3 NEW TRICYCLIC GUANIDINE ALKALOIDS FROM THE SPONGE BATZELLA SP

During the large-scale isolation of the batzelladines A and B, which a re inhibitors of gp120-CD4 binding, we isolated 19 minor guanidine alk aloids. Three new tricyclic guanidine alkaloids isolated from this gro up were named 8a,8b-dehydroptilocaulin (2), 8a,8b-dehydro-8-hydroxypti locaulin (3), and 1,8a;8b,3a-didehydro-8-hydroxyptilocaulin (5). The r ecently described mirabilin B (4) was also isolated. The structures an d relative stereochemistry of these compounds were determined by spect ral analysis and by comparison with spectral data of ptilocaulin (1).