Synthesis of a new allelopathic agent from the biotransformation of <i>ent</i>-15<i>α</i>-hydroxy-16-kauren-19-oic acid with <i>Fusarium proliferatum</i>

<p>The use of kaurane diterpenes as substrates in fungal biotransformation to achieve bioactive compounds has been widely reported. In this work, the natural product kaurenoic acid, a diterpene widely distributed in the plant Kingdom, was chemically converted into <i>ent</i>-15α-hydroxy-kaur-16-en-19-oic acid (<b>1</b>). Substrate <b>1</b> was subjected to biotransformation by the fungus <i>Fusarium proliferatum</i>, furnishing a new derivative, <i>ent</i>-2<i>α</i>,15α-dihydroxy-kaur-16-en-19-oic acid (<b>2</b>). The structure of metabolite <b>2</b> was deduced on the basis of spectroscopy and MS data. Derivative <b>2</b> showed allelopathic activity on germination and growth of root and stem of lettuce (<i>Lactuca sativa</i>), inhibiting 100% of germination and growth of roots and stem, at higher concentration assayed (10<sup>−4</sup> mol/L).</p>