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.