The marine sponge Agelas citrina as a source of the new pyrrole–imidazole alkaloids citrinamines A–D and N-methylagelongine

The chemical investigation of the Caribbean sponge Agelas citrina revealed four new pyrrole–imidazole alkaloids (PIAs), the citrinamines A–D (1–4) and the bromopyrrole alkaloid N-methylagelongine (5). All citrinamines are dimers of hymenidin (6) which was also isolated from this sponge as the major metabolite. Citrinamines A (1) and B (2) are derivatives of the PIA dimer mauritiamine (7), whereas citrinamine C (3) is derived from the PIA dimer nagelamide B (8). Citrinamine D (4) shows an uncommon linkage between the imidazole rings of both monomeric units as it is only observed in the benzocyclobutane ring moiety of benzosceptrins A–C (9–11). Compound 5 is the N-methyl derivative of agelongine (12) which consist of a pyridinium ring and an ester linkage instead of the aminoimidazole moiety and the common amide bond in PIAs

Structure Elucidation of Submilligram Quantities of Natural Products – Application to Haliclamines G and H from the Arctic Marine Sponge Haliclona viscosa

Two new haliclamines were identified directly from the crude extract of the Arctic sponge Haliclona viscosa using improved chromatographic conditions and a detailed knowledge about the fragmentation pattern of haliclamines. These are haliclamine G (1) with two alkyl chains of equal length (10 methylene groups) and haliclamine H (2) with alkyl chains of 10 and 12 methylene groups. Due to the limited amount of sponge material available, the haliclamines were not isolated, and the structure elucidation relied on the chromatographic and mass spectrometric comparison with synthetic compounds</jats:p