The pyrrolo[2,1-a]isoquinoline alkaloids

Cascade Synthesis of Pyrrolo[1,2-a]quinolines and Pyrrolo[2,1-a]isoquinolines via Formal [3 + 2]-Cycloaddition of Push-Pull Nitro Heterocycles with Carbonyl-Stabilized Quinolinium/Isoquinolinium Ylides

Various substituted pyrrolo[1,2-a]quinolines and pyrrolo[2,1-a]isoquinolines were synthesized in good to high yields by the Et3N-mediated reaction of push-pull 3-nitrobenzofurans or 1-Ts-/1-Ms-3-nitroindoles and precursors of carbonyl-stabilized quinolinium and isoquinolinium ylides as 1,3-dipole equivalents. These transformations proceed in a one-pot manner starting with the formal [3 + 2]-cycloaddition stage, which is accompanied by double dearomatization of both quinoline/isoquinoline and benzofuran/indole moieties, followed by ring-opening of cyclic intermediate formed and nitrous acid elimination sequence. [3 + 2]-Cycloadducts were isolated as the final products in cases of impossibility or difficulty of their enolization. The present protocol was successfully extended to 3-nitro-4H-chromene derivatives as push-pull dipolarophile component. Finally, using the method of competing reactions, the reactivity of the starting compounds was compared with each other.

Base-Mediated Cascade Lactonization/1,3-Dipolar Cycloaddition Pathway for the One-Pot Assembly of Coumarin-Functionalized Pyrrolo[2,1-a]isoquinolines

An elegant and highly concise strategy for the construction of coumarin-functionalized pyrrolo[2,1-a]isoquinolines from available propargylamines and isoquinolinium N-ylides has been disclosed. In this reaction, isoquinolinium N-ylides acted as a C2 synthon to form a coumarin ring as well as a 1,3-dipole to construct a pyrrole ring in a single pot. This cascade process involves 1,4-conjugate addition/lactonization/1,3-dipolar cycloaddition to construct four chemical bonds (one C-O bond and three C-C bonds) and two new heterocyclic skeletons. Additionally, most of these compounds showed good fluorescence properties and exhibited high molar extinction coefficient and large Stokes shifts.

Antibacterial and Antibiofilm Potential of Ethanolic Extracts of Duguetia vallicola (Annonaceae) against in-Hospital Isolates of Pseudomonas aeruginosa

Pseudomonas aeruginosa is an opportunistic pathogen that is especially dominant in people with cystic fibrosis; the drug resistance expressed by this pathogen and its capacity for adaptation poses a significant challenge to its treatment and control, thereby increasing morbidity and mortality rates globally. In this sense, the search for new treatment alternatives is imminent today, with products of plant origin being an excellent alternative for use. The objective of this research was to evaluate the antibacterial and antibiofilm potential and to explore the possible effect of ethanolic extracts from the wood and bark of Duguetia vallicola on the cell membrane. Microdilution assays showed the inhibition of bacterial growth by more than 50%, with the lowest concentration (62.5 μg/mL) of both extracts evaluated. Furthermore, we report the ability of both extracts to inhibit mature biofilms, with inhibition percentages between 48.4% and 93.7%. Intracellular material leakage experiments (260/280 nm), extracellular pH measurements, and fluorescence microscopy with acridine orange (AO) and ethidium bromide (EB) showed cell membrane damage. This indicates that the antibacterial action of ethanolic extracts of D. vallicola is associated with damage to the integrity of the cell membrane and consequent death of these pathogens. These results serve as a reference for future studies in establishing the mechanisms of action of these extracts.

