Five new biscembranoids, bistrochelides
A–E (3–7), were isolated together
with glaucumolides
A (1) and B (2) from the soft coral Sarcophyton trocheliophorum. Their structures and absolute
configurations were determined by spectroscopic methods, X-ray crystal
diffraction, and DFT/NMR (density functional theory/nuclear magnetic
resonance) and TDDFT/ECD (time-dependent density functional theory/electronic
circular dichroism) calculations. A new approach is introduced to
determine the relative configuration of a stereocenter through the
dynamic evaluation of the mean absolute errors (MAEs) between the
investigated diastereoisomers, moving from an “extended”
to a more diagnostic “restricted” set of atoms. This
research leads to the structure revision of glaucumolides A and B.
In in vitro immunomodulatory screening, compounds 1 and 4 significantly induced the proliferation of CD3+ T cells, while compounds 1 and 5 significantly
increased the CD4+/CD8+ ratio at 3 μM.