| A study of biologically active extracts of several Pacific Ocean marine sponges has led to the isolation of eight new and nine previously known natural products. The structures of the compounds were determined by a combination of spectroscopic data analysis and chemical interconversions. In addition, the partial synthesis of imbricatine (3*), a cytotoxic metabolite of the starfish Dermasterias imbricata, was accomplished.;The sponge Acanthella sp. yielded ten sesquiterpenes, four of which were new. Compounds 80-87, 89 and 90 contained isonitrile, isothiocyanate, formamide, carbamate and chloride functional groups. In addition, violacene (88), a halogenated monoterpene previously isolated from the red algae Plocamium violaceum, was isolated from the sponge extracts.;The Northeastern Pacific sponge Neoesperiopsis digitata yielded neoesperlactone (96), an eighteen carbon fatty acid derived ;The study of the Papua New Guinea sponge Pseudoxinella massa led to the identification of a novel cyclic heptapeptide pseudaxinellin (103) which contained standard protein amino acid residues with the L configuration. The study of two species of marine sponges, Ptilocaulis trachys and Amphimedon sp., collected at Enewetak lagoon, led to the isolation and identification of the depsipeptide majusculamide C (104) which had previously been found in the blue green alga Lyngbya majuscula collected at Enewetak.;Crude extracts from the sponge Petrosia contignata collected in Papua New Guinea showed potent cytotoxicity against the murine leukemia L1210 cell line. These extracts yielded contignasterol (24), a new highly oxygenated steroid that inhibited histamine release from rat peritoneal mast cells with an IC;The synthetic confirmation of the tetrahydroisoquinoline substructure of the starfish metabolite imbricatine (3) was accomplished using a Pictet-Spengler reaction to couple the starting materials 3-(3,5-dihydroxyphenyl) alanine methyl ester (143) and sodium 3-(4-benzyloxyphenyl) glycidate (141). A series of deprotections and protections on the resulting racemic benzyltetrahydroisoquinoline led to a product 140 that was identical by... |
