Sesquiterpenes from Red Alga Laurencia tristicha

Three naturally new sesquiterpenes named 10-hydroxyepiaplysin, 10-hydroxyaplysin and 10-hydroxybromoepiaplysin have been isolated from Laurencia tristicha. On the basis of the spectroscopic techniques their structures were elucidated as (3S, 3αR, 8βS)-(-)-2, 3, 3α, 8β-tetra- hydro-7-bromo-3-hydroxy-3, 3α, 6,8β-tetramethyl-1H-cyclopenta[b]benzofuran, (3R, 3αR, 8βS)- (-)-2,3,3α, 8β-tetrahydro-7-bromo-3-hydroxy-3, 3α,6,8β-tetramethyl-1H-cyclopenta[b]benzofuran and (3S, 3αR, 8βS)-(-)-2, 3,3α,8β-tetrahydro-3-hydroxy-3,3α,6,8β-tetramethyl-1H-cyclopenta[b]- benzofuran, respectively.