New cytotoxic salinosporamides from the marine actinomycete salinispora tropica

An extensive study of the secondary metabolites produced by the obligate marine actinomycete Salinispora tropica (strain CNB-392), the producing microbe of the potent proteasome inhibitor salinosporamide A, has led to the isolation of seven related gamma-lactams. New SAR data for all eight compounds indicate that the cholorethyl moiety plays a major role in the enhanced activity of salinosporamide A.