A JOURNEY IN THE ORGANOCATALYSED AND MULTICOMPONENT SYNTHESIS OF 3,3-DISUBSTITUTED AND SPIRO-OXINDOLES

2-Oxindoles, especially those 3,3-disubstituted or spiro-fused to other cyclic frameworks, continue to be recognized as valuable compounds for drug discovery. They are present in a large number of natural and unnatural compounds with important biological activities and serve as key intermediates for the synthesis of many kinds of drug candidates.1 In particular, spirooxindoles, having cyclic structures fused at the C3 carbon, move away from the flat heterocycles encountered in many drug discovery programs. For this reason, they are of special interest, being able to potentially provide improved physicochemical properties in their interaction with biological systems.2 As more examples of the enantiospecific biological activity are identified, efficient and reliable asymmetric synthesis of such compounds becomes more and more valuable. In this context, the identification of asymmetric methods that achieve high stereoselectivity in the synthesis of heterocyclic compounds, in particular bearing tetrasubstituted or spiro-stereocenters, remains challenging. In this context, my research was aimed to the synthesis of oxindole-based libraries, exploiting protocols at the cutting edge of synthetic chemistry, such as MCRs and organocatalysis. Considering the great attention around optically active \u3b4-amino-\u3b1,\u3b2-unsaturated carbonyl compounds as important building blocks in the synthesis of biologically active compounds,3 for my first project I focused my attention on the synthesis of 3-amino-3-(5-oxo-2,5-dihydrofuran-2-yl)indolin-2-ones derivatives via a BINOL-based phosphoric acids organocatalyzed vinylogous Mannich-type reaction.4 The desired products were obtained in general good yields and high enantiomeric excesses considering the challenge in the formation of a quaternary stereocenter consecutive with a bulky tertiary one. The stereochemistry of the final products was assigned by chemical correlation with respect to a reported compound5 and the stereochemical outcome was also rationalized by computational study. Moreover, I studied the Biginelli reaction, a three component cyclocondensation between alkyl acetoacetates, urea and a carbonyl compound, as a practical method for the synthesis of biologically important 3,4-dihydropyrimidine-2(1H)-ones.6 In particular, BINOL-phosphoric acids have been used in the development of the first enantioselective organocatalyzed multicomponent Biginelli-like reaction applied to a ketone, allowing to obtain a small library of spiro[indoline-pyrimidine]-dione derivatives in good yields and enantioselectivity.7 During the second year, I focused my attention on the synthesis of 2-oxindoles spiro-fused with four- and five-membered rings. Considering the recent medicinal chemists' interest in oxindole-based thiazolidine compounds as antitumor agents for the inhibition of the p53-MDM2 PPI,8 a novel synthetic approach towards spirooxindole-fused thiazolidines has been developed, based on two sequential multicomponent reactions (MCRs), namely the Asinger and two different Ugi-type reactions, Joulli\ue9-Ugi 3-CR and azido-Ugi 3-CR.9,10 The traditional Asinger 4-MCR11 allows to synthesize the thiazoline scaffold by treating a ketone with sulfur and ammonia with high atom economy. However, considerable more flexible is the \u201cresynthesis protocol\u201d in which an \u3b1-sulfanyl-carbonyl compound is directly used.12 The first part of the project involved the development of an Asinger-type reaction using isatin as the oxo component. After