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. 2022 Jan 12;144(1):80-85.
doi: 10.1021/jacs.1c11340. Epub 2021 Dec 23.

An Enzymatic Platform for Primary Amination of 1-Aryl-2-alkyl Alkynes

Zhen Liu  1 , Zi-Yang Qin  1 , Ledong Zhu  2 , Soumitra V Athavale  1 , Arkajyoti Sengupta  2 , Zhi-Jun Jia  1 , Marc Garcia-Borràs  3 , K N Houk  2 , Frances H Arnold  1
Affiliations

An Enzymatic Platform for Primary Amination of 1-Aryl-2-alkyl Alkynes

Zhen Liu et al. J Am Chem Soc. .

Abstract

Propargyl amines are versatile synthetic intermediates with numerous applications in the pharmaceutical industry. An attractive strategy for efficient preparation of these compounds is nitrene propargylic C(sp3)-H insertion. However, achieving this reaction with good chemo-, regio-, and enantioselective control has proven to be challenging. Here, we report an enzymatic platform for the enantioselective propargylic amination of alkynes using a hydroxylamine derivative as the nitrene precursor. Cytochrome P450 variant PA-G8 catalyzing this transformation was identified after eight rounds of directed evolution. A variety of 1-aryl-2-alkyl alkynes are accepted by PA-G8, including those bearing heteroaromatic rings. This biocatalytic process is efficient and selective (up to 2610 total turnover number (TTN) and 96% ee) and can be performed on preparative scale.

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Conflict of interest statement

The authors declare no competing financial interest.

Figures

Figure 1.
Figure 1.
Directed evolution for enantioselective propargylic amination. a) Evolutionary trajectory of PA-G8 for the synthesis of propargyl amine 3a. PA-G8 was evolved through eight rounds of SSM and screening starting from PA-G0. Indicated mutations are relative to PA-G0. The experiments were performed using E. coli (OD600 = 20) that expressed P411 enzymes with 2 mM substrate 1a and 5 mM substrate 2 in M9-N buffer (pH = 8.4) at 10 °C under anaerobic conditions. Performing reactions at 10 °C was found to give higher yields compared to running them at room temperature. Yields were quantified by LC-MS based on the calibration curve of 3a. Enantioselectivities were measured by HPLC on a chiral phase after benzoyl protection. See SI for details. b) The mutated residues (S72, A74, H266, E267, T269, N395, G437, and S438) are highlighted in the active site of P411 variant E10 (PDB ID: 5UCW).
Figure 2.
Figure 2.
a) Substrate scope of enantioselective propargylic amination. The experiments were performed at analytical scale using E. coli (OD600 = 20) that expressed the PA-G8 enzyme with 2 mM substrate (1a–l) and 5 mM substrate 2 in M9-N buffer (pH = 8.4) at 10 °C under anaerobic conditions. Yields were quantified by LC-MS based on the calibration curves of the corresponding reference products. Enantioselectivities were measured by HPLC on a chiral phase after benzoyl protection of the propargyl amine products. See SI for details. b) Preparative-scale synthesis and product derivatization for the determination of absolute stereochemistry. Chiral amides 4a and 4d were obtained from benzoyl protection of amines 3a and 3d. Compound 4a was used to determine the absolute stereochemistry by comparing the optical rotation with the reported value of (R)-4a.
Figure 3.
Figure 3.
DFT computed free energy profile for the iron(II)-porphyrin catalyzed propargylic C(sp3)–H amination using a truncated computational model and substrate 1a. Gibbs free energies are obtained at the B3LYP-D3(BJ)/Def2TZVP/SMD(ε=4)//B3LYP-D3(BJ)/6-31G(d)-SDD(Fe) level of theory, and are given in kcal·mol−1. Key distances and angles are given in Å and degrees, respectively.
Scheme 1.
Scheme 1.
Background and Project Synopsis
See this image and copyright information in PMC

References

    1. Lauder K; Toscani A; Scalacci N; Castagnolo D Synthesis and reactivity of propargylamines in organic chemistry. Chem. Rev 2017, 117, 14091–14200. - PubMed
    1. