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.Financial support by Ministerio de Economía, Industria y Competividad (PID2021-122558OB-I00) and Gobierno Vasco (GV-IT1701-22) is gratefully acknowledged. X.d.C. and A.L.-F. thank the Basque Country Government for a predoctoral grant

A Brønsted Acid-Catalyzed Multicomponent Reaction for the Synthesis of Highly Functionalized γ-Lactam Derivatives

Bronsted acids catalyze a multicomponent reaction of benzaldehyde with amines and diethyl acetylenedicarboxylate to afford highly functionalized gamma-lactam derivatives. The reaction consists of a Mannich reaction of an enamine to an imine, both generated in situ, promoted by a phosphoric acid catalyst and a subsequent intramolecular cyclization. The hydrolysis of the cyclic enamine substrate can provide enol derivatives and, moreover, a second attack of the amine on the carboxylate can afford amide derivatives. An optimization of the reaction conditions is presented in order to obtain selectively cyclic enamines that can afford the enol species after selective hydrolysis.Financial support was provided by the Ministerio de Ciencia, Innovacion, y Universidades (RTI2018-101818-B-I00, MCIU/AEI/FEDER, UE), and Gobierno Vasco (GV, IT 992-16) is gratefully acknowledged. X. del Corte thanks Gobierno Vasco for a predoctoral grant

5-Ethoxy-1-(4-methoxyphenyl)-5-methyl-3-phenylimidazolidine-2,4-dione

The title compound is a hydantoin derivative that has been synthesized through a three-component reaction of ethyl pyruvate, p-anisidine and phenyl isocyanate. This paper provides a comprehensive spectral dataset for the title compound, including 1H and 13C{1H} NMR, IR, HRMS, and X-ray crystallography analyses. A tentative mechanism comprising two complementary pathways is provided based on additional experiments with the preformed intermediates.Financial support by Ministerio de Economía, Industria y Competividad (MINECO, CTQ-2015-67871R) and Gobierno Vasco (GV, IT 992-16) is gratefully acknowledged. X.d.C. and A.L.-F. thank the Basque Country Government for a predoctoral grant

Ugi Reaction on α-Phosphorated Ketimines for the Synthesis of Tetrasubstituted α-Aminophosphonates and Their Applications as Antiproliferative Agents

An Ugi three-component reaction using preformed α-phosphorated N-tosyl ketimines with different isocyanides in the presence of a carboxylic acid affords tetrasubstituted α-aminophosphonates. Due to the high steric hindrance, the expected acylated amines undergo a spontaneous elimination of the acyl group. The reaction is applicable to α-aryl ketimines bearing a number of substituents and several isocyanides. In addition, the densely substituted α-aminophosphonate substrates showed in vitro cytotoxicity, inhibiting the growth of carcinoma human tumor cell line A549 (carcinomic human alveolar basal epithelial cell).Financial support by Ministerio de Economía, Industria y Competividad (MINECO, CTQ-2015-67871R) and Gobierno Vasco (GV, IT 992-16) is gratefully acknowledged. X.d.C. and A.L.-F. thank the Basque Country Government for a predoctoral grant

Asymmetric Synthesis of Tetrasubstituted α-Aminophosphonic Acid Derivatives

Due to their structural similarity with natural α-amino acids, α-aminophosphonic acid derivatives are known biologically active molecules. In view of the relevance of tetrasubstituted carbons in nature and medicine and the strong dependence of the biological activity of chiral molecules into their absolute configuration, the synthesis of α-aminophosphonates bearing tetrasubstituted carbons in an asymmetric fashion has grown in interest in the past few decades. In the following lines, the existing literatures for the synthesis of optically active tetrasubstituted α-aminophosphonates are summarized, comprising diastereoselective and enantioselective approaches.Financial support by Ministerio de Economía, Industria y Competividad (MINECO, CTQ-2015-67871R) and Gobierno Vasco (GV, IT 992-16) is gratefully acknowledged. X.d.C. and A.L.-F. thank the Basque Country Government for a predoctoral grant

Chiral self-recognition in a bispericyclic cyclodimerisation reaction of 1-azadienes

Hermaphroditism of molecules: as in nature some species behave as male or female depending on the environment, herein we report a bispericyclic dimerisation of cyclic 1-azadienes where a molecule can behave as either diene or dienophile, depending on its location at the transition state. In a symmetrical reactive complex, here represented by an arbitrary reference system, a molecule that is positioned on top acts as the diene unit, while the dienophile partner is the one situated at the bottom. In addition, a strong chiral self-recognition phenomenon is observed, where each enantiomer within a racemic mixture of chiral 1-azadienes exclusively recognises itself. In order to shed some light into the understanding of the chiral self-recognition effect, an extensive DFT study of the reaction pathway is provided, concluding that a combination of attractive π-stacking forces and repulsive steric interactions is at the origin of the high stereospecificity of the reaction.Financial support by Ministerio de Ciencia, Innovación y Universidades (MCIU-Madrid) (PID2021-122558OB-I00, UE), and Eusko Jaurlaritza (GV, IT1701-22 and IT-1553-22; UPV-EHU) is gratefully acknowledged. The authors are grateful for technical and human support provided by SGIker (UPV/EHU/ERDF, EU). The authors thank SGI/IZO-SGIker of the UPV/EHU and the DIPC for the generous allocation of analytical and computational resources. A. L.-F. thanks the Basque Country Government for a predoctoral grant