a screening of reaction conditions, the best parameters were selected to perform the substrate scope synthesizing different spirooxindole-fused 3-thiazolines in good yields.13 Spirooxindole-fused 3-thiazolines bearing an hydrogen as substituent on the double bond proved to be useful for the application of sequential MCRs. By application of Joulli\ue8-Ugi and azido-Ugi reactions respectively, two small families of spiro-[indoline-3,2\u2019-thiazolidine] derivatives were obtained in good yields and high diasteroselectivity.14 Another project developed during the second year was focused on the azetidine moiety. This strained four-membered ring system occurs as a structural motif in several natural products and pharmaceutical agents.15 Despite the interest in azetidin-2-ones, azetidines have received much less attention compared to their lower and higher homologues.16 Considering my interest in the synthesis of spirooxindoles derivatives, combined with the growing interest in hybrid drugs as therapeutic agents, I planned to connect the two pharmacologically relevant moieties, oxindole and azetidine, in a spiro arrangement. To do this, the formal [2+2] annulation reaction17 of isatins with allenoates has been considered as a practical and direct strategy to obtain highly functionalized chiral spirooxindole-based 4-methyleneazetidines with a high level of atom-economy.18 After a screening of reaction conditions, the best parameters were selected to extend the substrate scope obtaining different spirooxindole-fused 4-methyleneazetidines in good yield and excellent diasteroselectivity. Considering the increasing interest for the development of catalytic asymmetric synthesis, I spent the third year in the development of a more efficient asymmetric cinchona-based organocatalyzed approach for the synthesis of enantiomerically enriched spirooxindole-fused 4-methyleneazetidines. After a deep screening of catalysts and reaction conditions, best parameters were applied to the reaction scope obtaining spirooxindole-fused 4-methyleneazetidines in good yields and enatiomeric ratios.19 In conclusion, during my PhD, I synthesized six different 3,3-disubstituted and spirooxindole-based scaffolds using innovative approaches. In some cases, novel asymmetric organocatalyzed methodologies have been developed leading to enantiomerically enriched products. In other cases, more relevance was given to the multicomponent synthetic strategy for the rapid construction of highly functionalized scaffolds for drug discovery programs. Indeed, some of these compounds are under biological evaluation in collaborations with Merck (Pharma). References: 1. Singh G. et al. Chem. Rev. 2012, 112, 6104. 2. Yang C. et al. Org. Biomol. Chem. 2015, 13, 4869. 3. Ruan S.T. et al. Org. Lett. 2011, 13, 4938. 4. Rainoldi G. et al. Org. Biomol. Chem. 2016, 14, 7768. 5. Rao V. U. B. et al. Org. Lett., 2014, 16, 648. 6. Goss J. et al. J. Org. Chem. 2008, 73, 7651. 7. Stucchi M. et al. J. Org. Chem. 2016, 81, 1877. 8. Bertamino A. et al. J. Med. Chem. 2013, 56, 5407. 9. Katsuyama A. et al. Org. Lett. 2016, 18, 2552; 10. Nenajdenko G. et al. Eur. J. Org. Chem. 2013, 6379. 11. Asinger F. Angew. Chem. 1956, 68, 377. 12. Keim, W. and Offermanns, H. Angew. Chem. Int. Ed. 2007, 46, 6010. 13. Rainoldi G. et al. Synlett 2016, 27, 2831. 14. Rainoldi G. et al. ACS Comb. Sci. 2017, Just Accepted. 15. Brandi A. et al. Chem. Rev. 2008, 108, 3988. 16. Orr S. T. M. et al. ACS Med. Chem. Lett. 2015, 6, 156. 17. Shi M. et al. J. Org. Chem. 2005. 8. Rainoldi G. et al. Chem. Commun. 2016, 52, 11575. 19. Rainoldi G. et al. Molecules 2017, 22, 2016

