Relative Configurational Assignment of 4-Hydroxyprorocentrolide and Prorocentrolide C Isolated from a Benthic Dinoflagellate ( Prorocentrum lima).

Herein, we clarify the structure and relative configurations of two prorocentrolide analogues (1 and 2) isolated from the benthic marine dinoflagellate Prorocentrum lima. The results of NMR spectroscopy show that 1 is prorocentrolide substituted by a hydroxy group at C-4, while the newly isolated compound 2 can be thought of as 1 lacking one ether ring and having one extra double bond. The relative configurations of all stereogenic centers and the configurations of the double bonds in 1 and 2 were determined utilizing ROESY correlations and J-based configuration analysis. Furthermore, 2 was shown to exhibit cytotoxicity against HCT-116 and Neuro-2a cells (IC50 2.2 and 5.2 μM, respectively.