A Multicomponent Protocol for the Synthesis of Highly Functionalized γ-Lactam Derivatives and Their Applications as Antiproliferative Agents

In Silico Analysis: Anti-Inflammatory and α-Glucosidase Inhibitory Activity of New α-Methylene-γ-Lactams

The research about α-methylene-γ-lactams is scarce; however, their synthesis has emerged in recent years mainly because they are isosters of α-methylene-γ-lactones. This last kind of compound is structurally most common in some natural products' nuclei, like sesquiterpene lactones that show biological activity such as anti-inflammatory, anticancer, antibacterial, etc., effects. In this work, seven α-methylene-γ-lactams were evaluated by their inflammation and α-glucosidase inhibition. Thus, compounds 3-methylene-4-phenylpyrrolidin-2-one (1), 3-methylene-4-(p-tolyl)pyrrolidin-2-one (2), 4-(4-chlorophenyl)-3-methylenepyrrolidin-2-one (3), 4-(2-chlorophenyl)-3-methylenepyrrolidin-2-one (4), 5-ethyl-3-methylene-4-phenylpyrrolidin-2-one (5), 5-ethyl-3-methylene-4-(p-tolyl)pyrrolidin-2-one (6) and 4-(4-chlorophenyl)-5-ethyl-3-methylenepyrrolidin-2-one (7) were evaluated via in vitro α-glucosidase assay at 1 mM concentration. From this analysis, 7 exerts the best inhibitory effect on α-glucosidase compared with the vehicle, but it shows a low potency compared with the reference drug at the same dose. On the other side, inflammation edema was induced using TPA (12-O-tetradecanoylphorbol 13-acetate) on mouse ears; compounds 1-7 were tested at 10 µg/ear dose. As a result, 1, 3, and 5 show a better inhibition than indomethacin, at the same doses. This is a preliminary report about the biological activity of these new α-methylene-γ-lactams.

A Highly Efficient Strategy for One-Pot and Pseudo-Six-Component Synthesis of Hexahydroquinolines

In this study, a homogeneous acid-catalyzed reaction of a series of benzaldehydes, benzylamines, and Meldrum's acid was presented, allowing the novel one-pot and multicomponent synthesis of hexahydroquinolines with high stereoselectivity. The current strategy has advantages including high regioselectivity, good efficiency, reasonable diversity, utilization of an inexpensive and safe catalyst, and easy purification of products by simple recrystallization. The current reaction utilizes 2 equiv of Meldrum's acid, 3 equiv of benzaldehyde derivatives, and one equiv of amine derivatives to yield (4'S,5'S,7'S)-1'-benzyl-2,2-dimethyl-4',5',7'-triphenyl-3',4',7',8'-tetrahydro-1'H-spiro[[1,3]dioxane-5,6'-quinoline]-2',4,6(5'H)-trione derivatives.

Nickel-Catalyzed Aminofluoroalkylative Cyclization of Styrenes with Ethyl Fluoroacetate and Anilines toward Fluoro-γ-Lactams

A novel method for the nickel-catalyzed multicomponent aminofluoroalkylation/cyclization of styrenes with ethyl fluoroacetate and anilines has been developed. This protocol provides general and efficient access to a diverse range of fluoro-γ-lactams from simple and readily available starting materials. Control experiments prove the involvement of radical intermediates and excluded the presence of 2-fluoro-N-phenylacetamide.

Synthesis of Trifluoromethylated γ-Lactams through Radical Cascades of N-Cyano Alkenes with CF3SO2Na

We report herein a facile strategy to synthesize trifluoromethylated γ-lactams through trifluoromethylcarbonylation of N-cyano alkenes using readily available CF₃SO₂Na as the CF₃ radical source. A range of trifluoromethyl-containing γ-lactams was obtained in good yields. This transition-metal-free protocol is demonstrated with mild conditions, broad substrate scope, good functional group tolerance, convenient reagents, and an easy-to-handle operating system.

Synthesis of Tetrasubstituted Phosphorus Analogs of Aspartic Acid as Antiproliferative Agents

An efficient general method for the synthesis of a wide family of α-aminophosphonate analogs of aspartic acid bearing tetrasubstituted carbons is reported through an aza-Reformatsky reaction of α-iminophosphonates, generated from α-aminophosphonates, in an umpolung process. In addition, the α-aminophosphonate substrates showed in vitro cytotoxicity, inhibiting the growth of carcinoma human tumor cell lines A549 (carcinomic human alveolar basal epithelial cell) and SKOV3 (human ovarian carcinoma). In view of the possibilities in the diversity of the substituents that offer the synthetic methodology, an extensive profile structure-activity is presented, measuring IC₅₀ values up to 0.34 µM in the A549 and 9.8 µM in SKOV3 cell lines.

Experimental and theoretical studies on the synthesis of 1,4,5-trisubstituted pyrrolidine-2,3-diones

Substituted 4-acetyl-3-hydroxy-3-pyrroline-2-ones have been prepared via three-component reactions and the tautomerism of these 3-pyrroline-2-ones is due to the slight difference of energy, and the significantly large rate constant of transformation between two tautomers. 1,4,5-Trisubstituted pyrrolidine-2,3-dione derivatives were prepared from the above mentioned 2-pyrrolidinone derivatives and aliphatic amines, which exist in enamine form and are stabilized by an intramolecular hydrogen bond. A possible reaction mechanism between 3-pyrroline-2-one and aliphatic amine (CH₃NH₂) was proposed based on computational results and the main product is formed favorably following the PES via the lowest ΔG^# pathway in both the gas-phase and an ethanol solvent model. DFT calculations showed that kinetic selectivity is more significant than thermodynamic selectivity for forming main products.

