Mononuclear nonheme Mn -peroxo complexes are important intermediates in biology, and take part in oxygen activation by photosystem II. Herein, we present work on two isomeric biomimetic side-on Mn -peroxo intermediates with bispidine ligand system and reactivity patterns with aldehydes. The complexes are characterized with UV/Vis and mass spectrometric techniques and reaction rates with cyclohexane carboxaldehyde (CCA) are measured. The reaction gives an unusual regioselectivity switch from aliphatic to aldehyde hydrogen atom abstraction upon deuteration of the substrate, leading to the corresponding carboxylic acid product for the latter, while the former gives a deformylation reaction. Mechanistic details are established from kinetic isotope effect studies and density functional theory calculations. Thus, replacement of C-H by C-D raises the hydrogen atom abstraction barriers and enables a regioselectivity switch to a competitive pathway that is slightly higher in energy.
Download full-text PDF |
Source |
|---|---|
| http://dx.doi.org/10.1002/anie.201905416 | DOI Listing |
Publication Analysis
Top Keywords
Similar Publications
TBAT-Catalyzed Dioxasilinane Formation from Beta-Hydroxy Ketones.
Tetrahedron
February 2025
Department of Chemistry, Western Washington University, Bellingham, WA 98225 (USA).
Beta-hydroxy ketones can be reduced using a sequence of ruthenium-catalyzed silyl etherification followed by tetrabutylammonium fluoride (TBAF) promoted intramolecular hydrosilylation. Switching from TBAF to tetrabutylammonium difluorotriphenylsilicate (TBAT), even without first forming the silyl ether, gave cyclic dioxasilinane products. These somewhat sensitive compounds could be isolated pure by column chromatography using florisil as the stationary phase.
View Article and Find Full Text PDFPhotoinduced Regiodivergent and Enantioselective Cross-Coupling of Glycine Derivatives with Hydrocarbon Feedstocks.
J Am Chem Soc
January 2025
Key Laboratory of Chemical Biology of Fujian Province, iChEM, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, Fujian 361005, China.
Regiodivergent asymmetric synthesis represents a transformative strategy for the efficient generation of structurally diverse chiral products from a single set of starting materials, significantly enriching their enantiomeric composition. However, the design of radical-mediated regiodivergent and enantioselective reactions that can accommodate a wide range of functional groups and substrates has posed significant challenges. The obstacles primarily lie in switching the regioselectivity and achieving high enantiodiscrimination, especially when dealing with high-energy intermediates.
View Article and Find Full Text PDFRegioselectivity switches between anthraquinone precursor fissions involved in bioactive xanthone biosynthesis.
Chem Sci
November 2024
State Key Laboratory Cultivation Base for TCM Quality and Efficacy, School of Pharmacy, Nanjing University of Chinese Medicine Nanjing 210023 China
Xanthone-based polyketides with complex molecular frameworks and potent bioactivities distribute and function in different biological kingdoms, yet their biosynthesis remains under-investigated. In particular, nothing is known regarding how to switch between the C-C (C-selective) and C-C bond (C-selective) cleavages of anthraquinone intermediates involved in biosynthesizing strikingly different frameworks of xanthones and their siblings. Enabled by our characterization of antiosteoporotic brunneoxanthones, a subfamily of polyketides from FB-2, we present herein the brunneoxanthone biosynthetic gene cluster and the C-selective cleavage of anthraquinone (chrysophanol) hydroquinone leading ultimately to the bioactive brunneoxanthones under the catalysis of BruN (an undescribed atypical non-heme iron dioxygenase) in collaboration with BruM as a new oxidoreductase that reduces the anthraquinone into its hydroquinone using NADPH as a cofactor.
View Article and Find Full Text PDFLigand-controlled regiodivergent arylation of aryl(alkyl)alkynes and asymmetric synthesis of axially chiral 9-alkylidene-9,10-dihydroanthracenes.
Nat Commun
October 2024
Inner Mongolia Key Laboratory of Fine Organic Synthesis, Inner Mongolia University, 235 West University Street, Hohhot, 010021, China.
Article Synopsis
- The study demonstrates that the addition of arylboronic acids to aryl(alkyl)alkynes can preferentially form 1,1-diarylalkenes (α-addition) when using a rhodium catalyst with a chiral diene ligand.
- The typical reaction produces carbon-carbon bonds at the alkyl-substituted carbon (β-addition) with a different rhodium/DM-BINAP catalyst, highlighting how ligand choice affects regioselectivity.
- Furthermore, this unique α-addition strategy allows for the efficient synthesis of complex molecules like axially chiral alkylidene dihydroanthracenes with high enantioselectivity via a multi-step process involving migration and cyclization.
An efficient C-glycoside production platform enabled by rationally tuning the chemoselectivity of glycosyltransferases.
Nat Commun
October 2024
Key Laboratory of Chemical Biology and Traditional Chinese Medicine Research (Ministry of Education) and Key Laboratory of Phytochemical R&D of Hunan Province, College of Chemistry and Chemical Engineering, Hunan Normal University, 410081, Changsha, P. R. China.
Despite the broad potential applications of C-glycosides, facile synthetic methods remain scarce. Transforming glycosyltransferases with promiscuous or natural O-specific chemoselectivity to C-glycosyltransferases is challenging. Here, we employ rational directed evolution of the glycosyltransferase MiCGT to generate MiCGT-QDP and MiCGT-ATD mutants which either enhance C-glycosylation or switch to O-glycosylation, respectively.
View Article and Find Full Text PDFWant AI Summaries of new PubMed Abstracts delivered to your In-box?
Enter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!