Modular assembly of indole alkaloids enabled by multicomponent reaction

Multisubstituted Indoles by a Dual Gold/Silver-Catalyzed Aminoalkynylation of 2-Alkynylanilines

A straightforward and efficient method for the synthesis of multisubstituted indoles has been developed through a dual gold/silver-catalyzed aminoalkynylation of 2-alkynylanilines using hypervalent iodine(III) reagents under open-air conditions. This approach features the in situ generation of alkynyl Au(III) species, which facilitates the aminoalkynylation of 2-alkynylanilines with excellent functional group tolerance and high yields. Mechanistic studies reveal that the alkynyl gold(III) intermediate plays a crucial role in the reaction pathway. Moreover, the protocol is scalable to gram quantities and offers the potential for further transformation into diverse functionalized compounds.

Perfluoroalkyl Editing of Fluoroalkynes: Chemo-, Regio-, and Stereoselective Synthesis of (E)-(2-Amino-fluoroalkenyl)pyrimidines

A chemo-, regio-, and stereoselective condensation reaction of perfluoroalkyl alkynes (PFAAs), (CH2O)n, and (NH4)2CO3 through the cleavage of five inert C(sp3)-F bonds at three distinct carbon sites, thereby establishing an unprecedented platform for synthesizing structurally unique (E)-(2-amino-fluoroalkenyl)pyrimidines, is first developed. Remarkably, this reaction features mild reaction conditions, good compatibility with various functional groups, excellent E-stereoselectivity, late-stage modification of complex molecules, scalability, and versatile synthetic transformations of the resulting heterocyclic compounds.

Multiomic Analysis Provided Insights into the Responses of Carbon Sources by Wood-Rotting Fungi Daldinia carpinicola

Daldinia carpinicola is a newly identified species of wood-rotting fungi, with substantial aspects of its biology and ecological function yet to be clarified. A Nanopore third-generation sequencer was employed for de novo genome assembly to examine the genetic characteristics. The genome consisted of 35.93 Mb in 46 contigs with a scaffold N50 of 4.384 Mb. Glycoside hydrolases and activities enzymes accounted for a large proportion of the 522 identified carbohydrate-active enzymes (CAZymes), suggesting a strong wood degradation ability. Phylogenetic and comparative analysis revealed a close evolutionary relationship between D. carpinicola and D. bambusicola. D. carpinicola and Hypoxylon fragiforme exhibited significant collinear inter-species genome alignment. Based on transcriptome and metabolomic analyses, D. carpinicola showed a greater ability to utilize sucrose over sawdust as a carbon source, enhancing its growth by activating glycolysis/gluconeogenesis and the citrate cycle. However, compared with sucrose, sawdust as a carbon source activated D. carpinicola amino acid biosynthesis and the production of various secondary metabolites, including diterpenoid, indole alkaloid, folate, porphyrin, and biotin metabolism. The study establishes a theoretical basis for research and applications in biological processes, demonstrating a strategy to modulate the production of secondary metabolites by altering its carbon sources in D. carpinicola.

Multicomponent reactions (MCRs) yielding medicinally relevant rings: a recent update and chemical space analysis of the scaffolds

In this review we have compiled multicomponent reactions (MCRs) that produce cyclic structures. We have covered articles reported since 2019 to showcase the recent advances in this area. In contrast to other available reviews on this topic, we focus specifically on MCRs with strong prospects in medicinal chemistry. Consequently, the reactions operating in a single-pot and yielding novel rings or new substitution patterns under mild conditions are highlighted. Moreover, MCRs that do not require special reagents or catalysts and yield diverse products from commercially available building blocks are reviewed. The synthetic schemes, substrate scope, and other key aspects such as regio- and stereoselectivity are discussed for each MCR. Using cheminformatic tools, we have also attempted to characterize the chemical space of the scaffolds obtained from these MCRs. We show that the MCR scaffolds are novel, more complex, and globular in shape compared to the approved drugs and clinical candidates. Thus, our review represents a step towards identifying and characterizing the novel ring space that can be accessed efficiently through MCRs in a short timeframe.

