Diastereodivergent Synthesis of the Quinolizidine‐Indolizidine Alkaloids of the Leontidine/Camoensine Family

Sparteine Thiourea: The Synthesis of an N Chiral Bispidine-Quinolizidine-Derived Organocatalyst and Applications in Asymmetric Synthesis of Dihydropyrano[c]chromenes

Bispidine, a bridged bicyclic diamine, has been widely utilized as a rigid scaffold in chiral chelating ligands in asymmetric synthesis. In particular, a chiral bispidine-quinolizidine hybrid, such as sparteine, was utilized in asymmetric synthesis involving a metal, exhibiting superior catalytic activity. In this study, we report the design and synthesis of a series of sparteine-derived organocatalysts and the utilization of these catalysts in tandem Michael addition-cyclization reactions. These catalysts have shown excellent catalytic reactivity and enantioselectivity, and the corresponding dihydropyrano[c]chromenes have been prepared in ≤99% yield and ≤99% ee with a low catalyst loading. The recycled catalysts maintain a good catalytic performance even after four cycles, and a gram-scale reaction with a 1% catalyst loading is also performed, providing the product in 96% yield and 98% ee.

Quinolizidine-Type Alkaloids: Chemodiversity, Occurrence, and Bioactivity

Quinolizidine alkaloids (QAs) are nitrogen-containing compounds produced naturally as specialized metabolites distributed in plants and animals (e.g., frogs, sponges). The present review compiles the available information on the chemical diversity and biological activity of QAs reported during the last three decades. So far, 397 QAs have been isolated, gathering 20 different representative classes, including the most common such as matrine (13.6%), lupanine (9.8%), anagyrine (4.0%), sparteine (5.3%), cytisine (6.5%), tetrahydrocytisine (4.3%), lupinine (12.1%), macrocyclic bisquinolizidine (9.3%), biphenylquinolizidine lactone (7.1%), dimeric (7.1%), and other less known QAs (20.9%), which include several structural patterns of QAs. A detailed survey of the reported information about the bioactivities of these compounds indicated their potential as cytotoxic, antiviral, antimicrobial, insecticidal, anti-inflammatory, antimalarial, and antiacetylcholinesterase compounds, involving favorable putative drug-likeness scores. In this regard, research progress on the structural and biological/pharmacological diversity of QAs requires further studies oriented on expanding the chemical space to find bioactive scaffolds based on QAs for pharmacological and agrochemical applications.

Natural Product-Inspired Chiral Ligand Design: Aloperine and N-Substituted Aloperines-Induced Pd-Catalyzed Asymmetric Hydroarylation of Ketimines

A naturally occurring alkaloid aloperine was utilized as a chiral skeleton for the development of new ligands/catalysts in asymmetric synthesis. A number of N-substituted aloperines have been prepared, and a Pd-catalyzed asymmetric hydroarylation of ketimines using these chiral 1,3-diamine ligands was reported. A range of chiral sulfonyl amides were prepared in high yields and enantioselectivities. The stereoselectivity and structure relationships of aloperines have been studied. In addition, preliminary studies on the desymmetrization of meso-anhydride have also shown that these diamines have good potential in organocatalysis. These discoveries would provide a new future development for natural product-inspired chiral ligand design and developments.