Brönsted Acid Catalyzed Multicomponent Synthesis of Phosphorus and Fluorine-Derived γ-Lactam Derivatives

Organocatalytic cyclization-rearrangement cascade reaction: asymmetric construction of γ-lactams

We report a chiral thiourea-catalyzed Michael/ring-reorganization cyclization of 3-methyleneoxindoles with N-(p-toluenesulfonyl)-α-amino ketones, facilitating the asymmetric synthesis of γ-lactams. This method efficiently generates a range of optically pure γ-lactams, in yields ranging from 60% to 86% and excellent stereoselectivity (up to 20 : 1 dr, >99% ee). The gram-scale experiments confirmed the scalability of the reaction without compromising the yield or stereoselectivity. Performed under mild conditions, this investigation showcases its potential applicability for synthesizing complex chiral γ-lactams with consecutive three chiral centers.

Exploring the Reactivity of Rigid 1-Azadienes Derived from Methylene γ-Lactams. Applications to the Stereoselective Synthesis of Spiro-γ-Lactams

A study on the reactivity of rigid 1-azadienes derived from methylene γ-lactams is reported. Through the functionalization of 1-amino α,β-unsaturated γ-lactam derivatives, easily available from a multicomponent reaction of amines, aldehydes, and pyruvates, it is possible to in situ generate rigid 1-azadienes locked by a γ-lactam core. The 4π-electron system of those rigid 1-azadienes can behave as both diene and dienophile species through a spontaneous cyclodimerization reaction or exclusively as dienes or dienophiles if they are trapped with imines or cyclopentadiene, respectively. The use of chiral rigid 1-azadienes as dienophiles in the cycloaddition reaction with cyclopentadiene leads to the formation of spiro-γ-lactams bearing four stereogenic centers in a highly stereospecific manner, reporting the first example of the use of methylene-γ-lactams in the synthesis of spirocycles.

Diethyl(benzamido(diisopropoxyphosphoryl)methyl) phosphonate

Bisphosphonates are widely used in medicine and related areas, mainly for the treatment of bone diseases, such as osteoporosis. However, their synthesis is usually performed under harsh reaction conditions. In order to overcome this limitation, the present work illustrates a new synthetic route to access the title α-aminobisphosphonate in milder reaction conditions using α-phosphorylated imines as key intermediates.

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.

Amination of 5-Spiro-Substituted 3-Hydroxy-1,5-dihydro-2H-pyrrol-2-ones

The 3-hydroxy-1,5-dihydro-2H-pyrrol-2-one motif is a valuable scaffold in drug discovery. The replacement of the 3-oxy fragment in 3-hydroxy-1,5-dihydro-2H-pyrrol-2-ones-based compounds with a 3-amino one (3-amino analogs of 3-hydroxy-1,5-dihydro-2H-pyrrol-2-ones, 3-amino-1,5-dihydro-2H-pyrrol-2-ones) can play a crucial role in their biological effect. Thus, approaches to 3-amino-1,5-dihydro-2H-pyrrol-2-ones are of significant interest. We developed an approach to 5-spiro-substituted 3-amino-1,5-dihydro-2H-pyrrol-2-ones that could not be obtained using previously reported approaches (reactions of 3-hydroxy-1,5-dihydro-2H-pyrrol-2-ones with amines). The developed approach is based on the thermal decomposition of 1,3-disubstituted urea derivatives of 5-spiro-substituted 3-hydroxy-1,5-dihydro-2H-pyrrol-2-ones, which were prepared via their reaction with carbodiimides.

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

An efficient synthetic methodology for the preparation of 3-amino 1,5-dihydro-2H-pyrrol-2-ones through a multicomponent reaction of amines, aldehydes, and pyruvate derivatives is reported. In addition, the densely substituted lactam substrates show in vitro cytotoxicity, inhibiting the growth of carcinoma human tumor cell lines HEK293 (human embryonic kidney), MCF7 (human breast adenocarcinoma), HTB81 (human prostate carcinoma), HeLa (human epithelioid cervix carcinoma), RKO (human colon epithelial carcinoma), SKOV3 (human ovarian carcinoma), and A549 (carcinomic human alveolar basal epithelial cell). Given the possibilities in the diversity of the substituents that offer the multicomponent synthetic methodology, an extensive structure-activity profile is presented. In addition, both enantiomers of phosphonate-derived γ-lactam have been synthesized and isolated and a study of the cytotoxic activity of the racemic substrate vs. its two enantiomers is also presented. 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.

Photocatalytic Cyclization/Defluorination Domino Sequence to Access 3-Fluoro-1,5-dihydro-2H-pyrrol-2-one Scaffold

We herein report an unprecedented photoinduced cyclization/defluorination domino process of N-allylbromodifluoroacetamide with cyclic secondary amines. Consequently, a wide array of valuable 3-fluoro-1,5-dihydro-2H-pyrrol-2-ones were facilely prepared from readily available starting materials under mild conditions. Preliminary mechanistic investigations suggest that a radical chain propagation and amine-promoted defluorination pathway are presumably involved in this transformation.