STEROIDS OF THE MARINE SPONGE CINACHYRA-TARENTINA - ISOLATION OF CHOLEST-4-ENE-3,6-DIONE AND (24R)-24-ETHYLCHOLEST-4-ENE-3,6-DIONE

The MeOH extract of the demospongia Cinachyra tarentina was shown to contain, in addition to three common 3-beta-hydroxysterols and three cholest-4-en-3-ones, two steroids: cholest-4-ene-3,6-dione [1] and (24R)-24-ethylcholest-4-ene-3,6-dione [2], which have not been previously found as naturally occurring compounds. The structures of 1 and 2 have been elucidated by spectroscopic analyses (H-1 and C-13-nmr, uv, ir) and confirmed via synthesis.