Assoanine, pratosine, hippadine, and dehydroanhydrolycorine belong to the pyrrolophenanthridine family of alkaloids, which are isolated from plants of the Amaryllidaceae species. Structurally, these alkaloids are characterized by a tetracyclic skeleton that contains a biaryl moiety and an indole core, and compounds belonging to this class have received considerable interest from researchers in a number of fields because of their biological properties and the challenges associated with their synthesis. Herein, a strategy for the total synthesis of these alkaloids by using C-H activation chemistry is described. The tetracyclic skeleton was constructed in a stepwise manner by C(sp(3))-H functionalization followed by a Catellani reaction, including C(sp(2))-H functionalization. A one-pot reaction involving both C(sp(3))-H and C(sp(2))-H functionalization was also attempted. This newly developed strategy is suitable for the facile preparation of various analogues because it uses simple starting materials and does not require protecting groups.

The synthesis and properties of multifunctional thioureas bearing a variety of functional groups at a position remote from the thiourea moiety are described. A 1,5-disubstituted triazole tether connected with a thiourea and another functional group was synthesized via ruthenium catalyzed Huisgen cycloaddition. We demonstrate the utility of the synthetic thioureas as asymmetric catalysts and probes for the mechanistic elucidation of the course of the Michael reaction of an α,β-unsaturated imide.

A new method has been developed for the stereoselective construction of the AB rings of the quinolizidine skeleton of matrine-type alkaloids with a cis-cis stereochemistry. The key features of this method involve: (i) the construction of the quinolizidine by the reduction of an acylpyridinium cation; and (ii) the late stage introduction of methoxypyridine by sequential Stille coupling and diastereoselective hydrogenation reactions.

A new strategy for synthesizing quinolizidine skeletons by reductive cyclization via acylpyridinium cations was developed. Several functional groups, including carbonyl, silyl, and acetal, were tolerated under mild reaction conditions. The reaction was successfully extended to a one-pot synthesis of a bicyclic compound, and the synthetic strategy was applied to concise total syntheses of quinolizidines 207I and 1-epi-207I, without protecting groups.