Benzastatins E, F, and G: New indoline alkaloids with neuronal cell protecting activity from Streptomyces nitrosporeus

Ligand control of regioselectivity in palladium-catalyzed heteroannulation reactions of 1,3-Dienes

Olefin carbofunctionalization reactions are indispensable tools for constructing diverse, functionalized scaffolds from simple starting materials. However, achieving precise control over regioselectivity in intermolecular reactions remains a formidable challenge. Here, we demonstrate that using PAd2nBu as a ligand enables regioselective heteroannulation of o-bromoanilines with branched 1,3-dienes through ligand control. This approach provides regiodivergent access to 3-substituted indolines, showcasing excellent regioselectivity and reactivity across a range of functionalized substrates. To gain further insights into the origin of selectivity control, we employ a data-driven strategy, developing a linear regression model using calculated parameters for phosphorus ligands. This model identifies four key parameters governing regioselectivity in this transformation, paving the way for future methodology development. Additionally, density functional theory calculations elucidate key selectivity-determining transition structures along the reaction pathway, corroborating our experimental observations and establishing a solid foundation for future advancements in regioselective olefin difunctionalization reactions.

Antiviral Activity of Benzoheterocyclic Compounds from Soil-Derived Streptomyces jiujiangensis NBERC-24992

Pseudorabies virus (PRV) is a pathogen that causes Aujeszky's disease (AD) in animals, leading to huge economic losses to swine farms. In order to discover anti-PRV compounds, we studied the extracts of the strain Streptomyces jiujiangensis NBERC-24992, which showed significant anti-PRV activity. Eight benzoheterocyclic secondary metabolites, including three new compounds (1-3, virantmycins D-G) and five known compounds (4-8, virantmycin, A-503451 D, A-503451 D acetylate, A-503451 A, and A-503451 B), were isolated from the broth of NBERC-24992. The structures of the new compounds were identified by using extensive spectroscopic data, including mass spectrometry (MS), nuclear magnetic resonance (NMR), and electronic circular dichroism (ECD). Compound 1 was found to be a novel heterocyclic compound with a tricyclic skeleton from natural product. All compounds were tested for antiviral activity, and 4 (virantmycin) showed an excellent effect against PRV and was better than ribavirin and acyclovir. Our study revealed that chlorine atom and tetrahydroquinoline skeleton were important active moiety for antiviral activity. Virantmycin could be a suitable leading compound for an antiviral drug against PRV.

Pd-Catalyzed Heteroannulation Using N-Arylureas as a Sterically Undemanding Ligand Platform

We report the development of ureas as sterically undemanding pro-ligands for Pd catalysis. N-Arylureas outperform phosphine ligands for the Pd-catalyzed heteroannulation of N-tosyl-o-bromoanilines and 1,3-dienes, engaging diverse coupling partners for the preparation of 2-subsituted indolines, including sterically demanding substrates that have not previously been tolerated. Experimental and computational studies on model Pd-urea and Pd-ureate complexes are consistent with monodentate binding through the nonsubstituted nitrogen, which is uncommon for metal-ureate complexes.

Anti-cancer and antimicrobial potential of five soil Streptomycetes: a metabolomics-based study

Lack of new anti-cancer and anti-infective agents directed the pharmaceutical research to natural products' discovery especially from actinomycetes as one of the major sources of bioactive compounds. Metabolomics- and dereplication-guided approach has been used successfully in chemical profiling of bioactive actinomycetes. We aimed to study the metabolomic profile of five bioactive actinomycetes to investigate the interesting metabolites responsible for their antimicrobial and anti-cancer activities. Three actinomycetes, namely, Streptomyces sp. SH8, SH10 and SH13, were found to exhibit broad spectrum of antimicrobial activities, whereas isolate SH4 showed the broadest antimicrobial activity against all tested strains. In addition, isolates SH8, SH10 and SH12 displayed potent cytotoxicity against the breast cancer cell line Michigan Cancer Foundation-7 (MCF-7), whereas isolates SH4 and SH12 exhibited potent anti-cancer activity against the hepatoma cell line hepatoma G2 (HepG2) compared with their weak inhibitory properties on the normal breast cells MCF-10A and normal liver cells transformed human liver epithelial-2 (THLE2), respectively. All bioactive isolates were molecularly identified as Streptomyces sp. via 16S rRNA gene sequencing. Our actinobacterial dereplication analysis revealed putative identification of several bioactive metabolites including tetracycline, oxytetracycline and a macrolide antibiotic, novamethymycin. Together, chemical profiling of bioactive Streptomycetes via dereplication and metabolomics helped in assigning their unique metabolites and predicting the bioactive compounds instigating their diverse bioactivities.

Recent Developments in Enantio- and Diastereoselective Hydrogenation of N-Heteroaromatic Compounds

The enantioselective and diastereoselective hydrogenation of N-heteroaromatic compounds is an efficient strategy to access chirally enriched cyclic heterocycles, which often possess highly bio-active properties. This strategy, however, has only been...

