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Concise construction of the tetracyclic core of lycorine-type alkaloids and the formal synthesis of α-lycorane based on asymmetric bifunctional thiourea-catalyzed cascade reaction.

A concise and stereoselective construction of the tetracyclic core of lycorine-type alkaloids and the formal synthesis of α-lycorane has been achieved. The feature of the current method is the employment of a bifunctional thiourea-catalyzed cascade reaction as a powerful tool to construct the skeleton of the natural product, which is a challenging yet very rarely explored strategy. As a result, the tetracyclic core is efficiently synthesized in just three simple operations involving two consecutive cascade reactions.