Starfish saponins. XII. Sulfated steroid glycosides from the starfish Hacelia attenuata

Three minor sulfated steroidal xylosides were isolated from the Mediterranean starfish H. attenuata. The major one, attenuatoside S-I, contains the aglycon 24-ethyl-5α-cholestane-3β,6β,8,15α,16β,29-hexol; the xylopyranosyl unit is β-glycosidically attached to C(29); the sulfate is at C(15α). The 2nd one, attenuatoside S-II, is the Δ27 analog. Their structures were deduced by spectroscopic methods and confirmed by transformation of desulfated attenuatoside S-II to desulfated attenuatoside S-I. The 3rd compd., attenuatoside S-III, present only in trace amt., is isomeric with attenuatoside S-I in which the primary hydroxyl is apparently at C(26) rather than at C(29). Another asterosaponin, attenuatoside D, contains the novel aglycon 24-northornasterol A [3β,6α,20-trihydroxy-24-nor-5α-cholest-9(11)-en-23-one], 5 sugar units attached by a glycosidic linkage to C(6) of the aglycon and a sulfate group at C(3).