Kirkpatrickia- variolosa

The difficult to collect Antarctic sponge, Kirkpatrickia variolosa, is the source of the cytotoxic variolins.300,301 The most active of which, variolin B 18 (Scheme 6.1 Part 2), has shown activity against herpes simplex type I and P388 leukaemia cells. Variolin B induced apoptosis in multidrug resistant leukaemia and epithelial cancer cell lines. Due to the difficulty of Antarctic collection, synthetic efforts have been pursued resulting in the partial synthesis of the tricyclic core of variolin B,306 310 three total syntheses of variolin B311 313 and the development of variolin derivatives.314 317... 

The structures of variolin A (126) and variolin B (127), the alkaloids isolated from the Antarctic sponge Kirkpatrickia variolosa, have been determined <94X3987, 94X3993). Both molecules contain intramolecular hydrogen bonds between C(9)—NH and N-1 and between C(4)—OH and N-3. The C(5 )—O bond length of 1.345 A and the N(U)—Me bond at 1.492 A in (126) are consistent with the unusual zwitterionic character of the pyrimidine substituent. 

Perry, N.B. Ettouati, L. Litaudon, M. Blunt, J.W. Munro, M. H.G. Parkin, S. Hope, H. Alkaloids from Antarctic Sponge Kirkpatrickia variolosa. Part 1 Variolin B, a New Antitumor and Antiviral Compound. Tetrahedron. 1994, 50, 3987-3792. 

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