An experimental and theoretical investigation of the regio- and stereoselectivity of the polar [3+2] cycloaddition of azomethine ylides to nitrostyrenes

Mechanism and stereoselectivity of a [3 + 2] cycloaddition involving a glucosyl nitrone: a MEDT study

In this study, Molecular Electron Density Theory (MEDT) is employed to investigate the reaction mechanism and the experimentally observed stereoselectivity of the [3 + 2] cycloaddition (32CA) between C-(D-glucoso)-N-methyl nitrone 1 and 1H-pyrrole-2,5-dione 2. Within the Conceptual DFT (CDFT) framework, 2 behaves as an electrophile, while 1 acts as the nucleophile. Bonding Evolution Theory (BET) analysis reveals that this 32CA reaction proceeds through a one-step asynchronous mechanism, where the formation of the C3-C4 bond occurs before that of the O1-C5 bond along both the endo and exo pathways. This asynchronous nature is further supported by analyses based on the Electron Localization Function (ELF) and the Quantum Theory of Atoms in Molecules (QTAIM), which confirm the absence of new disynaptic basins (V(C3,C4) and V(O1,C5)) and of new covalent bonds, respectively. Overall, the endo pathway is found to be both thermodynamically and kinetically more favorable than the exo pathway. Finally, using the distortion/interaction-activation strain model, we demonstrate that the observed endo/exo selectivity is primarily governed by differences in interaction energies. Moreover, molecular docking analyses revealed that the endo product has considerable binding affinity to the 1CIN protease, indicating its potential as a therapeutic inhibitor. Moreover, drug-likeness evaluations verified that the compounds adhere to Lipinski's rule of five, signifying advantageous pharmacokinetic characteristics.

Direct synthesis of N-functionalized indoles through isomerization of azomethine ylides

An unexpected isomerization of azomethine ylides generated in situ from isatin with indoline-2-carboxylic acid has been disclosed, providing direct access to N-functionalized indole scaffolds. This protocol has good functional group tolerance and provides various 3-(1H-indol-1-yl)indolin-2-one derivatives in moderate to high yields simply by using alcohol as the solvent, with no additional additive being required.

Dipolarophile-Controlled Regioselective 1,3-Dipolar Cycloaddition: A Switchable Divergent Access to Functionalized N-Fused Pyrrolidinyl Spirooxindoles

N-fused pyrrolidinyl spirooxindole belongs to a class of privileged heterocyclic scaffolds and is prevalent in natural alkaloids and synthetic pharmaceutical molecules. To realize the switchable synthesis of divergent N-fused pyrrolidinyl spirooxindoles for further biological activity evaluation via a substrate-controlled strategy, a chemically sustainable, catalysis-free, and dipolarophile-controlled three-component 1,3-dipolar cycloaddition of isatin-derived azomethine ylides with diverse dipolarophiles is described in this work. A total of 40 functionalized N-fused pyrrolidinyl spirooxindoles were synthesized in 76-95% yields with excellent diastereoselectivities (up to >99:1 dr). The scaffolds of these products can be well-controlled by employing different 1,4-enedione derivatives as dipolarophiles in EtOH at room temperature. This study provides an efficient strategy to afford a spectrum of natural-like and potentially bioactive N-fused pyrrolidinyl spirooxindoles.

Azomethine Ylides-Versatile Synthons for Pyrrolidinyl-Heterocyclic Compounds

Azomethine ylides are nitrogen-based three-atom components commonly used in [3+2]-cycloaddition reactions with various unsaturated 2π-electron components. These reactions are highly regio- and stereoselective and have attracted the attention of organic chemists with respect to the construction of diverse heterocycles potentially bearing four new contiguous stereogenic centers. This review article complies the most important [3+2]-cycloaddition reactions of azomethine ylides with various olefinic, unsaturated 2π-electron components (acyclic, alicyclic, heterocyclic, and exocyclic ones) reported over the past two decades.

Synthesis of MDM2-p53 Inhibitor BI-0282 via a Dipolar Cycloaddition and Late-Stage Davis–Beirut Reaction

Herein, we report the structure and synthesis of the potent MDM2-p53 inhibitor BI-0282. The complex spirooxindole scaffold bearing four stereocenters embedded in a rigid polycyclic ring-system was effectively prepared on a multi-gram scale in only five synthesis steps employing a three-component 1,3-dipolar cycloaddition and a late-stage Davis–Beirut reaction as key steps.

