Structurally Diverse Duclauxins from a Coral-Derived <i>Talaromyces</i> sp. and Insight into Determining the Configuration\nat C‑1 of Heptacyclic Duclauxins by <sup>1</sup>H NMR

A chemical\ninvestigation of the coral-derived fungus <i>Talaromyces</i> sp. TJ403-AL05 led to the isolation of 18 duclauxin analogues (<b>1</b>–<b>18</b>), 14 of which, taladuxins A–N\n(<b>1</b>–<b>14</b>), are new and consist of the\nfirst example of duclauxin fused with one 1,6-dioxaspiro[4.5]decan-2-one\nmoiety (<b>1</b>), as well as its biosynthetic product (<b>2</b>), and 12 6/6/6/5/6/6/6 heptacyclic derivatives (<b>3</b>–<b>14</b>). Comprehensive spectroscopic analyses, electronic\ncircular dichroism (ECD) calculations, DP4+ probability analyses,\nsingle-crystal X-ray diffraction, and vibrational circular dichroism\n(VCD) calculations were employed to characterize their structures\nand revise the published structure of verruculosin B. An efficient <sup>1</sup>H NMR method was established to discriminate 1<i>R</i> and 1<i>S</i> configurations at C-1 of 6/6/6/5/6/6/6 heptacyclic\nduclauxins according to chemical shift differences of diastereotopic\nmethylene H<sub>2</sub>-11 or H<sub>2</sub>-12 (Δδ<sub>H‑11</sub> or Δδ<sub>H‑12</sub>). Compounds <b>4</b>, <b>7</b>–<b>8</b>, <b>13</b>–<b>15</b>, and <b>18</b> exhibited moderate inhibition of <i>Arabidopsis thaliana</i> 4-hydroxyphenylpyruvate dioxygenase\n(<i>At</i>HPPD), with IC<sub>50</sub> values ranging from\n17.1 to 71.3 μM.