Ochracenoids A and B, Guaiazulene-Based Analogues from Gorgonian Anthogorgia ochracea Collected from the South China Sea

Two new guaiazulene-based analogues, ochracenoids A (1) and B (2), along with four known analogues (3-6), were isolated from the gorgonian Anthogorgia ochracea collected from the South China Sea. The planar structures of the new compounds were elucidated by comprehensive spectroscopic data. The absolute configuration of 1 was determined as 3R by the comparison of TDDFT calculated electronic circular dichroism with its experimental spectrum. Compound 1 is a rare guaiazulene-based analogue possessing a unique C-16 skeleton. The possible generation process of 1 through an intermolecular one-carbon-transfer reaction was also discussed. Compound 2 was previously described as a presumed intermediate involved in the biogenesis of anthogorgienes A and I. Compound 3 exhibited antiproliferative effects on the embryo development of zebrafish Danio rerio.