Issue 10, 2014

Deracemisation of benzylisoquinoline alkaloids employing monoamine oxidase variants

Abstract

Chemo-enzymatic deracemisation was applied to obtain the (S)-enantiomer of 1-benzylisoquinolines from the racemate in high isolated yield (up to 85%) and excellent optical purity (ee > 97%). The one-pot deracemisation protocol encompassed enantioselective oxidation by a monoamine oxidase (MAO-N) and concomitant reduction of the resulting iminium species by ammonia-borane. The challenge was the oxidation at the sterically demanding chiral centre. Recently developed variants of MAO-N, featuring an enlarged active-site pocket, turned out to be suitable biocatalysts for these substrates. In contrast to previous MAO-N variants, which preferentially converted the (S)-enantiomer, the MAO-N variant D11 used in the present study was found to oxidise all tested benzylisoquinoline substrates with (R)-enantiopreference. The structural determinants of enantioselectivity were investigated by means of protein–ligand docking simulations. The applicability of the deracemisation system was demonstrated on preparative scale (150 mg) for three benzylisoquinoline alkaloids (natural as well as non-natural), including the hypotensive and antispasmodic agent (S)-reticuline.

Graphical abstract: Deracemisation of benzylisoquinoline alkaloids employing monoamine oxidase variants

Supplementary files

Article information

Article type
Paper
Submitted
19 May 2014
Accepted
01 Jul 2014
First published
14 Jul 2014

Catal. Sci. Technol., 2014,4, 3657-3664

Author version available

Deracemisation of benzylisoquinoline alkaloids employing monoamine oxidase variants

J. H. Schrittwieser, B. Groenendaal, S. C. Willies, D. Ghislieri, I. Rowles, V. Resch, J. H. Sattler, E. Fischereder, B. Grischek, W. Lienhart, N. J. Turner and W. Kroutil, Catal. Sci. Technol., 2014, 4, 3657 DOI: 10.1039/C4CY00642A

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