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Cytotoxic Diterpenoid Pseudodimers from the Korean Sponge Phorbas gukhulensis

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journal contribution
posted on 18.02.2016, 19:27 by Ju-eun Jeon, Lijuan Liao, Heegyu Kim, Chung J. Sim, Dong-Chan Oh, Ki-Bong Oh, Jongheon Shin
Four new cytotoxic diterpenoid pseudodimers (25), along with a previously reported one, gukulenin A (1), were isolated from the marine sponge Phorbas gukhulensis collected off the coast of Gagu-do, Korea. These novel compounds, designated gukulenins C–F (25), were determined by extensive spectroscopic analyses to be pseudodimers of the gagunins, like gukulenin A. The termini of the tropolone-containing side chains in gukulenins C–E (24) were found to have diverse modifications involving acetamides or taurine, whereas gukulenin F (5) was formed from 1 by the ring-opening of a cyclic hemiketal. The relative and absolute configurations were assigned by Murata’s and modified Snatzke’s methods using a HETLOC experiment and a CD measurement of a dimolybdenum complex, respectively. All of these compounds exhibited significant cytotoxicity against the K562 and A549 cell lines.