Neogenkwanine I from the flower buds of <i>Daphne genkwa</i> with its stereostructure confirmation using quantum calculation profiles and antitumor evaluation

<p>Neogenkwanine I (<b>1</b>), a new daphnane-type diterpene with 4,7-ether group, along with four known ones (<b>2</b>–<b>5</b>), were isolated from <i>Daphne genkwa</i>. The structure including absolute configurations of <b>1</b> was established on the basis of NMR, <sup>13</sup>C-NMR and ECD calculations and CD exciton chirality analysis. <sup>13</sup>C-NMR and ECD calculations of daphnane-type diterpenes were reported here for the first time. All of the diterpenes were screened for their cytotoxic activities against MCF-7 and Hep3B cell lines. The cytotoxicity structure- activity relationship of compounds was illustrated with the absence of ortho-ester group of daphnane-type diterpenes.</p> <p></p>