Sarcotragins A (1) and B (2), two terpenoid alkaloids of an unusual structural class, have been isolated from the sponge Sarcotragus sp. collected from Jaeju Island, Korea. The structures of these compounds have been determined as lineal trisnorsesterterpenes containing a phenethylamine lactam or the corresponding glycine lactam moiety by combined chemical and spectral methods. (C) 2001 Elsevier Science Ltd. All rights reserved.