Fragment-Based Online OzESI-MS, NMR, and Computational DP4+/DFT Approaches to the Characterization of the Putative Biosynthetic Lipid Precursor of Atkamine from Latrunculia Alaskan Sponges

The extraction of Latrunculia sponges collected along the coast of the Aleutian Islands of Alaska yielded a lipid fraction, in which a natural long-chain monounsaturated aldehyde, (Z)-docos-15-enal (1), was isolated for the first time from this genus of sponge. Experimental, DP4+/DFT structure-probability calculations, and ab initio NMR chemical shift (CS) computational data comparing (Z)-docos-15-enal isolated from a natural sponge source with the previously reported synthetic material, confirmed the cis (Z) configuration of the double bond. Online ozonolysis LC-ESI-MS (OzESI) data validated the assignment of the C-15/C-16 olefin along the lipid chain. Aldehyde-based metabolites may serve as biosynthetic precursors for complex lipid alkaloids such as the atkamine pyrroloiminoquinone (PIQ).