Marine natural products are small- to medium- molecular weight compounds produced by marine plants, invertebrates and microbes that have stimulated interdisciplinary studies by chemists and biologists. From marine toxins that impact public health concerns to the search for new drugs from the sea, the study of biologically active marine natural products has profoundly influenced the course of discovery in fields ranging from pharmacology to cancer medicine. The first GRC in Marine Natural Products was convened by Paul J. Scheuer and Yuzuru Shimizu in 1975 at Santa Barbara, California. In 2004, the fifteenth Conference in this series will continue a tradition of exciting discovery and exploration of new frontiers in marine natural products. Extraordinary chemical diversity is the hallmark of marine natural products structures. Marine natural products, such as the ion-channel modulators gamma-conotoxins, ciguatoxins and tetrodotoxin, have found extensive use in neurorpharmacology and their properties continue to be the subject of new discovery. Novel classes of marine alkaloids have been found to intervene in key receptors of cell-cycle, enzymes or other targets and lead to insights into new therapeutics. Investigational drugs such as bryostatin-1, from the common fouling bryozoan, Bugula neritina, and ET-743, obtained from Ecteinascidia turbinata- an inhabitant of Caribbean mangroves - have been developed both by the National Cancer Institute and private pharmaceutical companies through to late-phase human clinical trials as effective anti-cancer treatments. Investigations of other promising new compounds, such as the antitumor compound discodermolide, from a deep-water sponge, Discodermia sp., are attended by one of the great challenges for 'drugs from the sea' - supply. State-of-the-art studies in molecular genetics, enzymology and biochemistry address the issues of biosynthesis of marine natural products by identifying and sequencing the genes involved in transcription-translation and regulation of their cognate enzymes. The future promises heterologous expression of important marine natural products through manageable microbial fermentation. Various halogenases are responsible for the introduction of halogen into marine natural products. It appears the structure-functions of some of these enzymes are quite different from those of 'terrestrial' cytochrome-based haloperoxidases and non-heme iron halooxidases. The total synthesis of marine natural products aims for no less than total control of bond construction and stereochemistry of complex molecules from simple starting materials. New methods for building carbon-carbon bonds and management of heteroatom reactivity lie at the cutting edge of organic synthesis. Modern tour de force construction of complex molecules, such as tetrodotoxin and ciguatoxin CTX3, showcase the power of synthesis to bring scarce molecules and otherwise unobtainable analogs to the laboratory for biological studies. The extraordinary diversity of marine life and global occurrence of marine natural products reprises some fundamental questions - how are they distributed and what are their natural functions? How do marine natural products serve their hosts and influence the life histories of individual species and even large-scale marine community structures? Studies in biodiversity and chemical ecology reveal roles of natural products and organizing principles; not only at the species level, but also within the context of marine environmental dynamics that shape communities ranging from tropical reefs to the Antarctic benthos.

The science of natural products was founded by pioneering scientists in chemistry and biology. We are saddened to have lost two great scientists within one year- Paul J. Scheuer and D. John Faulkner. A special session will feature tributes to these two iconoclasts, who have inspired so many. In addition, new results that will be presented in dedication to John and Paul who helped build the foundations of this unique science.