Reniera sarai Sarains

The Mediterranean sponge Reniera sarai is a rich source of new macro-cyclic alkaloids, named sarains, which may be biogenetically related to petrosin (246) or araguspongins (236-243). The structures of sarains 1-3 (247-249) (2/0) and isosarain 1 (250) (211) were clarified on the basis of extensive spectroscopic analyses. The position of the double bond in 249 remains to be determined. The more polar fraction of this sponge contained three UV-absorbing alkaloids, named sarains A-C. The structure of the diacetylated derivative of sarain A (251) was established by X-ray analyis (2/2). 

Sarains, a new class of alkaloids from the sponge Reniera sarai. Cimino, G. De Stefano, S. Scognamiglio, G. and Trivellone, E. Bull. Soc. Chim. Belg. 1986, 95, 783. 

Further studies of alkaloids from Reniera sarai structures of saraine-3 and isosaraine-3 absolute stereochemistry of saraine-1 and sariane 2. Guo, Y. Madaio, A. Trivellone, E. Scognamiglio, G. and Cimino, G. Tetrahedron, 1996, 52, 14961. 

Unprecedented alkaloid from the mediterranean sponge Reniera sarai X-ray structure of an acetate derivative of Sarain-A. Cimino, G. Mattia, C. A. Mazzarella, L. Puliti, R. Scognamiglio, G. Spinella, A. and Trivellone, E. Tetrahedron 1989, 45, 3863. 

Sarain A (12) (Fig. 5) was isolated by Cimino et al. from the sponge Reniera sarai in 1989 [57] and has a unique 2,8-diazatricyclo[5.4.0.0 Mmidecane skeleton in which the tertiary amine of a pyrrolidine ring (ring B) interacts with an adjacent aldehyde. 

Guo, Y.W., Madaio, A., Trivellone, E., Scognamiglio, G., and Cimino, G. (1996a) Structural and stereochemical studies of saraines macrocyclic alkaloids of the sponge Reniera sarai. Tetrahedron, 52, 8341-8348. 

In Scheme 5.46, the syntheses of different macrocyclic natural products classified as alkaloids are summarized. The rich variety of biological activities associated with both plant-derived and animal-derived alkaloids has stimulated many organic synthetic groups. The main problem from a metathesis point of view is the abihty of the nitrogen to coordinate to metal-alkyhdene complexes and to interfere unpro-ductively with the catal)rtic activity. In the examples summarized herein, the use of [Ru]-I, [Ru]-II, and [Ru]-V has proven to be effective. Consequently, (—)-sarain A (189) (Equation 1, Scheme 5.46), isolated from sponge Reniera sarai [81] ircinal... 

---