Salinosporamide A (Marizomib) is a potent proteasome inhibitor being studied as a potential anticancer agent.  It entered phase I human clinical trials for the treatment of multiple myeloma, only three years after its discovery in 2003. This marine natural product is produced by the obligate marine bacteria Salinispora tropica and Salinispora arenicola, which are found in ocean sediment. Salinosporamide A belongs to a family of compounds, known collectively as salinosporamides, which possess a densely functionalized γ-lactam-β-lactone bicyclic core.