Bacterial terpenome

Covering: up to mid-2020 Terpenoids, also called isoprenoids, are the largest and most structurally diverse family of natural products. Found in all domains of life, there are over 80 000 known compounds. The majority of characterized terpenoids, which include some of the most well known, pharmaceutically relevant, and commercially valuable natural products, are produced by plants and fungi. Comparatively, terpenoids of bacterial origin are rare. This is counter-intuitive to the fact that recent microbial genomics revealed that almost all bacteria have the biosynthetic potential to create the C5 building blocks necessary for terpenoid biosynthesis. In this review, we catalogue terpenoids produced by bacteria. We collected 1062 natural products, consisting of both primary and secondary metabolites, and classified them into two major families and 55 distinct subfamilies. To highlight the structural and chemical space of bacterial terpenoids, we discuss their structures, biosynthesis, and biological activities. Although the bacterial terpenome is relatively small, it presents a fascinating dichotomy for future research. Similarities between bacterial and non-bacterial terpenoids and their biosynthetic pathways provides alternative model systems for detailed characterization while the abundance of novel skeletons, biosynthetic pathways, and bioactivies presents new opportunities for drug discovery, genome mining, and enzymology.

Stereogenic cis-2-substituted-N-acetyl-3-hydroxy-indolines via ruthenium(ii)-catalyzed dynamic kinetic resolution-asymmetric transfer hydrogenation

Ruthenium(ii)-catalyzed dynamic kinetic resolution-asymmetric transfer hydrogenation of racemic 2-substituted-N-acetyl-3-oxoindolines to cis-2-substituted-N-acetyl-3-hydroxyindolines is reported. Using the homochiral {Ru[TfDPEN](p-cymene)} catalyst with S/C = 400 in a HCO2H/Et3N mixture, up to >99.9% ee and >99 : 1 dr are obtained with high yields (79-98%). This method provides the first example of preparing enantiomerically pure indolines through asymmetric transfer hydrogenation (ATH).

Facile synthesis of chiral indolines through asymmetric hydrogenation of in situ generated indoles

A concise synthesis of chiral indolines has been developed through intramolecular condensation, deprotection and palladium-catalyzed asymmetric hydrogenation in a one-pot process with up to 96% ee. A strong Brønsted acid played an important role in both the formation of indoles and asymmetric hydrogenation process.

Synthesis of enantiomerically enriched indolines and tetrahydroisoquinolines from (S)-amino acid-derived chiral carbocations: an easy access to (3S,4R)-demethoxy-3-isopropyl diclofensine

Enantiomerically enriched indolines and tetrahydroisoquinolines were synthesized in high yields from easily accessible (S)-amino acid-derived chiral carbocations.

Simple indole alkaloids and those with a non-rearranged monoterpenoid unit

This review covers newly isolated simple indole alkaloids, structure determinations, total syntheses and biological activities reported in the literature in 2003.

Palladium-catalyzed synthesis of N-aryl-2-benzylindolines via tandem arylation of 2-allylaniline: control of selectivity through in situ catalyst modification

A new synthesis of N-aryl-2-benzylindolines from 2-allylanilines and two different aryl bromides is described. This transformation involves two different sequential metal-catalyzed reactions that lead to the formation of two C-N bonds and one C-C bond in a one-pot process. The selective installation of two different aryl groups in these reactions is accomplished by in situ modification of the palladium catalyst prior to addition of the second aryl bromide.

A new indolinepeptide fromPaecilomyces sp. J300

A new indolinepeptide (3) was isolated, together with two known compounds, a cerebroside (1) and an alloxazine (2), from silkworm larvae infected with Paecilomyces sp. J300. On the basis of spectroscopic data, their structures were elucidated as (4E, 8E, 2S, 2'R, 3R)-N-2'-hydroxyhexadecanoyl-1-O-beta-D-glucopyranosyl-9-methyl-4, 8-sphingadienine (1), 7,8-dimethylalloxazine (2) and 3beta,5-dihydroxy-1-N-methyl-indoline-2beta-carbonyl amino-D-alanyl-erythro-beta-hydoxyisoleucinyl-glycine (3).

Total synthesis of (+)-benzastatin E via diastereoselective Grignard addition to 2-acylindoline

[reaction: see text] A stereoselective total synthesis of (+)-benzastatin E (1) is described. The synthesis involves a diastereoselective Grignard addition to 2-acylindoline 2, which is derived from commercially available (S)-2-indolinecarboxylic acid (3). The unknown absolute configuration of (+)-1 is determined as (9S,10R).

The recent impact of solid-phase synthesis on medicinally relevant benzoannelated nitrogen heterocycles

Benzoannelated heterocycles such as benzodiazepines and indoles can be prepared efficiently through cyclization on solid supports, although no single approach is currently universal for the preparation of all benzoannelated N-heterocycle chemistries. In this review, a number of synthetic strategies for the generation of benzoannelated nitrogen heterocycles using resin-bound substrates have been described. Classical heterocycle forming reactions such as the Fischer indole, the Bischler-Napieralski tetrahydroisoquinoline, the Pictet-Spengler tetrahydro-beta-carboline, the Tsuge, the Nenitzescu and the Richter cinnoline reaction are presented. In addition, the Heck, Sonogashira, Wittig, Diels-Alder, and olefin metathesis reactions have been also used. Multicomponent reactions such as the Grieco three-component assembly have been exploited for the synthesis of heterocycles. Cyclative cleavage from the solid support is particularly suitable for the synthesis of heterocycles while particular emphasis has been focused on the synthesis of libraries and the use of combinatorial chemistry techniques. In addition, the most relevant pharmacological properties of benzoannelated nitrogen heterocycles are included.