Arenosclerins A−C and Haliclonacyclamine E, New Tetracyclic Alkaloids from a Brazilian Endemic Haplosclerid SpongeArenosclerabrasiliensis

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Abstract
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 brasiliensis, a species endemic to the southeastern Brazilian coast. The alkaloids were isolated as their hydrochloride salts and identified by analysis of spectroscopic data. Data obtained from 1H− 1H COSY, HMBC, and HSQC−TOCSY NMR experiments allowed complete assignment of the 1H and 13C resonances, and analysis of the NOESY and ROESY spectra showed that the only differences between 2, 3, and 4 were the relative stereochemistries of the bispiperidine ring system. Arenosclerins A−C are the first haliclonacyclamine/halicyclamine-related alkaloids with a hydroxy group in the bridging alkyl chain.