Probing the bioactive constituents from chemotypes of the sponge Psammocinia aff. bulbosa

Since the report of (+)-psymberin (2) in 2004, many synthetic groups have pursued the synthesis of this compound, and our group has further collected Psammocinia aff. bulbosa to successfully isolate more 2. With more (+)-psymberin (2) in hand, additional clonogenic studies, a therapeutic efficacy assessment, and the hollow fiber assay have been completed. The inconsistent production of (+)-psymberin (2) and the classification of six Psammocinia species are further discussed herein. The most recent of these six collections resulted in the isolation of a new brominated cyclic peptide, (-)-psymbamide A (4), which is the first report of a Psammocinia-derived compound in this peptide class. The planar structure was solved via dereplication with Marinlit, HRESIMS, and 1D and 2D NMR techniques, and the absolute configuration determined using Marfey's method.