Synthetic Study of Dragmacidin E: Enantioselective Construction of the Seven-Membered Ring-Fused Indole Skeleton with Contiguous Stereocenters

Synthesis of 3,4-Fused Pyrroles with Seven-Membered Carbocycles via Cascade C-C σ-Bond Cleavage/Intramolecular Cyclization Reactions

A novel tandem reaction involving amino-substituted ynones and cyclic carbonyls has been developed, efficiently synthesizing 3,4-fused pyrroles with seven-membered carbocycles by a one-pot method. This reaction proceeds through a cascade ring-expansion of cyclic carbonyls, followed by intramolecular cyclization reactions. This metal-free strategy enables the concurrent construction of the medium-sized ring and the pyrrole ring, exhibiting a high step economy.

Recent advances in the synthesis of 3,4-fused tricyclic indoles

The 3,4-fused tricyclic indole framework is a key structural motif in numerous bioactive natural products and pharmaceuticals, thus, it has drawn much attention in synthetic organic chemistry. Synthetic organic chemists have expended substantial effort in developing efficient methods for constructing this privileged molecular framework. In this review, we highlight the advances made in this area, particularly since 2018.

Total Synthesis of Dragmacidins G and H

The total synthesis of dragmacidins G and H was achieved for the first time by employing nucleophilic aromatic substitution and site-selective cross-coupling reactions using appropriately functionalized pyrazines as substrates. The evaluation of antibacterial activities of dragmacidin G, dragmacidin H, and synthetic analogues against Staphylococcus aureus and the efflux pump-deficient Salmonella Typhimurium revealed that the presence of a Br group on the indole ring adjacent to the sulfide unit was important for increasing antibacterial activities.