIMS, single-crystal X-ray diffraction, and quantum chemical calculations. Compound 1 is the first example of duclauxin-ergosterol hybrid featuring an unprecedented dodecacyclic ring system formed via a [4 + 2] cycloaddition, while compound 2, bearing an unusual 6/6/6/5/6/6/6/6 ring system, is a new member of the rare duclauxin-polyketide hybrid class of natural products. Plausible biosynthetic pathways for 1−6 are proposed. Compound 5 displayed moderate neuroprotective effects in glutamate sodium-induced SH-SY5Y cells.