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A synthesis is presented of 2a,8a-syn tricyclic guanidines corresponding to the originally proposed relative configuration of these units of batzelladine F. A description is provided on the preparation of analogous 2a,8a-syn tricyclic guanidines and the evolution of the strategy for the total synthesis of linked tricyclic guanidines corresponding to the proposed constitution and revised relative configuration of batzelladine F.

A new approach to the core structure of the aspidosperma alkaloids that delivers a material in which the ABCE tetracyclic core of aspermidine rapidly assembles, is described. The intramoleuclar [4 + 2]-cycloaddition reactions appear to be very efficient.

A series of model studies was conducted to establish the scope and limitations of intramolecular [4+2] cycloadditions of N-acylated vinglogous ureas with the trienic substrates as a prelude to undertake the total synthesis of the complex manzamine alkaloids. The geometry of the internal double and the presence of an electron-withdrawing group on the diene moiety were essential for the facile and stereoselective formation of the desired cycloadducts.

A diasetreoselective [4 + 2]-annulation of vinyl carbodiimides with chiral N-alkyl imines was developed to access the stereochemically rich polycyclic guanidine cores of the batzelladine alkaloids. Application of this strategy, together with additional steps like long-range directed hydrogenation and diastereoselective intramolecular iodo-amination, led to highly convergent total syntheses of (-)-batzelladine D and (+)-batzelladine A excellent stereocontrol.