The old world salsola as a source of valuable secondary metabolites endowed with diverse pharmacological activities: a review

Salsola is an important genus in the plant kingdom with diverse traditional, industrial, and environmental applications. Salsola species are widely distributed in temperate regions and represent about 45% of desert plants. They are a rich source of diverse phytochemical classes, such as alkaloids, cardenolides, triterpenoids, coumarins, flavonoids, isoflavonoids, and phenolic acids. Salsola spp. were traditionally used as antihypertensive, anti-inflammatory, and immunostimulants. They attracted great interest from researchers as several pharmacological activities were reported, including analgesic, antipyretic, antioxidant, cytotoxic, hepatoprotective, contraceptive, antidiabetic, neuroprotective, and antimicrobial activities. Genus Salsola is one of the most notorious plant genera from the taxonomical point of view. Our study represents a comprehensive review of the previous phytochemical and biological research on the old world Salsola secies. It is designed to be a guide for future research on different plant species that still belong to this genus or have been transferred to other genera.

Fused pyrrolo-pyridines and pyrrolo-(iso)quinoline as anticancer agents

This work emphasizes the synthesis strategies and antiproliferative related properties of fused pyrrolo-pyridine (including indolizine and azaindoles) and pyrrolo-(iso)quinoline derivatives recently reported in literature.

One-Pot Synthesis of Chromone-Fused Pyrrolo[2,1-a]isoquinolines and Indolizino[8,7-b]indoles: Iodine-Promoted Oxidative [2 + 2 + 1] Annulation of O-Acetylphenoxyacrylates with Tetrahydroisoquinolines and Noreleagnines

An iodine-promoted one-pot cascade oxidative annulation reaction has been developed for the synthesis of chromone-fused-pyrrolo[2,1-a]isoquinolines and indolizino[8,7-b]indoles from o-acetylphenoxyacrylates, tetrahydroisoquinolines, and noreleagnines. This process underwent a logical approach to both chromone-fused-pyrrolo[2,1-a]isoquinolines and chromone-fused-indolizino[8,7-b]indoles isolamellarin derivatives. Manipulations of l-menthol and dl-α-tocopherol demonstrate the applications of this strategy.

Synthesis and Biological Screening of New Cyano-Substituted Pyrrole Fused (Iso)Quinoline Derivatives

Several new cyano-substituted derivatives with pyrrolo[1,2-a]quinoline and pyrrolo[2,1-a]isoquinoline scaffolds were synthesized by the [3 + 2] cycloaddition of (iso)quinolinium ylides to fumaronitrile. The cycloimmonium ylides reacted in situ as 1,3-dipoles with fumaronitrile to selectively form distinct final compounds, depending on the structure of the (iso)quinolinium salt. Eleven compounds were evaluated for their anticancer activity against a panel of 60 human cancer cell lines. The most potent compound 9a showed a broad spectrum of antiproliferative activity against cancer cell lines representing leukemia, melanoma and cancer of lung, colon, central nervous system, ovary, kidney, breast and prostate cancer. In vitro assays and molecular docking revealed tubulin interaction properties of compound 9a.

One-step route to tricyclic fused 1,2,3,4-tetrahydroisoquinoline systems via the Castagnoli-Cushman protocol

The Castagnoli-Cushman reaction of 3,4-dihydroisoquinolines with glutaric anhydride, its oxygen and sulfur analogues was investigated as a one-step approach to the benzo[a]quinolizidine system and its heterocyclic analogs. An extension towards the pyrrolo[2,1-a]isoquinoline system was achieved with the use of succinic anhydride. The results are evidence of an unexplored method for the access of the aforementioned tricyclic annelated systems incorporating a bridgehead nitrogen atom. The structures and relative configurations of the new compounds were established by means of 1D and 2D NMR techniques. The reactions between 1-methyldihydroisoquinoline and glutaric, diglycolic and succinic anhydrides yielded unexpected isoquinoline derivatives containing an exocyclic double bond. The compounds prepared bear the potential to become building blocks for future synthetic bioactive molecules.

