Biomimetic Assembly Lines Producing Natural Product Analogs: Strategies from a Versatile Manifold to Skeletally Diverse Scaffolds

Rapid and Systematic Exploration of Chemical Space Relevant to Artemisinins: Anti-malarial Activities of Skeletally Diversified Tetracyclic Peroxides and 6-Aza-artemisinins

To achieve both structural changes and rapid synthesis of the tetracyclic scaffold relevant to artemisinins, we explored two kinds of de novo synthetic approaches that generate both skeletally diversified tetracyclic peroxides and 6-aza-artemisinins. The anti-malarial activities of the tetracyclic peroxides with distinct skeletal arrays, however, were moderate and far inferior to artemisinins. Given the privileged scaffold of artemisinins, we next envisioned element implantation at the C6 position with a nitrogen without the trimmings of substituents and functional groups. This molecular design allowed the deep-seated structural modification of the hitherto unexplored cyclohexane moiety (C-ring) while keeping the three-dimensional structure of artemisinins. Notably, this approach induced dramatic changes of retrosynthetic transforms that allow an expeditious catalytic asymmetric synthesis with generation of substitutional variations at three sites (N6, C9, and C3) of the 6-aza-artemisinins. These de novo synthetic approaches led to the lead discovery with substantial intensification of the in vivo activities, which undermine the prevailing notion that the C-ring of artemisinins appears to be merely a structural unit but to be a functional area as the anti-malarial pharmacophore. Furthermore, we unexpectedly found that racemic 6-aza-artemisinin (33) exerted exceedingly potent in vivo efficacies superior to the chiral one and the first-line drug, artesunate.

Combining enyne metathesis with long-established organic transformations: a powerful strategy for the sustainable synthesis of bioactive molecules

This account surveys the current progress on the application of intra- and intermolecular enyne metathesis as main key steps in the synthesis of challenging structural motifs and stereochemistries found in bioactive compounds. Special emphasis is placed on ruthenium catalysts as promoters of enyne metathesis to build the desired 1,3-dienic units. The advantageous association of this approach with name reactions like Grignard, Wittig, Diels–Alder, Suzuki–Miyaura, Heck cross-coupling, etc. is illustrated. Examples unveil the generality of such tandem reactions in providing not only the intricate structures of known, in vivo effective substances but also for designing chemically modified analogs as valid alternatives for further therapeutic agents.

Stereo-controlled synthesis of functionalized tetrahydropyridines based on the cyanomethylation of 1,6-dihydropyridines and generation of anti-hepatitis C virus agents

Densely functionalized tetrahydropyridines were stereoselectively synthesized from 1,6-dihydropyridines. Exploiting a carbonyl group installed at the C3 position of the 1,6-dihydropyridine system, we devised a strategy for cyanomethylation at C2/C6 and subsequent divergent installation of an allyl group at C3/C5 in a highly regio- and stereo-controlled manner. This versatile protocol for programmable functionalization of the 1,6-dihydropyridine system allows the divergent and streamlined synthesis of multiply-substituted tetrahydropyridines as an important class of biologically and medicinally relevant scaffolds. Two of the N-heterocyclic compounds bearing an alkyl nitrile group showed anti-hepatitis C virus (HCV) activity.