Engineering an Enantioselective Amine Oxidase for the Synthesis of Pharmaceutical Building Blocks and Alkaloid Natural Products

Abstract

The development of cost-effective and sustainable catalytic methods for the production of enantiomerically pure chiral amines is a key challenge facing the pharmaceutical and fine chemical industries. This challenge is highlighted by the estimate that 40-45% of drug candidates contain a chiral amine, fueling a demand for broadly applicable synthetic methods that deliver target structures in high yield and enantiomeric excess. Herein we describe the development and application of a "toolbox" of monoamine oxidase variants from Aspergillus niger (MAO-N) which display remarkable substrate scope and tolerance for sterically demanding motifs, including a new variant, which exhibits high activity and enantioselectivity toward substrates containing the aminodiphenylmethane (benzhydrylamine) template. By combining rational structure-guided engineering with high-throughput screening, it has been possible to expand the substrate scope of MAO-N to accommodate amine substrates containing bulky aryl substituents. These engineered MAO-N biocatalysts have been applied in deracemization reactions for the efficient asymmetric synthesis of the generic active pharmaceutical ingredients Solifenacin and Levocetirizine as well as the natural products (R)-coniine, (R)-eleagnine, and (R)-leptaflorine. We also report a novel MAO-N mediated asymmetric oxidative Pictet-Spengler approach to the synthesis of (R)-harmicine.

Immobilised whole-cell recombinant monoamine oxidase biocatalysis

“…Recently, Ghislieri et al (2013) designed a toolbox for the development of MAO-N variants applicable in asymmetric synthesis of the generic active pharmaceutical ingredients Solifenacin and Levocetirizine, as well as the natural products (R)-coniine, (R)-eleagnine, (R)-leptaflorine and (R)-harmicine.…”

One-Pot Combination of Metal- and Bio-Catalysis in Water for the Synthesis of Chiral Molecules

“…Accordingly, a one-pot/two-step methodology allowed the direct conversion of diallyl malonates into cyclic monoacid esters in aqueous media (Scheme 13C). Recently, and following this idea (Ru-catalyzed RCM + enzymatic organic transformations), Turner, Castagnolo and co-workers have reported the combination of the Ru-catalyzed ring-closing metathesis of diallyl anilines (to produce the corresponding 3-pyrrolines) and the subsequent biocatalytic aromatization of the resulting heterocycles (mediated by whole cells containing monoamine oxidases MAO-N variants D5, D9 and D11 [82][83][84] or the nicotine oxidase biocatalyst 6-HDNO (HDNO = 6-hydroxy-D-nicotine oxidase) [85]) for the synthesis of pyrroles in aqueous media (Scheme 14) [77]. In this case, and in contrast to the aforementioned results reported by Gröger, the authors firstly parametrized the biocatalytic transformation, thus studying the aromatization of different 3-pyrrolines promoted by monoamine oxidases MAO-N or 6-HDNO (Scheme 14A).…”

Why Leave a Job Half Done? Recent Progress in Enzymatic Deracemizations

“…[114] Furthermore, the development of a new D11 variant, which possessed high activity and excellent stereoselectivity toward bulky substrates, was accomplished. This enzyme was applied to the deracemization of Solefenacin, a competitive muscarinic acetylcholine receptor antagonist, and several Levocetirizine precursors, an antihistamine drug, thus expanding the substrate scope of MAO-N. For instance, the deracemization of 4-chlorobenzhydrylamine for the production of the (R)-configured amine was carried out with excellent enantiomeric excess (97%) and moderate isolated yield (45%, Scheme 18a).…”

“…[115] Scheme 18. a) Deracemization of a Levocitirizine motif using a MAO variant and the ammonia-borane complex. [114] b) Deracemization of β-carbolines using MAO-N-D10 and MAO-N-D11. [115] Using new strategies…”