Two new eicosanoids with a unique isovalerianic acid ester group at C-12, named dichotellates A (1) and B (2), were isolated from the gorgonian Dichotella gemmacea collected from the South China Sea using bioassay-guided fractionation. Their structures were established on the basis of extensive spectroscopic analysis including one-dimensional (1D) and two-dimensional (2D) NMR as well as high-resolution ESI-MS experiments. These two compounds were evaluated for their lethal activity toward brine shrimp Artemia salina and both showed weak activity.