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1. Synthesis of N -tosylaziridines from substituted alkenes via zirconooxaziridine catalysis

   https://doi.org/10.1039/D2CC00686C  

   Pinarci, Ali A.; Daniecki, Noah; TenHoeve, Tyler M.; Dellosso, Brandon; Madiu, Rufai; Mejia, Liliana; Bektas, Seda E.; Moura-Letts, Gustavo (April 2022, Chemical Communications)

   Herein we report the zirconooxaziridine promoted aziridination of alkenes using chloramine T as the quantitative source of N. The reaction works with high yields, diastereoselectivities and stereospecificity for a wide variety of substituted alkenes. A potential mechanism involving the formation of a zirconooxaziridine complex as the active catalyst has been proposed and initial mechanistic data would indicate that a highly associative mechanism is the predominant pathway for this transformation. 

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2. Synthesis of aminoalcohols from substituted alkenes via tungstenooxaziridine catalysis

   https://doi.org/10.1039/d4ob00022f  

   Madiu, Rufai; Dellosso, Brandon; Doran, Erin L.; Doran, Jenna M.; Pinarci, Ali A.; TenHoeve, Tyler M.; Howard, Amari M.; Stroud, James L.; Rivera, Dominic A.; Moskovitz, Dylan A.; et al (March 2024, Organic & Biomolecular Chemistry)

   Novel tungstenooxaziridine complex promotes the oxyamination of substituted alkenes with high stereoselectivity and stereospecificity. Mechanistic studies provide evidence for a highly selectivesyn-difunctionalization pathway. 

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3. Molecular Determinants of Efficient Cobalt-Substituted Hemoprotein Production in E. coli

   https://doi.org/10.1021/acssynbio.3c00481  

   Weaver, Brian R.; Perkins, Lydia J.; Fernandez Candelaria, Froylan Omar; Burstyn, Judith N.; Buller, Andrew R. (November 2023, ACS Synthetic Biology)

   Exchanging the native iron of heme for other metals yields artificial metalloproteins with new properties for spectroscopic studies and biocatalysis. Recently, we reported a method for the biosynthesis and incorporation of a non-natural metallocofactor, cobalt protoporphyrin IX (CoPPIX), into hemoproteins using the common laboratory strain Escherichia coli BL21(DE3). This discovery inspired us to explore the determinants of metal specificity for metallocofactor biosynthesis in E. coli. Herein, we report detailed kinetic analysis of the ferrochelatase responsible for metal insertion, EcHemH (E. coli ferrochelatase). This enzyme exhibits a small, less than 2-fold preference for Fe2+ over the non-native Co2+ substrate in vitro. To test how mutations impact EcHemH, we used a surrogate metal specificity screen to identify variants with altered metal insertion preferences. This engineering process led to a variant with an ∼30-fold shift in specificity toward Co2+. When assayed in vivo, however, the impact of this mutation is small compared to the effects of alteration of the external metal concentrations. These data suggest that incorporation of cobalt into PPIX is enabled by the native promiscuity of EcHemH coupled with BL21’s impaired ability to maintain transition-metal homeostasis. With this knowledge, we generated a method for CoPPIX production in rich media, which yields cobalt-substituted hemoproteins with >95% cofactor purity and yields comparable to standard expression protocols for the analogous native hemoproteins. 

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4. Roaming in the Unimolecular Decay of syn -Methyl-Substituted Criegee Intermediates

   https://doi.org/10.1021/acs.jpca.3c05859  

   Liu, Tianlin; Lester, Marsha I. (December 2023, The Journal of Physical Chemistry A)
5. Pathways to fluorescence via restriction of intramolecular motion in substituted tetraphenylethylenes

   https://doi.org/10.1039/d1cp04848a  

   Li, Yingchao; Aquino, Adélia J.; Siddique, Farhan; Niehaus, Thomas A.; Lischka, Hans; Nachtigallová, Dana (January 2022, Physical Chemistry Chemical Physics)

   The design of materials with enhanced luminescence properties is a fast-developing field due to the potential applicability of these materials as light-emitting diodes or for bioimaging. A transparent way to enhance the emission properties of interesting molecular candidates is blocking competing and unproductive non-radiative relaxation pathways by the restriction of intramolecular motions. Rationalized functionalization is an important possibility to achieve such restrictions. Using time-dependent density functional theory (TD-DFT) based on the ωB97XD functional and the semiempirical tight-binding method including long-range corrections (TD-LC-DFTB), this work investigates the effect of functionalization of the paradigmatic tetraphenylethylene (TPE) on achieving restricted access to conical intersections (RACI). Photodynamical surface hopping simulations have been performed on a larger set of compounds including TPE and ten functionalized TPE compounds. Functionalization has been achieved by means of electron-withdrawing groups, bulky groups which block the relaxation channels via steric hindrance and groups capable of forming strong hydrogen bonds, which restrict the motion via the formation of hydrogen bond channels. Most of the investigated functionalized TPE candidates show ultrafast deactivation to the ground state due to their still existing structural flexibility, but two examples, one containing –CN and –CF 3 groups and a second characterized by a network of hydrogen bonds, have been identified as interesting candidates for creating efficient luminescence properties in solution. 

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