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An ortho C-methylation/O-glycosylation motif on a hydroxy-coumarin scaffold, selectively installed by biocatalysis

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Abstract

Various bioactive natural products, like the aminocoumarin antibiotics novobiocin and coumermycin, exhibit an aromatic C-methyl group adjacent to a glycosylated phenolic hydroxyl group. Therefore, tailoring of basic phenolic scaffolds to contain the intricate C-methyl/O-glycosyl motif is of high interest for structural and functional diversification of natural products. We demonstrate site-selective 8-C-methylation and 7-O-β-D-glucosylation of 4,5,7-trihydroxy-3-phenyl-coumarin (1) by S-adenosyl-L-methionine dependent C-methyltransferase (from Streptomyces niveus) and uridine 5′-diphosphate glucose dependent glycosyltransferase from apple (Malus × domestica). Both enzymes were characterized and shown to react readily with underivatized 1. However, glucosylation of the ortho-hydroxyl group prevented C-methylation, probably by precluding an essential substrate activation through deprotonation of 7-OH. Therefore, dual modification was only feasible when C-methylation occurred strictly before O-glucosylation. The target product was synthesized in near quantitative yield (98% conversion) from 500 μM 1 and its structure was confirmed by NMR. Combination of C-methyltransferase and O-glycosyltransferase reactions for synthetic tailoring of a natural product through biocatalysis was demonstrated for the first time.

Graphical abstract: An ortho C-methylation/O-glycosylation motif on a hydroxy-coumarin scaffold, selectively installed by biocatalysis

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Publication details

The article was received on 22 Jun 2017, accepted on 05 Sep 2017 and first published on 05 Sep 2017


Article type: Paper
DOI: 10.1039/C7OB01513E
Citation: Org. Biomol. Chem., 2017, Advance Article
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    An ortho C-methylation/O-glycosylation motif on a hydroxy-coumarin scaffold, selectively installed by biocatalysis

    A. Gutmann, M. Schiller, M. Gruber-Khadjawi and B. Nidetzky, Org. Biomol. Chem., 2017, Advance Article , DOI: 10.1039/C7OB01513E

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