Prenylated Benzophenones from <i>Triadenum japonicum</i>

Six new prenylated benzophenones, (−)-nemorosonol (<b>1</b>) and trijapins A–E (<b>2</b>–<b>6</b>), were isolated from the aerial parts of <i>Triadenum japonicum</i>. (−)-Nemorosonol (<b>1</b>) and trijapins A–C (<b>2</b>–<b>4</b>) have a common tricyclo­[4.3.1.0^3,7]­decane skeleton, while <b>1</b> is an enantiomer of (+)-nemorosonol previously isolated from <i>Clusia nemorosa</i>. The absolute configuration of (−)-nemorosonol (<b>1</b>) was assigned by ECD spectroscopy. Trijapins A–C (<b>2</b>–<b>4</b>) are analogues of <b>1</b> possessing an additional tetrahydrofuran ring. Trijapins D (<b>5</b>) and E (<b>6</b>) are prenylated benzophenones with a 1,2-dioxane moiety and a hydroperoxy group, respectively. (−)-Nemorosonol (<b>1</b>) exhibited antimicrobial activity against <i>Escherichia coli</i> (MIC, 8 μg/mL), <i>Staphylococcus aureus</i> (MIC, 16 μg/mL), <i>Bacillus subtilis</i> (MIC, 16 μg/mL), <i>Micrococcus luteus</i> (MIC, 32 μg/mL), <i>Aspergillus niger</i> (IC₅₀, 16 μg/mL), <i>Trichophyton mentagrophytes</i> (IC₅₀, 8 μg/mL), and <i>Candida albicans</i> (IC₅₀, 32 μg/mL), while trijapin D (<b>5</b>) showed antimicrobial activity against <i>C. albicans</i> (IC₅₀, 8 μg/mL)