The absolute stereochemistry of saraines A-C (2–4), a class of unusual polycyclic alkaloids from the Mediterranean sponge Reniera sarai, has been elucidated by applying high field 1H-NMR to Mosher's method. The structures of saraine-B (3) and saraine-C (4), only partially clarified previously, now have been fully characterized by extensive analysis of their NMR spectra.

A new macrocyclic diamine alkaloid, named isosaraine-3 (9), has been isolated from the Mediterranean sponge Reniera sarai. The structures of both this new compound and saraine-3 (6), until now only partially clarified, have been completely elucidated by extensive spectroscopic studies. The absolute stereochemistry of the quinolizidone systems present in the co-occurring major alkaloids, saraine-1 (4) and saraine-2 (5), has been determined by applying advanced Mosher's method to the alcohol derivatives (10–13).

Eight new minor triterpenoids have been characterized from a lipid-soluble extract of Raspaciona aculeata. All are based on the same carbon skeleton as raspacionin [1]. The full assignment of all H-1- and C-13-nmr resonances has led to the rationalization of the effects of certain substituents on the chemical shifts of atoms in the perhydrobenzoxepine system.

A new triterpenoid, raspacionin B [4], has been isolated from the Mediterranean sponge Raspaciona aculeata. The structure and relative stereochemistry of 4 were elucidated by means of spectral methods, mainly ID and 2D nmr. The absolute stereochemistry was proposed by comparison of its cd curve with those of related compounds. The triterpenoid skeleton of raspacionin B, characterized by the presence of a cyclopropane ring, is related to those of terpenoids co-occurring in the same sponge.

1.1. The Mediterranean sponge Reniera sarai, Pulitzeri-Finali, 1969 (Demospongiae: Haploscleridae: Renieridae) posseses in large amounts a series of unprecedented polycyclic alkaloids, saraines 1–3 and saraines A–C.2.2. The structural peculiarities of saraines, their chemical-physical characteristics, along with their relevant abundance in the sponge, prompted a study aimed at investigating their biological properties.3.3. Saraines were assayed for their cytotoxic, antibacterial, insecticidal and potential antitumoral activities. These results, along with the growth inhibition of fertilized sea urchin eggs, are reported.

A new rearranged triterpenoid, raspacionin-A (3), has been isolated from the encrusting red sponge Raspaciona aculeata. The structure was unambiguously determined by X-ray diffraction studies on its deacetyl derivative (4), All 1H- and 13C-NMR resonances of 3 and 4 were assigned by an extensive use of 1D and 2D NMR techniques. The absolute stereochemistry was assigned by applying Mosher's method to 4.

An extensive application of two-dimensional proton-proton and proton-carbon shift correlated spectroscopy allowed the structural elucidation of isosaraiane-2, a minor component of an unique family of alkaloids from the sponge Reniera sarai.