Quintaquinone, a Merosesquiterpene from the Yellow Sponge cf. Esper.

A chemical investigation of the sponge cf. led to the isolation of 13 merosesquiterpenes, among which quintaquinone (), 5--nakijiquinone L (), and 3-farnesyl-2-hydroxy-5-methoxyquinone () were isolated and reported here for the first time. Particularly, compound is the first member of merosesquiterpenes with a polyketide side chain substituted on C-19. All of the isolated compounds were examined for steroid 5α-reductase inhibitory activity. Cyclospongiaquinone 1 () showed a strong activity in the same range as that of standard finasteride.