Antimicrobial Activity and In Silico Molecular Docking Studies of Pentacyclic Spiro[oxindole-2,3′-pyrrolidines] Tethered with Succinimide Scaffolds

Three-component cascade reactions of (E)-3-arylidene-1-methyl-pyrrolidine-2,5-diones, L-valine and various isatin derivatives are described. A series of 17 spiropyrrolidine derivatives with wide structural complexity and diversity have been thus obtained in moderate to excellent yields under mild reaction conditions. The structure and stereochemistry of these N-heterocyclic cycloadducts has been established by spectroscopic techniques and unambiguously confirmed by a single-crystal X-ray diffraction analysis performed on one derivative. UV-visible spectra have been recorded for all new compounds. Furthermore, the synthesized N-heterocyclic compounds have been screened for their in vitro antibacterial and antifungal activities. Several derivatives exhibited moderate to good activities, comparable to those of the known standard drugs Amphotericin B and Tetracycline. Structural activity relationships (SARs) and molecular docking of the most promising derivatives into the binding sites of glucosamine 6-phosphate synthase (GlcN6P) and methionyl-trna-synthetase (1PFV) were also established. Furthermore, pharmacokinetic studies indicate that the heterocycles exhibit acceptable predictive ADMET (absorption, distribution, metabolism, excretion, and toxicity) properties and good drug ability.

A three-component [3 + 2]-cycloaddition/elimination cascade for the synthesis of spirooxindole-pyrrolizines

A three-component synthesis of novel spirooxindole-tetrahydropyrrolizines from secondary α-aminoacids, isatins and vinyl selenones has been disclosed. Products were formed in good yields and high diastereoselectivity by 1,3-dipolar cycloaddition of in situ generated azomethine ylides followed by spontaneous elimination of benzeneseleninic acid. Good regioselectivities with aryl substituted vinyl selenones were observed. The method showed good functional group tolerance, providing a direct approach to biologically relevant spirooxindoles under mild reaction conditions.

Highly regio- and diastereoselective [3 + 2]-cycloadditions involving indolediones and α,β-disubstituted nitroethylenes

A highly diastereoselective [3 + 2]-cycloaddition strategy involving multiple oxindoles and several α,β-disubstituted nitroethylenes is developed to access tetra-substituted α-spiropyrrolidine frameworks. A variety of α-amino acids were employed for the first time in order to generate azomethine ylides under thermal conditions, affording regioisomers 13 and 14 merely by changing the α-substituents (R = H and substituted carbons) of the α-amino acids. The reaction tolerates various sterically demanding, electron-rich and electron-deficient aryl and nitrogen substituents on glycines, oxindoles and nitroethylenes. The operational simplicity, such as the use of a metal-free and non-inert environment, the utilization of non-halogenated solvents and the ease of isolation, adhering to the principles of green chemistry, makes this process attractive for scale-up opportunities. The reaction delivers good yields (80-94%) and diastereoselectivities (up to 98 : 2) in favor of (cis,cis)-spirooxindoles, with opposite regioselectivity compared to β-nitrostyrenes under identical conditions. Two spiropyrrolidine cycloadducts with unprotected amides exhibited significant activity against Gram-positive MRSA.

Highly diastereoselective construction of novel dispiropyrrolo[2,1-a]isoquinoline derivativesviamulticomponent 1,3-dipolar cycloaddition of cyclic diketones-based tetrahydroisoquinoliniumN-ylides

In the quest for new heterocyclic scaffolds exhibiting potentially biological activities for medicinal chemistry, a multicomponent 1,3-dipolar cycloaddition reaction of tetrahydroisoquinolinium N-ylides, generated in situ from cyclic diketones and isoquinoline, and (E)-3-arylidene-1-phenyl-pyrrolidine-2,5-diones has been developed. This route provides workable access to dispiropyrrolo[2,1-a]isoquinoline-fused pyrrolidine-2,5-diones bearing two adjacent spiro-carbons. An unprecedented regioselectivity was observed in this 1,3-dipolar cycloaddition, leading to the construction of a novel dispirooxindole skeleton. The structure and relative stereochemistry of the spiranic adducts have been confirmed by three X-ray diffraction studies. To reinforce the observed regio- and stereoselectivity of the [3+2] cycloaddition, calculations using the DFT approach at the B3LYP/6-31G(d,p) level were carried out. It was found that this reaction affords the kinetic products.

