Minor and Trace Sterols in Marine Invertebrates. 26.¹ Isolation and Structure Elucidation of Nine New 5α,8α-Epidioxy Sterols from Four Marine Organisms

Sixteen 5α,8α-epidioxy ∆6 and ∆^6,9(11) sterols, of which nine are new, have been isolated from the marine organisms Ascidia nigra, Dendrogyra cylindrus, Thalysias juniperina, and Aplysia dactyLornela by reverse-phase highperformance liquid chromatography and characterized by high-resolution mass spectrometry and 360-MHz proton NMR spectroscopy. Attention is drawn to some unusual concentration-dependent NMR shifts of methyl signals. The probable biological significance of these epidioxy sterols is discussed with special reference to sterol biosynthesis.