The isolation and synthesis of polyandrocarpamines A and B. Two new 2-aminoimidazolone compounds from the Fijian ascidian, Polyandrocarpa sp

Chemical investigation of a Fijian ascidian, Polyandrocarpa sp., has resulted in the isolation of two new 2-aminoimidazolone-derived compounds, polyandrocarpamines A (1) and B (2). The structures of these unique metabolites were determined by the interpretation of spectroscopic data and confirmed by total synthesis. The stereospecific synthesis of 1 was accomplished using aldol condensation chemistry to generate an arylidene thiohydantoin that was subsequently transaminated to yield polyandrocarpamine A. Demethylation of synthetic 1 afforded polyandrocarpamine B. Both the natural product and synthetic polyandrocarpamines were assigned Z geometries about the exocyclic double bond (C-5/C-7) on the basis of C/H long-range coupling constants, which were measured using a gHSQMBC experiment.