In our search for biomedically important metabolites from Japanese marine invertebrates, the hydrophilic extract of the marine sponge Penares aff. incrustans strongly inhibited the binding of ^<125>I-labeled ω-conotoxin to rat brain synaptic plasma membranes. Bioassay-guided isolation afforded an inseparable mixture of closely-related diacylated unusual polyamines. The EtOH extract of the frozen sponge (1kg) was partitioned between H_2O and Et_2O, and the aqueous layer was further extracted with n-BuOH. The MeOH-soluble material of the n-BuOH fraction was subjected to various chromatographies to yield a mixture of penaresamides (1, 20.3mg, 2.0×10^<-3>% yield). The mixture of penaresamides was positive to both ninhydrin and Dragendorff reagents, suggesting their basic nature. Interpretation of the HOHAHA spectrum indicated that penaresamides were acylated polyamine. Penaresamides were hydrolyzed with 2N HCl at 110℃ followed by solvent partitioning to afford penaresamine (2) and a mixture of fatty acids. The structure of 2 was determined by spectral data. GC-MS analysis of the methylated fatty acid fraction disclosed the presence of five C_<11> fatty acids. Penaresamides exhibited a FABMS peak at m/z 773, corresponding to a molecular formula of C_<44>H_<94>^<35>Cl_2N_6O_2. Spectral data led to the structures of the bisamides of penaresamine (2) containing two C_<11>-fatty acids. Therefore, the structures of penaresamides (1) were elucidated to be diacylated polyamine. The proposed structures were confirmed by a total synthesis of panaresamide A, which posseses two unbranched acyl groups. The natural penaresamides (1) and the synthetic penaresamide A inhibited the binding of ^<125>I-ω-conotoxin to N-type Ca^<2+> channels with IC_<50> values of 1.3μM and 5.8μM, respectively.
