3β-O-Glycosylated 16β-acetoxy-9β-H-lanosta-7,24-diene-3β,18,20β-triol, an intermediate metabolite from the sea cucumber Eupentacta fraudatrix and its biosynthetic significance

► New minor 4,4,14-trimethylsterol glycoside with unprecedented hydroxyl group at C-18 has been isolated from Eupentacta fraudatrix. ► Its structure allows to clarify some peculiarities of glycoside biosynthesis. ► Aglycone moiety biosynthesis does not precede glycosylation, but is concurrent. ► 9β-H configuration and type of unsaturation are formed in early biosynthetic stages.