Synthesis of pyrrolidinedione-fused hexahydropyrrolo[2,1-a]isoquinolines via three-component [3 + 2] cycloaddition followed by one-pot N-allylation and intramolecular Heck reactions

Two kinds of [3 + 2] cycloaddition intermediates generated from the three-component reactions of 2-bromobenzaldehydes and maleimides with amino esters or amino acids were used for a one-pot N-allylation and intramolecular Heck reactions to form pyrrolidinedione-fused hexahydropyrrolo[2,1-a]isoquinolines. The multicomponent reaction was combined with one-pot reactions to make a synthetic method with good pot, atom and step economy. MeCN was used as a preferable green solvent for the reactions.

Alkaloids from the stem barks of Erythrina stricta

Four previously undescribed erythrinan alkaloids, 8α-acetonylerythristemine, 8α-acetonylerysotrine, 10β-hydroxy-11β-methoxyerysotramidine and 3-epierysotrine, one undescribed pyrrolidine derivative, S-1-(4-hydroxy-3-methoxyphenethyl)-5-hydroxy pyrrolidin-2-one, and one undescribed amide, N-(3-hydroxy-4-methoxyphenethyl)-4-hydroxylbutanamide, along with thirteen known alkaloids were isolated from the stem barks of Erythrina strica Roxb. (Leguminosae). Their structures were identified by extensive analysis of physical, spectroscopic and spectrometric data. It's very interesting that the coexistence of 3-methoxytyramine, erythrinarbine, S-1-(4-hydroxy-3-methoxyphenethyl)-5-hydroxy pyrrolidin-2-one and N-(3-hydroxy-4-methoxyphenethyl)-4-hydroxylbutanamide that may be closely related in biosynthesis, supports the hypothetical biogenetic pathway of pyrrolo [2,1-a]isoquinoline alkaloids.

Lamellarin alkaloids: Isolation, synthesis, and biological activity

Lamellarins are marine alkaloids containing fused 14-phenyl-6H-[1]benzopyrano[4',3':4,5]pyrrolo[2,1-a]isoquinoline or non-fused 3,4-diarylpyrrole-2-carboxylate ring systems. To date, more than 50 lamellarins have been isolated from a variety of marine organisms, such as mollusks, tunicates, and sponges. Many of them, especially fused type I lamellarins, exhibit impressive biological activity, such as potent cytotoxicity, topoisomerase I inhibition, protein kinases inhibition, and anti-HIV-1 activity. Due to their useful biological activity and limited availability from natural sources, a number of synthetic methods have been developed. In this chapter, we present an updated and comprehensive review on lamellarin alkaloids summarizing their isolation, synthesis, and biological activity.

Pyrrolo[2,1-a]isoquinoline scaffold in drug discovery: advances in synthesis and medicinal chemistry

Pyrrolo[2,1-a]isoquinoline (PIq) is a nitrogen heterocyclic scaffold of diverse alkaloids endowed with several biological activities, including antiretroviral and antitumor activities. Several 5,6-dihydro-PIq (DHPIq) alkaloids, belonging to the lamellarins' family, have proved to be cytotoxic to tumor cells, as well as reversers of multidrug resistance. In this review, we provide an overview of the main achievements over the last decade in the synthetic approaches to access libraries of PIq compounds along with a survey, as comprehensive as possible, of bioactivity, mechanism of action, pharmacophore and structure-activity relationships of synthetic analogs of DHPIq-based alkaloids. The focus is mainly on the potential exploitation of the (DH)PIq scaffold in design and development of novel antitumor drugs.

Pyrrolo[2,1-a]isoquinoline and pyrrole alkaloids from Sinomenium acutum

Two pyrrolo[2,1-a]isoquinolines (1 and 2) and three pyrrole alkaloids (3-5), including three new ones, named sinopyrines A-C (1-3), were isolated from the 95% EtOH extract of the stems and rhizomes of Sinomenium acutum (Thumb.) Rehd. et Wils. The structures of the new compounds were elucidated on the basis of spectroscopic data. This is the first report of pyrrole-bearing natural compounds from the family Menispermaceae.