Journal article

Publication year: 2020

Pages: 1835-1846

Journal: The Journal of Organic Chemistry

Volume number: 85

Issue number: 4

ISSN: 0022-3263

DOI Link: https://doi.org/10.1021/acs.joc.9b01913

Publisher: American Chemical Society

Abstract: 
We present a novel concept for the in situ control of site-selectivity of catalytic acetylations of partially protected sugars using light as external stimulus and oligopeptide catalysts equipped with an azobenzene moiety. The isomerizable azobenzene-peptide backbone defines the size and shape of the catalytic pocket, while the pi-methyl-L-histidine (Pmh) moiety transfers the electrophile. Photoisomerization of the E- to the Z-azobenzene catalyst (monitored via NMR) with an LED (lambda = 365 nm) drastically changes the chemical environment around the catalytically active Pmh moiety, so that the light-induced change in the catalyst shape alters site-selectivity. As a proof of principle, we employed (4,6-O-benzylidene)methyl-alpha-D-pyranosides, which provide a change in regioselectivity from 2:1 (E) to 1:5 (Z) for the monoacetylated products at room temperature. The validity of this new catalyst-design concept is further demonstrated with the regioselective acetylation of the natural product quercetin. In situ irradiation NMR spectroscopy was used to quantify photostationary states under continuous irradiation with UV light.

Harvard Citation style: Niedek, D., Erb, F., Topp, C., Seitz, A., Wende, R., Eckhardt, A., et al. (2020) In Situ Switching of Site-Selectivity with Light in the Acetylation of Sugars with Azopeptide Catalysts, The Journal of Organic Chemistry, 85(4), pp. 1835-1846. https://doi.org/10.1021/acs.joc.9b01913

APA Citation style: Niedek, D., Erb, F., Topp, C., Seitz, A., Wende, R., Eckhardt, A., Kind, J., Herold, D., Thiele, C., & Schreiner, P. (2020). In Situ Switching of Site-Selectivity with Light in the Acetylation of Sugars with Azopeptide Catalysts. The Journal of Organic Chemistry. 85(4), 1835-1846. https://doi.org/10.1021/acs.joc.9b01913