Preface Marine natural products have attracted the attention of biologists and che nists the world over for the ast five decades.To date approximately600maintura products have been isolated from marine organ 6.800publications.In addition tothesepublicationsthere areapproximately another 9.000 publications which cover syntheses.reviews.biological activity studies ecological studies etc.on the subject of marine natural products.Several of the cdeofviy e o ceutically useful o npounds bu tificatio b of sea poradic and produc dictable h use toxic fish o toxins are produced by microorganisms such as dinoflagellates or marine bacteria and may pass through several levels ofthe food chain.The identification of marine oxins has been one of the most challenging areas of marine natural products hemistry. decde major occupation of marine naural products chemists for the past two nthe search f or potential pharmaceutical difficult to single that is c fin a place in medicine hown promise ns produce som for drug develo y toprovide ent studie Marine environment provides different biosynthetic conditions to organisms tha live in it marine organisms generally live in symbiotic association.the pathway of transfer of nutrients between symbiotic partners is of much importance and raises questions about the real origin of metabolites produced by association A recent trend in marine natural products chemistry is the study of symbiosis. oof bioacuve marne natural products provides many chalng Preface Marine natural products have attracted the attention of biologists and chemists the world over for the last five decades. To date approximately 16,000 marine natural products have been isolated from marine organisms and reported in approximately 6,800 publications. In addition to these publications there are approximately another 9,000 publications which cover syntheses, reviews, biological activity studies, ecological studies etc. on the subject of marine natural products. Several of the compounds isolated from marine source exhibit biological activity. The ocean is considered to be a source of potential drugs. Marine organisms not only elaborate pharmaceutically useful compounds but also produce toxic substances. One of the most important societal contribution of marine natural products chemists has been the isolation and identification of toxins responsible for seafood poisoning. Outbreaks of seafood poisoning are usually sporadic and unpredictable because toxic fish or shellfish do not produce the toxins themselves, but concentrate them from organisms that they eat. Most marine toxins are produced by microorganisms such as dinoflagellates or marine bacteria and may pass through several levels of the food chain. The identification of marine toxins has been one of the most challenging areas of marine natural products chemistry. The major occupation of marine natural products chemists for the past two decades has been the search for potential pharmaceuticals. It is difficult to single out a particular bioactive molecule that is destined to find a place in medicine. However, many compounds have shown promise. Marine organisms produce some of the most cytotoxic compounds ever discovered, but the yields of these compounds are invariably so small that natural sources are unlikely to provide enough material for drug development studies. The art by which marine organisms elaborate bioactive molecules is fascinating. Marine environment provides different biosynthetic conditions to organisms that live in it. Marine organisms generally live in symbiotic association. The pathway of transfer of nutrients between symbiotic partners is of much importance and raises questions about the real origin of metabolites produced by association. A recent trend in marine natural products chemistry is the study of symbiosis. Biosynthesis of bioactive marine natural products provides many challenging problems