Steroid-pyrazine marine alkaloids

When Two Steroids are Better than One The Dimeric Steroid-Pyrazine Marine Alkaloids... 

Ganesan, A., 1996. The dimeric steroid-pyrazine marine alkaloids challenges for isolation, synthesis, and biological studies. Angew. Chem. Int. Ed. Engl 35, 611-615. 

Ganesan, A. (1996) When two steroids are better than one the dimeric steroid-pyrazine marine alkaloids, in Studies in Natural Products Chemistry, vol. 18 (ed. Atta-ur-Rahman), Elsevier Science, Amsterdam, Oxford, New York, pp. 875-906. 

Pettit et al. (24), working on the marine worm Cephalodiscus gilchristi (order Cephalodisicida, phyla Hemichordata, class Pterobranchia) collected from the Indian Ocean off Southeast Africa, have isolated a number of bioactive bis-steroidal pyrazine alkaloids, the cephalostatins 1-15 (11-25). 

Pettit et al., have proposed a biogenetic pathway for the dimeric pyrazine-containing steroidal alkaloids, the cephalostatins isolated from the marine worm Cephalodiscus gilchristi and the tunicate Ritterella tokioka. These alkaloids contain at least 13 fused rings, which constitutes the largest such system known in marine animals. 

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