Two new indole derivatives from a marine sponge Ircinia sp. collected at Iriomote Island.

Two new indole derivatives, 5-hydroxy-1H-indole-3-carboxylic acid ethyl ester (1) and 5-hydroxy-1H-indole-3-glyoxylate ethyl ester (2), and seven known indole alkaloids, dragmacidonamine B (3), gesashidine A (4), hyrtiosulawesine (5), hyrtiomanzamine (6), hyrtimomine D (7), hyrtiosine A (8), and 5-hydroxy-1H-indole-3-carbaldehyde (9), were isolated from a marine sponge Ircinia sp., Irciniidae, collected at Iriomote Island. The structures of 1 and 2 were elucidated on the basis of their spectroscopic data. Compound 1 has previously been reported as a synthetic intermediate and this is the first time that it has been obtained from a natural source.