Isolation and structure determination of aplidinones A-C from the Mediterranean ascidian Aplidium conicum:: A successful regiochemistry assignment by quantum mechanical 13C NMR chemical shift calculations

A chemical investigation of a Mediterranean ascidian, Aplidium conicum, has resulted in the isolation of the new metabolites aplidinone A (1), B (2), and C (3). The structures of aplidinones A-C were determined by interpretation of spectroscopic data, whereas the regiochemistry was determined by the comparison of experimental C-13 NMR chemical shifts with those predicted by GIAO shielding calculations. (c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005.