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This is the peer reviewed version of the following article: Rigotti, T., Asenjo‐Pascual, J., Martín‐Somer, A., Milán Rois, P., Cordani, M., Díaz‐Tendero, S., . & Alemán. Boron Dipyrromethene (BODIPY) as Electron‐Withdrawing Group in Asymmetric Copper‐Catalyzed [3+ 2] Cycloadditions for the Synthesis of Pyrrolidine‐Based Biological Sensors. Advanced Synthesis & Catalysis Volume 362, Issue 6, 17 March 2020, Pages 1345-1355 , which has been published in final form at https://doi.org/10.1002/adsc.201901465. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions ; In this work, we describe the use of Boron Dipyrromethene (BODIPY) as electron-withdrawing group for activation of double bonds in asymmetric copper-catalyzed [3+2] cycloaddition reactions with azomethine ylides. The reactions take place under smooth conditions and with high enantiomeric excess for a large number of different substituents, pointing out the high activation of the alkene by using a boron dipyrromethene as electron-withdrawing group. Experimental, theoretical studies and comparison with other common electron-withdrawing groups in asymmetric copper-catalyzed [3+2] cycloadditions show the reasons of the different reactivity of the boron dipyrromethene derivatives, which can be exploited as a useful activating group in asymmetric catalysis. Additional experiments show that the so obtained pyrrolidines can be employed as biocompatible biosensors, which can be located in the endosomal compartments and do not present toxicity in three cell lines ; This work was supported by the Spanish Government (RTI2018‐095038‐B‐I00, CTQ2016‐76061‐P, SAF2017‐87305‐R), Comunidad de Madrid (IND2017/IND‐7809), and co‐financed by European Structural and Investment Fund. We acknowledge the generous allocation of computing time at the CCC (UAM). Financial support from the Spanish Ministry of Economy and Competitiveness, through the ''Maria de Maeztu'' Program of Excellence in R&D (MDM‐2014‐0377), is also acknowledged. Asociación Española Contra el Cáncer, and IMDEA Nanociencia acknowledge support from the ′Severo Ochoa′ Programme for Centres of Excellence in R&D (MINECO, Grant SEV‐2016‐0686). P.M.R thanks the Ministry of Economy, Industry and competitiveness of Spain for the FPI grant (BES‐2017.082521). A.M.S. thanks CAM for a postdoctoral contract (2016‐T2/IND‐1660)

The COVID-19 pandemic has brought to light the need for fast and sensitive detection methods to prevent the spread of pathogens. The scientific community is making a great effort to design new molecular detection methods suitable for fast point-of-care applications. In this regard, a variety of approaches have been developed or optimized, including isothermal amplification of viral nucleic acids, CRISPR-mediated target recognition, and read-out systems based on nanomaterials. Herein, we present CASCADE (CRISPR/CAS-based Colorimetric nucleic Acid DEtection), a sensing system for fast and specific naked-eye detection of SARS-CoV-2 RNA. In this approach, viral RNA is recognized by the LwaCas13a CRISPR protein, which activates its collateral RNase activity. Upon target recognition, Cas13a cleaves ssRNA oligonucleotides conjugated to gold nanoparticles (AuNPs), thus inducing their colloidal aggregation, which can be easily visualized. After an exhaustive optimization of functionalized AuNPs, CASCADE can detect picomolar concentrations of SARS-CoV-2 RNA. This sensitivity is further increased to low femtomolar (3 fM) and even attomolar (40 aM) ranges when CASCADE is coupled to RPA or NASBA isothermal nucleic acid amplification, respectively. We finally demonstrate that CASCADE succeeds in detecting SARS-CoV-2 in clinical samples from nasopharyngeal swabs. In conclusion, CASCADE is a fast and versatile RNA biosensor that can be coupled to different isothermal nucleic acid amplification methods for naked-eye diagnosis of infectious diseases. ; This work was supported by the Spanish Ministry of Economy and Competitiveness (SAF2017-87305-R, PID2020-119352RB-I00), Instituto de Salud Carlos III (FONDO-COVID19:COV20/00144 and COV20/00122) and Madrid Regional Government (NANOCOV-CM and IND2017/IND7809). C.E-N, M. L-V and C.R-D thank Madrid Regional Government for the pre-doctoral Grants (PEJD-2017-PRE/BMD-3730, PEJD-2018-PRE/IND-9584 and PEJD-2017-PRE/IND-4438). P.M.R thanks the Ministry of Economy, Industry and ...