ISOLATION AND STRUCTURE ELUCIDATION OF LOBOPHYTOSTEROL, DEPRESOSTEROL AND THREE OTHER CLOSELY RELATED STEROLS. FIVE NEW C28 POLYOXYGENATED STEROLS FROM THE RED SEA SOFT CORAL LOBOPHYTUM DEPRESSUM

Article abstract of DOI:10.1016/S0040-4020(01)88896-7

A series of polyoxygenated sterols were isolated from the soft coral Lobophytum depressum.The structure of five of these sterols was elucidated and determined to be; 5β,6β-epoxy-24ξ-methylcholestan-3β,22(R),25-triol (2a), 22(R),28-oxido-24ξ-methylcholest-5-en-3β,25,28-triol (1c, lobophytosterol), 24ξ-methyl-cholest-5-en-3β,22(R),25,28-tetraol (1b, depresosterol), and 5β,6β-epoxy derivatives of lobophytosterol and depresosterol, compounds 2c and 2b respectively.The structures were determined mainly on the basis of the fully interpreted 1H and 13C NMR spectra as well as the mass spectrum and several chemical transformations which resulted in unambiguous structures.All identified compounds belong to the C₂₈ category and are the first examples of marine sterols possessing the C₂₈-atom in various oxidative states.