Lanesoic Acid: A Cytotoxic Zwitterion from Theonella sp.

Lanesoic acid (1) was isolated and characterized from Theonella sp. during PharmaMar's ongoing program to study cytotoxic substances from marine sources. Its planar structure, elucidated by spectral analysis (NMR, IR, UV, and MS), possesses an unusual skeleton containing a tetrahydropyrimidine cation that is stabilized as a zwitterion by an internal carboxylate counterion. The stereostructure of 1 was deduced from ROESY-NOESY, J-based configurational analysis (JBCA), and density functional theory (DFT) computational calculations fitted using the recently published DP4+ parameter. Compound 1 was moderately active and selective against pancreas PSN1 cells (IC50 = 8.9 μg/mL) and inactive against colon HT-29, breast MD-MB-23, and NSCLC lung tumor cells.