The Catalyst-Controlled Divergent Cascade Reactions of Homo-Propargylic Amines and Nitrones: Synthesis of Pyrrolo-Isoxazolidines and γ-Lactams

Inhibitory Activity of Pyrroloisoxazolidine Derivatives against Chlamydia trachomatis

The obligate intracellular bacterium Chlamydia trachomatis is a group of worldwide human pathogens that can lead to serious reproductive problems. The frequent clinical treatment failure promoted the development of novel antichlamydial agents. Here, we firstly reported a group of pyrroloisoxazolidine-inhibited C. trachomatis in a dose-dependent manner in vitro. Among them, compounds 1 and 2 exhibited the strongest inhibitory activity with IC₅₀ values from 7.25 to 9.73 μM. The compounds disturbed the whole intracellular life cycle of C. trachomatis, mainly targeting the middle reticulate body proliferation stages. Besides, the compounds partially inhibited the chlamydial infection by reducing elementary body infectivity at high concentration. Our findings suggest the potential of pyrroloisoxazolidine derivatives as promising lead molecules for the development of antichlamydial agents.

Synthesis of the Hexahydropyrrolo-[3,2-c]-quinoline Core Structure and Strategies for Further Elaboration to Martinelline, Martinellic Acid, Incargranine B, and Seneciobipyrrolidine

Natural products are rich sources of interesting scaffolds possessing a plethora of biological activity. With the isolation of the martinella alkaloids in 1995, namely martinelline and martinellic acid, the pyrrolo[3,2-c]quinoline scaffold was discovered. Since then, this scaffold has been found in two additional natural products, viz. incargranine B and seneciobipyrrolidine. These natural products have attracted attention from synthetic chemists both due to the interesting scaffold they contain, but also due to the biological activity they possess. This review highlights the synthetic efforts made for the preparation of these alkaloids and formation of analogues with interesting biological activity.

Enamides and dienamides in phosphoric acid-catalysed enantioselective cycloadditions for the synthesis of chiral amines

This feature article describes how enamides and dienamides can participate in chiral phosphoric acid catalyzed enantioselective cycloadditions to prepare a wide range of cyclic amines.

Copper-Catalyzed Cascade Cyclization of Indolyl Homopropargyl Amides: Stereospecific Construction of Bridged Aza-[n.2.1] Skeletons

Catalytic cycloisomerization-initiated cascade cyclizations of terminal alkynes have received tremendous interest, and been widely used in the facile synthesis of a diverse array of valuable complex heterocycles. However, these tandem reactions have been mostly limited to noble-metal catalysis, and are initiated by an exo-cyclization pathway. Reported herein is an unprecedented copper-catalyzed endo-cyclization-initiated tandem reaction of indolyl homopropargyl amides, where copper catalyzes both the hydroamination and Friedel-Crafts alkylation process. This method allows the practical and atom-economical synthesis of valuable bridged aza-[n.2.1] skeletons (n=3-6) with wide substrate scope, and excellent diastereoselectivity and enantioselectivity by a chirality-transfer strategy. Moreover, the mechanistic rationale for this novel cascade cyclization is also strongly supported by control experiments, and is distinctively different from the related gold catalysis.

Temperature-Controlled Divergent Hydroamination Cyclization [2+2]-Cycloaddition Cascade Reactions of Homopropargylic Amines with 2-Butynedioates: Direct Access To Pyrrolo- b-cyclobutene and Dihydro-1 H-azepines

The diversified temperature-controlled hydroamination cyclization cascade reactions of homopropargylic amines and 2-butynedioates were developed for the construction of various pyrrolo- b-cyclobutenes and dihydro-1 H-azepines, respectively. This reaction actually involved an intramolecular hydroamination cyclization of homopropargylic amines to give the active dihydropyrroles intermediates, which subsequently underwent [2+2]-cycloaddition with 2-butynedioates to generate the pyrrolo- b-cyclobutenes at no more than 120 °C. Alternatively, the dihydro-1 H-azepines were directly produced at 150 °C in the reactions of homopropargylic amines and 2-butynedioates. The application of substrate scope was wide, and the corresponding products were obtained in high to excellent yields.

Metal-free multicomponent cascade reactions of homopropargylic amines and acyl chlorides as well as potassium thiocyanate and diiodine: an access to thiazine imides

A novel metal-free multicomponent cascade reaction was developed for the construction of thiazine imides. This four-component cascade reaction had advantages of mild reaction conditions, wide substrate scope and good atom economy. Four new bonds were formed in one pot via a 6-exo-dig iodothiolation cyclization of homopropargylic amines. The corresponding E-configurational thiazine imide products possess an exocyclic vinyliodide functional group.

Ag(i)-Catalyzed solvent-free CO2 capture with homopropargylic amines: an efficient access to 1,3-oxazinan-2-ones

An efficient solvent-free CO₂ capture and transformation method was developed through using homopropargylic amines in the presence of AgOAc and DBU, and a series of 1,3-oxazinan-2-ones was obtained in excellent yields.