The Saraine Alkaloids.

Saraines have been isolated by the group of Cimino from the marine sponge Reniera sarai collected in the Bay of Naples. These alkaloids can be classified into two categories, depending on the type of their structure. Saraines 1-3 and isosaraines 1-3 are characterized by a trans-2-oxoquinolizidine moiety bound directly to a tetrahydropyridine ring, both nuclei being also linked by two alkyl chains of different lengths. On the other hand, saraines A-C and misenine present a diazatricyclic central core, showing an unusual interaction between an aldehyde and a tertiary amine and giving them a zwitterionic character, and flanked with two chains forming macrocycles. In a first part of the chapter, the isolation, spectral data, and structure elucidation of saraines are presented. Biological properties and biogenetic proposals concerning these compounds are then described. The most important part is devoted to synthetic approaches and total synthesis of saraine A.