Résumé : Three novel meroditerpenoids, strongylophorine‐1 (1), ‐2 (2) and ‐3 (3) have been isolated from the sponge Strongylophora durissima, Strongylophorine‐1 and ‐3 possess structure 1 and 3 respectively, as established by their spectral properties, hemisynthesis and chemical intercorrelation. The structure of strongylophorine‐2 has been shown to be 2 by X‐ray diffraction analysis on its monoacetylderivative (13). Copyright © 1978 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim