Arenaran sesquiterpenes from the nudibranch Chromodoris strigata and its dietary sponge Acanthodendrilla sp. 2510: spectroscopic and computational studies

Oxygenated sesquiterpenes were isolated from the sponge Acanthodendrilla sp. 2510 and identified as caparrapi oxide (1) and the bioactive oxocene sesquiterpene, arenaran A (2). An extract of the nudibranch Chromodoris strigata, found feeding on the sponge, also contained 2. Also characterized from the sponge extract were three compounds 3–5 derived from the oxocene skeleton of arenaran A that possessed hydroperoxy functionality. The structure and stereochemistry of each compound was identified using 1D and 2D NMR spectroscopic and mass spectrometry techniques, in combination with X-ray crystallography and molecular modelling/computational studies. Isolation of the hydroperoxy products provided insight into the reactivity of the oxocene skeleton

Catalyst-Controlled Stereoselective Synthesis Secures the Structure of the Antimalarial Isocyanoterpene Pustulosaisonitrile-1

Three new isocyanoditerpenes (5-7) have been characterized from Australian specimens of the nudibranch Phyllidiella pustulosa. The planar structure and (3R,6S,7R) absolute configuration of pustulosaisonitrile-1 were deduced by spectroscopic analyses at 900 MHz informed by molecular modeling, DFT calculations, and computational NMR chemical shift predictions and by comparison of experimental electronic circular dichroism (ECD) data with TDDFT-ECD calculations for the truncated model compound 8. A catalyst-controlled enantio- and diastereoselective total synthesis of the two most likely diastereomeric candidates for the structure of 5 solidified its (3R,6S,7R,10S,11R,14R) absolute configuration. Three individual enantioselective methods provided stereochemical control at key positions, permitting an unambiguous final structural assignment. Isocyanide 5 and synthetic diastereomers 5a and 5c showed activity against Plasmodium falciparum malaria parasites (IC ∼1 μM)