Erythrina type

Only 3 of the 12 species of Cocculus (Menispermaceae) have been examined for alkaloids and most studies have concerned C. laurifolius, which has yielded the greatest number of alkaloids (see Table I) (57, 55-58, 60, 69-76). The Erythrina-type alkaloids obtained from Cocculus are abnormal in the sense that they contain no oxygen function at C-16, the only exceptions being dihydroerysovine (44), dihydroerysodine (47), and erythroculine (53). Erythroculine is, however, unusual in that it has a methoxycarbonyl group at C-16. The two alkaloids isococculidine (36) and isococculine (37) are of theA2(l)-alkene type rather than the Al(6)-alkene type. 

This section will discuss the Cephalotaxine [e.g., (23)] and the Homoerythrina [e.g., (19)] alkaloids as well as the normal Erythrina types/ The last two groups are clearly biogenetically related while the Cephalotaxine structure may be regarded as a rearranged Erythrina skeleton. 

C. laurifolius also produces coccuvine (35), an alkaloid of the Erythrina type. The biosynthesis of this alkaloid had... 

Cephalotaxine.—Cephalotaxine (122) is an abundant alkaloid of Cephalotaxus species. The natural co-occurrence of cephalotaxine and alkaloids of the homo-erythrina type, e.g. 3-epischelhammericine (123), suggested that these two alkaloid... 

Synthesis Pathways to Erythrina Alkaloids and Erythrina Type Compounds... 

The erythrina-type alkaloids are characterized by their unique tetracyclic spiroamine framework. They are generally classified into two main groups Alkaloids predominantly possessing a 6-5-6-6-membered indoloisoquinoline core are called erythrinanes and those exhibiting a 6-5-7-6-membered indolobenzazepine skeleton are generally called schelhammeranes or homoerythrinane alkaloids (see Fig. 1). 

Amer ME, Shamma M, Freyer AJ (1991) The Tetracyclic Erythrina Alkaloids. J Nat Prod 54 329 (A compilation of ca. 90 erythrina-type alkaloids together with their spectral data)... 

An optimized one pot procedure was established, and the Erythrina -type compound 82 was obtained in 82% isolated yield after an oxidative carbon -carbon coupling (FIFA) followed by a Michael addition (K2CO3) in trifluoroethanol. 

Manteca, L Sotomayor, N. Villa, M.-J. Lete, E. Tandem carbophilic addition-N-acyliminium ion cyclization for the synthesis of functionalized pyrrolo[2,l-a]isoquinolones Key intermediates for the preparation of Erythrina -type alkaloids. Tetrahedron Lett., 1996, 37, 7841-7844. 

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