Grosskopf, Johannes and Plaza, Manuel and Kutta, Roger Jan and Nuernberger, Patrick and Bach, Thorsten (2023) Creating a Defined Chirality in Amino Acids and Cyclic Dipeptides by Photochemical Deracemization. ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, 62 (47): e202313606. ISSN 1433-7851, 1521-3773
Full text not available from this repository. (Request a copy)Abstract
2,5-Diketopiperazines are cyclic dipeptides displaying a wide range of applications. Their enantioselective preparation has now been found possible from the respective racemates by a photochemical deracemization (53 examples, 74 % to quantitative yield, 71-99 % ee). A chiral benzophenone catalyst in concert with irradiation at lambda=366 nm enables to establish the configuration at the stereogenic carbon atom C6 at will. If other stereogenic centers are present in the diketopiperazines they remain unaffected and a stereochemical editing is possible at a single position. Consecutive reactions, including the conversion into N-aryl or N-alkyl amino acids or the reduction to piperazines, occur without compromising the newly created stereogenic center. Transient absorption spectroscopy revealed that the benzophenone catalyst processes one enantiomer of the 2,5-diketopiperazines preferentially and enables a reversible hydrogen atom transfer that is responsible for the deracemization process. The remarkably long lifetime of the protonated ketyl radical implies a yet unprecedented mode of action.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | BENZOPHENONE; 2,5-DIKETOPIPERAZINES; MECHANISM; Amino Acids; C-H Activation; Enantioselectivity; Nitrogen Heterocycles; Photochemistry |
| Subjects: | 500 Science > 540 Chemistry & allied sciences |
| Divisions: | Chemistry and Pharmacy > Institut für Physikalische und Theoretische Chemie > Chair of Physical Chemistry I > Prof. Dr. Patrick Nürnberger |
| Depositing User: | Dr. Gernot Deinzer |
| Date Deposited: | 16 Mar 2024 15:34 |
| Last Modified: | 16 Mar 2024 15:34 |
| URI: | https://pred.uni-regensburg.de/id/eprint/60278 |
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