Arenosclerins A-C and haliclonacyclamine E, new tetracyclic alkaloids froma Brazilian endemic haplosclerid sponge Arenosclera brasiliensis

Arenosclerins A (2), B (3), and C (4), as well as haliclonacyclamine E (1), are new tetracyclic alkylpiperidine alkaloids isolated from a new species of marine sponge belonging to the order Haplosclerida, Arenosclera brasilie nsis, a species endemic to the southeastern Brazilian coast. The alkaloids were isolated as their hydrochloride salts and identified by analysis of sp ectroscopic data. Data obtained from H-1-H-1 COSY, HMBC, and HSQC-TOCSY NMR experiments allowed complete assignment of the H-1 and C-13 resonances, an d analysis of the NOESY and ROESY spectra showed that the only differences between 2, 3, and 4 were the relative stereochemistries of the bispiperidin e ring system. Arenosclerins A-C are the first haliclonacyclamine/halicycla mine-related alkaloids with a hydroxy group in the bridging alkyl chain.