First model reactions towards the synthesis of sarain A core skeleton based upon a biogenetic scenario

Sarain A is a complex macrocyclic marine alkaloid extracted from sponges of the order Haplosclerida. It is likely that this alkaloid shares a common origin with manzamine alkaloids, also extracted from sponges of the same order. In this paper, new concepts concerning this origin are presented and con-stitute the basis for a synthetic strategy. A preliminary evaluation of this strategy is presented and leads, as a first result, to a five-step access to the bicyclic intermediate 43. (c) Wiley-VCH Verlag GmbH S Co. KGaA, 69451 Weinheim, Germany, 2005).