Chemical investigation of extracts from the Irish deep-sea soft coral Anthothela grandiflora revealed cadinene-like sesquiterpenes, anthoteibinenes A-E, bearing unusual dimethylamine substitution. Structure elucidation was accomplished using 1D/2D NMR spectroscopy and high-resolution mass spectrometry, while NOESY NMR experiments, gauge invariant atomic orbital (GIAO) NMR calculations coupled with DP4+ probabilities measures, and ECD comparisons were incorporated to propose their relative and absolute configurations. Anthoteibinene B (2) exhibited 49% inhibition of respiratory syncytial virus (RSV) at 3.1 μM with no cytotoxicity.