Lamellarin alkaloids

Following the communcation in 2004, a full report appeared that described type Ilac cyclocondensation reactions between dihydroisoquinolines and a-nitrocinnamates leading to complex fused pyrroles <06JOC9440>. The latter were converted into the lamellarin alkaloids and related analogues. 

Ishibashi and coworkers [26] have reported a very efficient method for synthesizing a variety of lamellarin alkaloids and the preparation of lamellarin D and H are presented in Scheme 8. 

Davis, R.A. Carroll, A.R. Pierens, G.K. Quinn, R.J. (1999A)New lamellarin alkaloids from the Australian ascidian, Didemnum chartaceum. J. Nat. Prod., 62, 419-24. 

Both AgOTf and AgSbF6 (10mol%) were the best catalysts for this transformation, and the reaction was conducted in the presence of an hindered base, 2,6-di-tert-butyl-4-methylpyridine (DTBMP). The azomethine ylide CC intermediate has been identified in a test reaction in the absence of DMAD, via mass spectrometry. The scope and limitations have been thoroughly studied for reaching pyrroloisoquinoline scaffold, which is a substructure of the lamellarin alkaloid family. 

A solid-phase synthesis of the lamellarin alkaloids Q and O featured the preparation of scaffold 79 and subsequent Suzuki coupling [24]. Dibromopyrrole 78 was synthesized as shown earlier for 14. 

A type Ib cyclization involving ketene-iV,S-acetals led to the formation of highly functionalized pyrroles including 4-acetylpyrrole-2-carboxylates <05SC693> and 3,4-diarylpyrroles <05TL475>. The latter are useful building blocks for the preparation of the lamellarin alkaloids. Another approach to the lamellarin framework involved a 1,5-electrocyclization of azomethine ylides <05TL7531>. 

New potent cytotoxic lamellarin alkaloids from Indian ascidian Didemnum obscurum. Tetrahedron 61, 9242-9247. 

Recent advances in lamellarin alkaloids isolation, synthesis and activity. Pla, D., Albericio, F., Alvarez, M. (2008), 8, 746-760. 

Reddy, S.M., Srinivasulu, M., Satyanarayana, N., Kondapi, A.K., and Venkateswarlu, Y. (2005) New potent cytotoxic lamellarin alkaloids from Indian ascidian Didemnum obscumm. Tetrahedron, 61, 9242— 9247. 

Krishnaiah, P., Reddy, V.L.N., Venkataramana, G., Ravinder, K., Srinivasulu, M., Raju, TV, Ravikumar, K., Chandrasekar, D., Ramakrishna, S., and Venkateswarlu, Y. (2004) New lamellarin alkaloids from the Indian ascidian Didemnum obscurum and their antioxidant properties./. Nat. Prod., 67, 1168-1171. 

Ruchirawat, S. and Mutarapat, T. (2001) An efficient synthesis of lamellarin alkaloids synfiiesis of lamellarin G trimethyl ether. 

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