Three New Tricyclic Guanidine Alkaloids from the Sponge Batzella sp.

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 ).