Highly diastereoselective entry into chiral spirooxindole-based 4-methyleneazetidines via formal [2+2] annulation reaction

We describe here a diastereoselective, DABCO-catalyzed reaction of allenoates with chiral N-tert-butanesulfinyl ketimines derived from isatin

Organocatalytic access to enantioenriched spirooxindole-based 4-methyleneazetidines

This work describes the synthesis of enantioenriched spiro compounds, incorporating the azetidine and the oxindole motifs. The preparation relies on a formal [2 + 2] annulation reaction of isatin-derived N-tert-butylsulfonyl ketimines with allenoates. The asymmetric induction is secured by an organocatalytic strategy, exploiting a bifunctional cinchona-type \uce\ub2-isocupridine-based catalyst. Some post-transformation products, including unexpected spiropyrroline and 3,3-disubstituted oxindole derivatives, are also presented

Strength asymmetries are muscle-specific and metric-dependent

We investigated if dominance affected upper limbs muscle function, and we calculated the level of agreement in asymmetry direction across various muscle-function metrics of two heterologous muscle groups. We recorded elbow flexors and extensors isometric strength of the dominant and non-dominant limb of 55 healthy adults. Participants performed a series of explosive contractions of maximal and submaximal amplitudes to record three metrics of muscle performance: maximal voluntary force (MVF), rate of force development (RFDpeak), and RFD-Scaling Factor (RFD-SF). At the population level, the MVF was the only muscle function that showed a difference between the dominant and non-dominant sides, being on average slightly (3-6%) higher on the non-dominant side. At the individual level, the direction agreement among heterologous muscles was poor for all metrics (Kappa values ≤ 0.15). When considering the homologous muscles, the direction agreement was moderate between MVF and RFDpeak (Kappa = 0.37) and low between MVF and RFD-SF (Kappa = 0.01). The asymmetries are muscle-specific and rarely favour the same side across different muscle-performance metrics. At the individual level, no one side is more performative than the other: each limb is favoured depending on muscle group and performance metric. The present findings can be used by practitioners that want to decrease the asymmetry levels as they should prescribe specific exercise training for each muscle

he Cut-Off Value for Classifying Active Italian Children Using the Corresponding National Version of the Physical Activity Questionnaire

The present study aimed to determine a cut-off value following the filling in of a questionnaire (PAQ-C-It) to identify active Italian children. One-hundred-twenty-nine primary school children (5 Piedmont schools; 47.3% female; mean age = 10 ± 1 years) wore an accelerometer (Actigraph wGT3X-BT) to objectively quantify individual moderate-to-vigorous physical activity during one week. Afterwards, the PAQ-C-It was filled in by participants. A ROC curve procedure was applied to obtain an active/non-active cut-off point. Spearman's correlation coefficient was also applied to establish the relationship between the two parameters. According to the ROC analysis, the PAQ-C-It cut-off point value is identifiable at >2.75 to indicate active children (area under the curve = 0.62; standard error = 0.05; p = 0.025; coefficient intervals = 0.518-0.716; sensitivity = 0.592, specificity = 0.382), determining that 65 participants (55%) were non-active (mean PAQ-C-It value = 2.3 ± 0.4; active mean PAQ-C-It value = 3.3 ± 0.4). Spearman's correlation coefficient results were significant but with a small effect size (rho = 0.214; p = 0.008). In conclusion, the present results suggest that the PAQ-C-It can be cautiously used as tool to practically classify active Italian children because of a non-solid relationship between respective accelerometer data and MVPA daily data

Screening, diagnosis and monitoring of sarcopenia:When to use which tool?

Background & aims: Sarcopenia is a muscle disorder associated with loss of muscle mass, strength and function. Early screening, diagnosis and treatment may improve outcome in different disease conditions. A wide variety of tools for estimation of muscle mass is available and each tool has specific technical requirements. However, different investigational settings and lack of homogeneity of populations influence the definition of gold standards, proving it difficult to systematically adopt these tools. Recently, the European Working Group on Sarcopenia in Older People (EWGSOP) published a revised recommendation (EWGSOP-2) and algorithm for using tools for screening and diagnosing sarcopenia. However, agreement of the EWGSOP2 criteria with other classifications is poor and although an overview of available tools is valuable, for the purpose of clinical decision-making the reverse is useful; a given scenario asks for the most suitable tools. Results: Tools were identified for screening, diagnostics and longitudinal monitoring of muscle mass. For each of these clinical scenarios the most appropriate tools were listed and for each technique their usability is specified based on sensitivity and specificity. Based on this information a specific recommendation is made for each clinical scenario. Conclusion: This narrative review provides an overview of currently available tools and future developments for different clinical scenarios such as screening, diagnosis and longitudinal monitoring of alterations in muscle status. It supports clinical decision-making in choosing the right tools for muscle mass quantification depending on the need within a given clinical scenario as well as the local availability and expertise. (C) 2022 The Author(s). Published by Elsevier Ltd on behalf of European Society for Clinical Nutrition and Metabolism