I. Identification and structure elucidation of cytotoxic chamigrenes from the red alga Laurencia sp. II. Synthetic studies toward the sponge metabolite salicylihalamide A

Bioassay-guided fractionation of a cytotoxic extract from an undetermined species of red alga of the genus Laurencia afforded chamigrenes I-IV*. The structures were determined by spectral analysis. The structure of cartilagineol (I) was confirmed by crystallographic methods. The discovery of I lends credence to the theory of the existence of four different stereochemical lineages for polyhalogenated chamigrene sesquiterpenes from Laurencia. These compounds are moderately cytotoxic against some colon and prostate cancer cell lines in the National Cancer Institute's 60-cell human tumor assay. COMPARE analyses of I-IV were done with other chamigrenes to elucidate their structure-activity relationships.; Model studies toward the total synthesis of the marine natural product salicylihalamide A (V) were carried out. Salicylihalamide A (V), isolated from an Australian sponge of the genus Haliclona, displays a potent and unique differential cytotoxicity pattern in the NCI 60-cell assay. Three different routes toward the stereoselective synthesis of the allyl salicylate moiety of V were attempted.; *Please refer to dissertation for diagrams.