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

[EN] 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.Financial support by Ministerio de Economía, Industria y Competividad (RTI2018-101818- B-I00) and Gobierno Vasco (GV, IT 992-16) is gratefully acknowledged. X.d.C. and A.L.-F. thank the Basque Country Government for a predoctoral grant

Exploring the Surface of the Ectodomain of the PD-L1 Immune Checkpoint with Small-Molecule Fragments

Development of small molecules targeting the PD-L1/PD-1 interface is advancing both in industry and academia, but only a few have reached early-stage clinical trials. Here, we take a closer look at the general druggability of PD-L1 using in silico hot spot mapping and nuclear magnetic resonance (NMR)-based characterization. We found that the conformational elasticity of the PD-L1 surface strongly influences the formation of hot spots. We deconstructed several generations of known inhibitors into fragments and examined their binding properties using differential scanning fluorimetry (DSF) and protein-based nuclear magnetic resonance (NMR). These biophysical analyses showed that not all fragments bind to the PD-L1 ectodomain despite having the biphenyl scaffold. Although most of the binding fragments induced PD-L1 oligomerization, two compounds, TAH35 and TAH36, retain the monomeric state of proteins upon binding. Additionally, the presence of the entire ectodomain did not affect the binding of the hit compounds and dimerization of PD-L1. The data demonstrated here provide important information on the PD-L1 druggability and the structure-activity relationship of the biphenyl core moiety and therefore may aid in the design of novel inhibitors and focused fragment libraries for PD-L1.This research has been supported by Grants Maestro 2017/26/A/ST5/00572 (to T.A.H.) , Sonata UMO-2020/39/D/ST4/01344 (to E.S.) , Preludium UMO-2021/41/N/ST4/03485 (to M.Z.) , and Preludium UMO-2020/37/N/ST4/02691 (to D.M.) from the National Science Centre, Poland. X.d.C. thanks the Basque Country Government for the predoctoral and EGONLABUR grants

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.Financial support by Ministerio de Economía, Industria y Competividad (MINECO) (RTI2018-101818-B-I00) and Gobierno Vasco (GV, IT 992-16) is gratefully acknowledged. The authors thank SGIker (UPV/EHU/ERDF, EU) for the technical and human support provided. X.d.C. and A.L.-F. thank the Basque Country Government for a predoctoral grant. I.V.-B. thanks the University of the Basque Country (UPV/EHU) for the granted postdoctoral fellowship (ESPDOC19/47). M.S.-R. thanks the University of the Basque Country (UPV/EHU) for the granted pre-doctoral fellowship (PIF17/79)

Nutlin-3a-aa: Improving the Bioactivity of a p53/MDM2 Interaction Inhibitor by Introducing a Solvent-Exposed Methylene Group

Nutlin-3a is a reversible inhibitor of the p53/MDM2 interaction. We have synthesized the derivative Nutlin-3a-aa bearing an additional exocyclic methylene group in the piperazinone moiety. Nutlin-3a-aa is more active than Nutlin-3a against purified wild-type MDM2, and is more effective at increasing p53 levels and releasing transcription of p53 target genes from MDM2-induced repression. X-ray analysis of wild-type MDM2-bound Nutlin-3a-aa indicated that the orientation of its modified piperazinone ring was altered in comparison to the piperazinone ring of MDM2-bound Nutlin-3a, with the exocyclic methylene group of Nutlin-3a-aa pointing away from the protein surface. Our data point to the introduction of exocyclic methylene groups as a useful approach by which to tailor the conformation of bioactive molecules for improved biological activity.This work was generously supported by the Deutsche Forschungsgemeinschaft (BE 4572/3-1 to T.B.). We extend our thanks to Barbara Klüver, Katrin Eckhardt, Nadiya Brovchenko, and Domenique Herbstritt for experimental support. Parts of the data described in this manuscript have been published in the dissertation of Florian Nietzold (Leipzig University, 2019).31 In addition, this work was financially supported by the National Science Centre, Poland (NCN) under Grant Symphony 2014/12/W/NZ1/00457 (to T.A.H). We thank HZB for the allocation of synchrotron radiation beamtime. We acknowledge the MCB Structural Biology Core Facility (supported by the TEAM TECH CORE FACILITY/2017-4/6 grant from the Foundation for Polish Science) for valuable support. Open Access funding enabled and organized by Projekt DEAL