Saeki, B.M., Granato, A.C., Berlinck, R.G.S., Magalhães, A., Schefer, A.B., Ferreira, A.G., Pinheiro, U.G. and Hajdu, E., “Two Unprecedented Dibromotyrosine-Derived Alkaloids from the Brazilian Endemic Marine Sponge Aplysina caissara”, Journal of Natural Products, 65, 796-799 (2002). Errata: Journal of Natural Products, 2003, 66 (7): 1039-1039.

Abstract: Two new bromotyrosine-derived alkaloids, caissarine A (1) and caissarine B (2), along with three known biogenetically related alkaloids, aeroplysinin-1, fistularin-3 and the artifact of isolation 2-(3,5-dibromo-4-dimethoxy-1-hydroxy-2,5-cyclohexadien-1-yl)ethanamide, have been isolated from Aplysina caissara, an endemic species of marine sponge from the Southeastern Brazilian coast. The alkaloids have been identified by analysis of spectroscopic data. While caissarine A has a 2-hydroxyagmatine moiety in its structure, caissarin B is the first naturally-occurring compound encompassing the unprecedented 1,7-diamino-3-hydroxyheptane moiety.

Lira, T.O..; Nascimento, G. F. F..; Hajdu, E.; Berlinck, R. G. S..; Further Dibromotyrosine-Derived Metabolites from the Marine Sponge Aplysina caissara, Journal of the Brazilian Chemical Society, 2006, 17, 1233-1240.

Abstract: The re-investigation of the crude extract obtained from the sponge Aplysina caissara led to the isolation of five new dibromotyrosine derivatives, named agelocaissarines A1, A2, B1, B2 and caissarine C, along with the already known fistularin-3 and 11-hydroxyaerothionin. All compounds were identified by analysis of mono- and bidimensional NMR spectra, high resolution mass spectra, infrared and ultraviolet spectra. The relative stereochemistry of agelocaissarines could be established by analysis of 1H NMR spectra and molecular modeling, while the absolute configuration of the spiroxazolidine moieties of fistularin-3, caissarine C and 11-hydroxyaerothionin was established by analysis of 1H NMR and circular dichroism spectra. Fistularin-3 and 11-hydroxyaerothionin displayed moderate antibiotic activity against several pathogenic bacteria.