Ileabethoxazole (1), a new perhydroacenaphthene-type diterpene alkaloid containing the uncommon benzoxazole moiety, was isolated from the Caribbean sea whip Pseudopterogorgia elisabethae. The structure of 1 was elucidated by extensive spectroscopic data interpretation. Ileabethoxazole showed 92% inhibition of Mycobacterium tuberculosis (H37Rv) at the concentration range of 128-64 μg/mL. © 2006 Elsevier Ltd. All rights reserved.