Ceratinadins D and E, New Bromotyrosine Alkaloids from an Okinawan Marine Sponge Pseudoceratina sp.

Two new bromotyrosine alkaloids, ceratinadins D ( 1 ) and E ( 2 ), were isolated from an Okinawan marine sponge Pseudoceratina sp. as well as a known bromotyrosine alkaloid, psammaplysin F ( 3 ). The gross structures of 1 and 2 were elucidated on the basis of spectroscopic data. The absolute configurations of 1 and 2 were assigned by comparison of the NMR and ECD data with those of a known related bromotyrosine alkaloid, psammaplysin A ( 4 ). Ceratinadins D ( 1 ) and E ( 2 ) are new bromotyrosine alkaloids possessing an 8,10-dibromo-9-methoxy-1,6-dioxa-2-azaspiro[4.6]undeca-2,7,9-trien-4-ol unit with two or three 11- N -methylmoloka'iamine units connected by carbonyl groups, respectively. Ceratinadin D ( 1 ) exhibited antimalarial activities against a drug-resistant and a drug-sensitive strains of Plasmodium falciparum (K1 and FCR3 strains, respectively).