Chemical investigations of Indo-Pacific sponges: New structures and bioactivities

The contents of this dissertation describe the chemical investigations of three different marine sponges from the Indo-Pacific region with the hope of finding novel structures and probing for interesting biological activities. Three sponges (Leucetta sp., Leucosolenia sp. and Plakortis quasiamphiaster) were chosen for this work resulting in the isolation and characterization of three new compounds: (-)-spiroleucettadine, leucosolenamines A and B and plakinidine E.; The first chapter begins with an introduction to marine natural products chemistry, its inception, followed by its current status. This chapter ends with concluding remarks on the future of marine natural products chemistry. The chapters following the introductory chapter describe the research carried out in this dissertation. The contents of chapter two explore a new structural theme in 2-aminoimidazole alkaloids in Calcareous sponges. A Fijian collection of Leucetta species was fractionated resulting in the isolation of (-)-spiroleucettadine. The structural characterization and bioactivity testing of (-)-spiroleucettadine are reported in this chapter.; The third chapter includes the first chemical investigation into the Calcareous sponge Leucosolenia sp. that was collected in the Milne Bay region of Papua New Guinea. Two new imidazole alkaloids, leucosolenamines A and B, were isolated and characterized. In addition, the bioactivity of leucosolenamine A is reported. The fourth chapter stipulates the recollection and reinvestigation of a Vanuatu specimen of Plakortis quasiamphiaster . This project began with the aim of adding new structures to the pyrroloacridine class of compounds and to further explore their cytotoxicities. Fractionation of this sponge resulted in the isolation and characterization of a new plakinidine analogue, plakinidine E. Also explored in this chapter, are the selective bioactivities of plakinidines A and E.*; *Please refer to dissertation for diagrams.