AULOSIRAZOLE, A NOVEL SOLID TUMOR SELECTIVE CYTOTOXIN FROM THE BLUE-GREEN-ALGA AULOSIRA-FERTILISSIMA

Aulosirazole, the major cytotoxin in the blue-green alga (cyanobacteri um) Aulosira fertilissima Ghose (UH strain DO-8-1), shows solid tumor selective activity in the Corbett assay. Its structure has been determ ined to be oxy-3-methoxynaphtho[2,3-d]-1,2-thiazole-4,9-dione by a com bination of spectroscopic, notably NMR, and X-ray crystallographic met hods. The carbon skeleton and the juglone nature of 1 was determined b y two-dimensional H-1-C-13 NMR correlation spectral analysis and one-d imensional C-13-C-13 decoupling experiments, the latter on the C-13-en riched cytotoxin. The presence of an isothiazole ring and the position of attachment for the juglone system was rigorously established by an X-ray crystallographic study.