Bioassay-Directed Isolation of Antibacterial Metabolites from an Arthropod-Derived .

Bioassay-directed isolation of secondary metabolites from an extract of TJ403-CA4 isolated from the medicinally valuable arthropod afforded five new and 10 known compounds (-). All the compounds (except ) belong to a minor class of highly rigid 6-5-5-5-fused tetracyclic cyclopiane-type diterpenes known to be exclusively produced by members of the genus. The structures and absolute configurations of the new compounds (-) were elucidated by extensive spectroscopic analyses, including HRESIMS and 1D and 2D NMR, single-crystal X-ray diffraction, and comparison of the experimental electronic circular dichroism data. Compounds and represent the first examples of cyclopianes bearing a C-20 carboxyl group; compound represents the first example of a cyclopiane with a -hydroxymethyl group; compound represents the second example of a cyclopiane bearing a hydroxy group at C-7; compound represents the first example of a cyclopiane bearing a hydroxy group at C-8. Compounds and exhibited activity against MRSA, with MIC values of 4.0 and 2.0 μg/mL, respectively. In addition, the structure-antibacterial activity relationship (SAR) of compounds - is discussed.