Structure revision and NMR data characterization of natural 3β,11-dihydroxy-9,11-secosteroids bearing a 5,6-epoxy group based on a single-crystal X-ray diffraction analysis

A comprehensive structural analysis was conducted on a natural product previously identified as 3β,11-dihydroxy-5β,6β-epoxy-24-methylene-9,11-secocholestan-9-one ( 1 ) [ 1 ], which was reisolated from the Taiwanese octocoral Sinularia lochmodes . Comparative analysis of 1D and 2D NMR data, supported by X-ray crystallography, led to the revision of this compound’s structure from 1 to its stereoisomer, 3β,11-dihydroxy-5α,6α-epoxy-24-methylene-9,11-secocholestan-9-one ( 2 ) ([ Fig. 1 ]). Based on these findings, the structures of several previously reported 3β,11-dihydroxy-9-oxo-9,11-secosteroids containing a 5,6-epoxy group should be re-evaluated by comparison with the NMR data of 2 [[ 2 ] [ 3 ] [ 4 ]. Furthermore, this study establishes a correlation between the 1 H/ 13 C NMR spectroscopic data and the absolute configurations of 9,11-secosteroids bearing either a 5α,6α- or 5β,6β-epoxy group. The corrected molecular structure 2 , along with structurally related compounds and accurately determined 1 H and 13 C NMR spectroscopic data confirmed in this study, could facilitate precise chemical structure assignments, enhance bioactivity predictions via molecular docking, and support reliable structure-activity relationship (SAR) analyses for future pharmaceutical research. Fig. 1 Reported structure, 3β,11-dihydroxy-5β,6β-epoxy-24-methylene-9,11-secocholestan-9-one ( 1 ) and revised structure 2 (3β,11-dihydroxy-5α,6α-epoxy-24-methylene-9,11-secocholestan-9-one) and a computer-generated ORTEP plot revealing the absolute structure of 3β,11-dihydroxy-5α,6α-epoxy-24-methylene-9,11-secocholestan-9-one ( 2 ). Publication History Article published online: 05 March 2026 © 2026. Thieme. All rights reserved. Georg Thieme Verlag KG Oswald-Hesse-Straße 50, 70469 Stuttgart, Germany