title: The marine sponge Agelas citrina as a source of the new pyrrole-imidazole alkaloids citrinamines A-D and N-methylagelongine.
abstract: 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.
authors.affiliation: Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung, Am Handelshafen 12, 27570 Bremerhaven, Germany.
authors.forename: Christine
authors.initials: C
authors.lastname: Cychon
authors.affiliation: Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung, Am Handelshafen 12, 27570 Bremerhaven, Germany.
authors.forename: Ellen
authors.initials: E
authors.lastname: Lichte
authors.affiliation: Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung, Am Handelshafen 12, 27570 Bremerhaven, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Köck
keywords: Agelas citrina; NMR; marine sponges; mauritiamine; pyrrole–imidazole alkaloids