Sinularamides A-G, Terpenoid-Derived Spermidine and Spermine Conjugates with Casitas B-Lineage Lymphoma Proto-Oncogene B (Cbl-b) Inhibitory Activities from a Sinularia sp. Soft Coral.

An extract of a Sinularia sp. soft coral showed inhibitory activity against the E3-ubiquitin ligase casitas B-lineage lymphoma proto-oncogene B (Cbl-b). Subsequent bioassay-guided separation of the extract provided a series of terpenoid-derived spermidine and spermine amides that were named sinularamides A-G (1-7). Compounds 1-7 represent new natural products; however, sinularamide A (1) was previously reported as a synthetic end product. The structures of sinularamides A-G (1-7) were elucidated by analysis of spectroscopic and spectrometric data from NMR, IR, and HRESIMS experiments and by comparison with literature data. All of the isolated compounds showed Cbl-b inhibitory activities with IC50 values that ranged from approximately 6.5 to 33 μM.