A new series of dispiropyrrolo[2,1-a]isoquinoline derivatives was synthesized by multicomponent 1,3-dipolar cycloaddition reaction of tetrahydroisoquinolinium N-ylides and (E)-3-arylidene-1-phenyl-pyrrolidine-2,5-diones.

Discovery of Novel Spiro[3H-indole-3,2'-pyrrolidin]-2(1H)-one Compounds as Chemically Stable and Orally Active Inhibitors of the MDM2-p53 Interaction

Scaffold modification based on Wang's pioneering MDM2-p53 inhibitors led to novel, chemically stable spiro-oxindole compounds bearing a spiro[3H-indole-3,2'-pyrrolidin]-2(1H)-one scaffold that are not prone to epimerization as observed for the initial spiro[3H-indole-3,3'-pyrrolidin]-2(1H)-one scaffold. Further structure-based optimization inspired by natural product architectures led to a complex fused ring system ideally suited to bind to the MDM2 protein and to interrupt its protein-protein interaction (PPI) with TP53. The compounds are highly selective and show in vivo efficacy in a SJSA-1 xenograft model even when given as a single dose as demonstrated for 4-[(3S,3'S,3'aS,5'R,6'aS)-6-chloro-3'-(3-chloro-2-fluorophenyl)-1'-(cyclopropylmethyl)-2-oxo-1,2,3',3'a,4',5',6',6'a-octahydro-1'H-spiro[indole-3,2'-pyrrolo[3,2-b]pyrrole]-5'-yl]benzoic acid (BI-0252).

Synthesis and biological evaluation of new spirooxindoles with embedded pharmacophores

The newly synthesized spirooxindole derivatives have shownin vitroantioxidant, antidiabetic and acetylcholinesterase inhibitory activities.

Molecular diversity of spirooxindoles. Synthesis and biological activity

Spirooxindoles are important synthetic targets possessing extended biological activity and drug discovery applications. This review focuses on the various strategies for the enantioselective synthesis of spirocyclic oxindoles relying on reports over the past decade and from earlier work. The spirooxindoles in this review are separated into three structural classes, and then further categorized into the method type from which the spirocycle is generated.

A strategic approach to the synthesis of functionalized spirooxindole pyrrolidine derivatives: in vitro antibacterial, antifungal, antimalarial and antitubercular studies

A series of spirooxindole pyrrolidine derivatives has been synthesized and evaluated for theirin vitrobiological activities. The observed regio- and stereoselectivity of the cycloaddition reaction has been rationalized using DFT calculations.

An experimental and theoretical study on the regioselective synthesis of a new class of spiropyrrolothiazoles with quinoxaline motifs via a 1,3-dipolar cycloaddition reaction. An evaluation of DFT methods

Evaluation of B3LYP/6-31G(d,p), wB97xD/6-31G(d,p) and M06-2X/6-31G(d,p) methods revealed the importance of π/π interactions in regio- and stereoselectivity of cycloaddition reactions.

Acetic acid promoted tandem cyclization of in situ generated 1,3-dipoles: stereoselective synthesis of dispiroimidazolidinyl and dispiropyrrolidinyl oxindoles with multiple chiral stereocenters

Acetic acid catalyzed in situ generation of ketimine based 1,3-dipoles, and single-step construction of imidazolidine ring with three chiral centers and pyrrolidine ring with four chiral centers via formation of new C–N and C–C bonds is reported.

Synthesis of functionalized dispiro-oxindoles through azomethine ylide dimerization and mechanistic studies to explain the diastereoselectivity

Synthesis of functionalized dispiro-oxindoles via [3 + 3]-cycloaddition of azomethine ylide generated from condensation of isatin and proline is reported. A transition state model for the origin of diastereoselectivity and mechanism of formation of these types of adducts is proposed.