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OPEN Repository

Welcome to OPEN - the Repository of Open Scientific Publications, run by the Interdisciplinary Centre for Mathematical and Computational Modelling, University of Warsaw, previously operating as the CeON Repository. The Repository enables Polish researchers from all fields to openly share their articles, books, conference materials, reports, doctoral theses, and other scientific texts.

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22936 archived items

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Item

Aqueous Micellar Environment Impacts the Co-Catalyzed Phototransformation: A Case Study

(American Chemical Society, 2024) Wincenciuk, Aleksandra; Cmoch, Piotr; Giedyk, Maciej; Andersson, Martin P.; Gryko, Dorota; Institute of Organic Chemistry, Polish Academy of Sciences; Center for Integrative Petroleum Research, King Fahd University of Petroleum and Minerals, Kingdom of Saudi Arabia

In recent years, methodologies that rely on water as the reaction medium have gained considerable attention. The unique properties of micellar solutions were shown to improve the regio-, stereo-, and chemoselectivity of different transformations. Herein, we demonstrate that the aqueous environment is a suitable medium for a visible light driven cobalt-catalyzed reaction involving radical species. In this system, reduced vitamin B12 reacts with alkyl halides, generating radicals that are trapped by the lipophilic olefin present in the Stern layer. A series of NMR measurements and theoretical studies revealed the location of reaction components in the micellar system.

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Cascade Transformation of the Ansamycin Benzoquinone Core into Benzoxazole Influencing Anticancer Activity and Selectivity

(American Chemical Society, 2023) Skrzypczak, Natalia; Pyta, Krystian; Bohusz, Wiktor; Leśniewska, Aleksandra; Gdaniec, Maria; Ruszkowski, Piotr; Schilf, Wojciech; Bartl, Franz; Przybylski, Piotr; Faculty of Chemistry, Adam Mickiewicz University, Poznań; Department of Pharmacology, Poznań University of Medical Sciences; Institute of Organic Chemistry, Polish Academy of Sciences; Lebenswissenschaftliche Fakultӓt, Institut fȕr Biologie, Biophysikalische Chemie Humboldt - Universitӓt zu Berlin

The metal-free cascade transformation of geldanamycin benzoquinone core is proposed at relatively mild conditions. This approach yields new benzoxazole ansamycin antibiotics and enables their functionalization in an atom-economic manner, irrespective of the type of amine used. The analysis of the heterocyclization course reveals the dependence of its rate on the nature of the para-substituent within the benzylamine moiety (EDG/EWG) and the strength of the base. The reduction of the ansamycin core enables an increase in anticancer potency and selectivity.

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Carboxylated Pillar[6]arene Emulates Pillar[5]arene in the Host–Guest Crystal Complexes and Shows Conformational Flexibility in the Solution/Gas Phase

(American Chemical Society, 2023) Butkiewicz, Helena; Kosiorek, Sandra; Sashuk, Volodymyr; Zimnicka, Magdalena M.; Danylyuk, Oksana; Institute of Physical Chemistry, Polish Academy of Sciences; Institute of Organic Chemistry, Polish Academy of Sciences

Despite the thriving interest in the aqueous complexation properties of carboxylated pillar[6]arene, its solid state supramolecular chemistry has remained a mystery. Here, overcoming challenging crystallogenesis, we report the first crystallographic authentication of carboxylated pillar[6]arene in the form of two host–guest inclusion complexes with methyl viologen and pentamidine. The key to the successful crystallization of carboxylated pillar[6]arene is the mixed ionization state of its 12 carboxylic substituents. The deprotonation of several but not all substituents enables intermolecular hydrogen bonding and, as a result, “gluing” and crystallization of pillar[6]arene complexes with the aid of carboxylic-carboxylate, carboxylic-carboxylic, and amidinium-carboxylate supramolecular synthons. Single crystal X-ray diffraction analysis revealed that upon guest inclusion pillar[6]arene adopts a quasi-pentagonal shape rather than the expected hexagonal shape. The squeezed quasi-pentagonal conformation of the six-membered macrocycle is stabilized by two intramolecular hydrogen bonds between pillar[6]arene substituents. Moreover, the distinctive deviation of the macrocycle from hexagonal shape stays operative in the solution/gas phase as concluded from ion mobility mass spectrometry (IM-MS) studies and theoretical calculations. These results provide the first insight into how to gain control over the conformation of flexible pillar[6]arene with a view of solid state design of more advanced supramolecular host–guest structures.

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Carboxylated Pillar[5]arene Meets Medicinal Biguanides: Host–Guest Complexes with Alexidine and Phenformin in the Crystal and Solution/Gas Phase

Here, we discuss crystal and solution/gas-phase complexes of carboxylated pillar[5]arene with two cationic guests, alexidine and phenformin, revealing host–guest and assembly curiosities, the role of hydrogen bonding, and cavity inclusion versus exo-mode binding. We show that the combination of carboxylated pillar[5]arene with bis(biguanidinium) guest alexidine results in the crystallization of open-type supramolecular architecture. This is also the first crystal structure of alexidine ever reported. The crystallization of pillar[5]arene with biguanidinium drug phenformin affects a rare solid-state complex comprising two cavity inclusion modes within the same crystal lattice. The winner in the competition between ethanol molecules and an organic cation (phenformin) for access to the cavity of pillar[5]arene is undecided, visualized as a “snapshot” of these two inclusion possibilities in one crystal structure. Our results demonstrate that carboxylated pillar[n]arenes can be a useful addition to the macrocyclic toolkit for the facilitation of the crystallization of bio(macro)molecules. Moreover, the IM-MS analysis of the precrystallization solutions of pillar[5]arene host and biguanide guests has shown the presence of structures and conformations closely related to those observed in the crystal forms. The most intriguing results obtained for a pillar[5]arene–alexidine complex imply a conformational evolution of the complex over 24 h. The IM-MS analysis complemented by theoretical calculations may be applied to predict and examine the crystallization process of host–guest systems, complementing crystallographic studies.

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Aryl versus Alkyl Redox-Active Diazoacetates ─ Light-Induced C–H Insertion or 1,2-Rearrangement

(American Chemical Society, 2023) Santiago, João V.; Orłowska, Katarzyna; Ociepa, Michał; Gryko, Dorota; Institute of Organic Chemistry, Polish Academy of Sciences

Diazo compounds with redox-active leaving groups are versatile reagents for orthogonal functionalizations, previously utilized in the Rh-catalyzed synthesis of highly substituted cyclopropanes. Photochemical activation of aryl-substituted diazoacetates generates carbenes, whereas redox-active esters can furnish C-radicals via the photoexcitation of EDA complexes. However, the photochemical behavior of these two functionalities, while present in one molecule, remains to be defined. We demonstrate that under light irradiation, reactions occur only on the diazomoiety, leaving the NHPI functionality intact. Not only aryl- but also alkyl-substituted NHPI diazoacetates are activated by blue light; either C−H insertion or the hydrogen/carbon 1,2-rearrangement occurs depending on the aryl/alkyl group.

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