AbstractThe novel metabolite dendryphiellin A ( = (+)‐(1R,2S,8aR)‐ 1,2,6,7,8,8a‐hexahydro‐7‐hydroxy‐1,8a‐dimethyl‐6‐oxonaphthalen‐2‐yl (6R*, 2E,4E)‐8‐hydroxy‐6‐methylocta‐2,4‐dienoate; (+)‐1) is isolated from cultures of the marine deuteromyceteDendryphiella salina. There is no precedent in fungi for trinor‐eremophilanes or for branched C9carboxylic acids, the two classes of compounds constituting (+)‐1. The structure is secured by NMR spectroscopy and hydrolysis of (+)‐1 to give the side‐chain moiety ((6R*,2E,4E)‐8‐hydroxy‐6‐methylocta‐2,4‐dienoic acid (2)) intact, whilst the trinor‐ermophilane moiety is decomposed. The absolute configuration at the trinor‐eremophilane moiety is established from exciton