Kabirimine, a New Cyclic Imine from an Okinawan Dinoflagellate

On our quest for new bioactive molecules from marine sources, two cyclic imines ( , ) were isolated from a dinoflagellate extract, inhibiting the growth of the respiratory syncytial virus (RSV). Compound was identified as a known molecule portimine, while was elucidated to be a new cyclic imine, named kabirimine. The absolute stereochemistry of was determined by crystallographic work and chiral derivatization, whereas the structure of was elucidated by means of spectroscopic analysis and computational study on all the possible isomers. Compound showed potent cytotoxicity (CC < 0.097 µM) against HEp2 cells, while exhibited moderate antiviral activity against RSV with IC = 4.20 µM (95% CI 3.31-5.33).