Conithiaquinones A and B, Tetracyclic Cytotoxic Meroterpenes from the Mediterranean Ascidian Aplidium conicum

Chemical investigation of the Mediterranean ascidian A. conicum resulted in the isolation of two new meroterpenes, the conithiaquinones A ( 1 ) and B ( 2 ), in addition to two previously reported chromenols ( 3 and 4 ) and conicaquinones ( 5 and 6 ). The structures of conithiaquinones A and B were determined by interpretation of spectroscopic data, and regiochemical and stereochemical assignments were achieved with the aid of computational methods, including the recently developed DP4 NMR spectral prediction method. Both conithiaquinones A and B showed significant effects on the growth and viability of cells, with 1 showing interesting cytotoxicity against human breast cancer cells.