Combining (CH2O)n and (NH4)2CO3 as a Formamidine Equivalent for "Four-in-One" Synthesis of Fluoroalkylated 2-H-Pyrimidines

Multicomponent reactions hold the potential to maximize the synthetic efficiency in the preparation of diverse and complex molecular scaffolds. An unprecedented formal [3+1+1+1] annulation approach for the one-step synthesis of fluoroalkylated 2-H-pyrimidines commencing from perfluoroalkyl alkenes, paraformaldehyde, and ammonium carbonate is described. By harnessing readily accessible (CH2O)n and cheap (NH4)2CO3 as a formamidine surrogate, this method effectively replaces traditionally preformed amidines with a pyrimidine assembly. The multicomponent reaction proceeds in a step-economical, operationally simple, metal-free, and additive-free manner, featuring a broad substrate scope, excellent functional group compatibility, and scalability. The potential for the synthetic elaboration of the obtained 2-H-pyrimidine is further demonstrated in the alkylation and vinylation of its C2 position.

Iodine-Catalyzed [5 + 1] Carbonylation of 2-Alkenyl/Pyrrolylanilines with CS2 as the Carbonylating Reagent

Novel metal-free iodine (I2)-catalyzed [5 + 1] carbonylation of 2-alkenyl/pyrrolylanilines with carbon disulfide (CS2) as the carbonylating reagent has been developed. This innovative method allows for the synthesis of valuable derivatives such as 4-aryl-2-quinolinones and pyrrolyl-fused quinoxalinones. Notably, this work represents the first instance where CS2 has been utilized as a carbonylating reagent source. The protocol demonstrates the utilization of various substrates, leading to diverse reactions that afford excellent yields under mild conditions. The method also shows good compatibility with functional groups present in the substrates, further enhancing its synthetic utility. Importantly, the developed reaction exhibits scalability, enabling gram-scale synthesis, and shows promise for the synthesis of druglike molecules. In this catalytic system, CS2 serves as the carbonyl source, while dimethyl sulfoxide plays multiple roles, including acting as an oxidant and a solvent. Mechanistic studies have been conducted to elucidate the underlying processes, with the formation of quinolone-2-thiones identified as crucial intermediates, facilitating the carbonylation annulation process.

Discovery of (±)-Penindolenes Reveals an Unusual Indole Ring Cleavage Pathway Catalyzed by P450 Monooxygenase

(±)-Penindolenes A-D (1-4), the first representatives of indole terpenoids featuring a γ-lactam skeleton, were isolated from the mangrove-derived endophytic fungus Penicillium brocae MA-231. Our bioactivity tests revealed their potent antimicrobial and acetylcholinesterase inhibitory activities. The biosynthetic reactions by the five enzymes PbaABCDE leading to γ-lactam ring formation were identified with heterologous expression and in vitro enzymatic assays. Remarkably, the cytochrome P450 monooxygenase PbaB and its homolog in Aspergillus oryzae catalyzed the 2,3-cleavage of the indole ring to generate two keto groups in 1. This is the first example of the oxidative cleavage of indole by a P450 monooxygenase. In addition, rare secondary amide bond formation by the glutamine synthetase-like enzyme PbaD was reported. These findings will contribute to the engineered biosynthesis of unnatural, bioactive indole terpenoids.

A multicomponent reaction for modular assembly of indole-fused heterocycles

Indoles are privileged chemical entities in natural products and drug discovery. Indole-fused heterocycles, particularly seven-membered ones, have received increasing attention due to their distinctive chemical characteristics and wide spectrum of bioactivities. However, the synthetic access to these compounds is highly limited. Herein, we report a unique multicomponent reaction (MCR) for modular assembly of indole-fused seven-membered heterocycles. In this process, indole, formaldehyde and amino hydrochloride could assemble rapidly to yield indole-fused oxadiazepines, and another addition of sodium thiosulphate would furnish indole-fused thiadiazepines. The biological evaluation disclosed the promising anticancer activity of these compounds. Furthermore, this MCR could be applicable in the late-stage and selective modifications of peptides. Therefore, this work provides a powerful strategy for indole functionalization and valuable tool for construction of seven-membered heterocycles.