The unexpected isolation of CTP-431, a novel thiopyrone from the sponge Cacospongia mycoffijiensis

A reinvestigation of a Fijian collection of Cacospongia mycofijiensis has yielded the known mycothiazole and a novel heterocyclic, CTP-431 (1). Its structure including absolute configuration as 8R,9R,10S,13S was established using NMR data, calculated DFT (13)C chemical shifts and results from X-ray crystallography. It is possible that the tricyclic skeleton of CTP-43 1 (1) is biosynthetically related to the macrolide latrunculin A, however the thiopyrone moiety of 1 has no previous precedent in natural products chemistry.