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