Exploring the Synthetic Potential of γ-Lactam Derivatives Obtained from a Multicomponent Reaction. Applications as Antiproliferative Agents

A study on the reactivity of 3-amino α,β-unsaturated γ-lactam derivatives obtained from a multicomponent reaction is presented. Key features of the substrates are the presence of an endocyclic α,β-unsaturated amide moiety and an enamine functionality. Following different synthetic protocols, the functionalization at three different positions of the lactam core is achieved. In the presence of a soft base, under thermodynamic conditions, the functionalization at C-4 takes place where the substrates behave as enamines, while the use of a strong base, under kinetic conditions, leads to the formation of C-5-functionalized γ-lactams, in the presence of ethyl glyoxalate, through a highly diastereoselective vinylogous aldol reaction. Moreover, the nucleophilic addition of organometallic species allows the functionalization at C-3, through the imine tautomer, affording γ-lactams bearing tetrasubstituted stereocenters, where the substrates act as imine electrophiles. Taking into account the advantage of the presence of a chiral stereocenter in C-5 substituted γ-lactams, further diastereoselective transformations are also explored, leading to novel bicyclic substrates holding a fused γ and δ-lactam skeleton. Remarkably, an example of a highly stereoselective formal [3+3] cycloaddition reaction of chiral γ-lactam substrates is reported for the synthesis of 1,4-dihidropyridines, where a non-covalent attractive interaction of a carbonyl group with an electron-deficient arene seems to drive the stereoselectivity of the reaction to the exclusive formation of the cis isomer. In order to unambiguously determine the substitution pattern resulting from the diverse reactions, an extensive characterization of the substrates is detailed through 2D NMR and/or X-ray experiments. Likewise, applications of the substrates as antiproliferative agents against lung and ovarian cancer cells are also described.

Multicomponent Synthesis of Unsaturated γ-Lactam Derivatives. Applications as Antiproliferative Agents through the Bioisosterism Approach: Carbonyl vs. Phosphoryl Group

We report efficient synthetic methodologies for the preparation of 3-amino and 3-hydroxy 3-pyrrolin-2-ones (unsaturated γ-lactams) through a multicomponent reaction of amines, aldehydes and acetylene or pyruvate derivatives. The densely substituted γ-lactam substrates show in vitro cytotoxicity, inhibiting the growth of the carcinoma human tumor cell lines RKO (human colon epithelial carcinoma), SKOV3 (human ovarian carcinoma) and A549 (carcinomic human alveolar basal epithelial cell). In view of the possibilities for the diversity of the substituents that offer a multicomponent, synthetic methodology, an extensive structure–activity profile is presented. In addition, the bioisosteric replacement of the flat ester group by a tetrahedral phosphonate or phosphine oxide moiety in γ-lactam substrates leads to increased growth inhibition activity. Cell morphology analysis and flow cytometry assays indicate that the main pathway by which our compounds induce cytotoxicity is based on the activation of the intracellular apoptotic mechanism.

An overview of the applications of chiral phosphoric acid organocatalysts in enantioselective additions to CO and CN bonds

Since 2004, chiral phosphoric acids (CPAs) have emerged as highyl efficient organocatalysts, providing excellent results in a wide reaction scope. In this review, the applications of CPA for enantioselective additions to CO and CN bonds are covered.

Synthesis and evaluation of the antioxidant activity of 3-pyrroline-2-ones: experimental and theoretical insights

The heterocyclic γ-lactam ring 2-pyrrolidinone has four carbon atoms and one nitrogen atom. Among the group of derivatives of 2-pyrrolidinones, 1,5-dihydro-2H-pyrrol-2-ones, also known as 3-pyrroline-2-ones, play a significant structural role in a variety of bioactive natural compounds. In this study, three-component reactions were used to successfully synthesize six polysubstituted 3-hydroxy-3-pyrroline-2-one derivatives. The antioxidant activity of the compounds was tested by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, identifying 4-ethoxycarbonyl-3-hydroxy-5-(4-methylphenyl)-1-phenyl-3-pyrroline-2-one (4b) as the most promising radical scavenger. Quantum chemistry calculations of the thermodynamics and kinetics of the radical scavenging activity also suggest that 4b is an effective HO˙ radical scavenger, with k_overall values of 2.05 × 10⁹ and 1.54 × 10¹⁰ M⁻¹ s⁻¹ in pentyl ethanoate and water, respectively. On the other hand, 4b could not scavenge hydroperoxyl radicals in either media. The ability of 4b to scavenge hydroxyl radicals in polar and non-polar environments is comparable to that of conventional antioxidants such as melatonin, gallic acid, indole-3-carbinol, ramalin, or Trolox. Thus 4b may be classed as a promising HO˙ radical scavenger in the physiological environment.

Derivatives of 3-hydroxy-3-pyrroline-2-one were effectively synthesized via multicomponent reactions and exhibited potential HO˙ radical scavenging activity.