**1. Introduction**

Octocorals of the genus *Briareum* (family Briareidae) [1–4] are proven to be the most important source to produce briarane-type diterpenoids [5]. The compounds of this type are only found in marine invertebrates, particularly in octocorals and demonstrated a wide spectrum of bioactivities, such as anti-inflammatory activity [6] and cytotoxicity [7]. In our continuing research into the chemical constituents of an octocoral *B. excavatum* (Nutting 1911), which was distributed extensively in the coral reefs of Taiwan, have resulted in isolation of three previously unreported 8,17-epoxybriaranes–briarenols I–K (**1**–**3**) along with two known analogues, briaexcavatolide P (**4**) [8] and briaexcavatin P (**5**) [9], (Figure 1). In the current study, the comprehensive workflow of isolation, structure determination, and anti-inflammatory activity evaluation, was implemented on briaranes **1**–**5**.

**Figure 1.** Structures of briarenols I–K (**1**–**3**), briaexcavatolide P (**4**), briaexcavatin P (**5**), excavatolide B (**6**), and briareolide B (**7**).
