Agelamasines A and B, diterpene alkaloids from an Okinawan marine sponge Agelas sp.

Two new diterpene alkaloids having an N -methyladenine moiety, agelamasines A ( 1 ) and B ( 2 ), were isolated from an Okinawan marine sponge Agelas sp. The structures of 1 and 2 were elucidated on the basis of spectroscopic analyses. Agelamasine A ( 1 ) is the first diterpene alkaloid with a rearranged (4 → 2)- abeo -clerodane skeleton from a marine source, while agelamasine B ( 2 ) is a clerodane diterpene alkaloid.