New Δ8(14)-3β,7α-dihydroxysterols from the marine sponge Pellina semitubulosa

The marine spone Pellina semitubulosa was examined for polyoxygenated sterols. The sponge contained six new 3β,7α-diols, (22E)-5α-cholesta-8(14),22-diene-3β,7α-diol [2], (22E,24R)-24-methyl-5α-cholesta-8(14),22-diene-3β,7α-diol [3], (22E,24S)-24-methyl-5α-cholesta-8(14),22-diene-3β,7α-diol [4], 24-methyl-5α-cholesta-8(14),24(28)-diene-3β,7α-diol [5], (24Z)-24-ethyl-5α-cholesta-8(14),24(28)-diene-3β,7α-diol [6], and (24E)-24-ethyl-5α-cholesta-8(14),24(28)-diene-3β,7α-diol [7], along with the previously synthesized 5α-cholest-8(14)-ene-3β,7α-diol [1]. The structure of the new natural products was determined by interpretation of spectral data and secured by synthesis of 1 starting from 5α-cholest-7-en-3β-ol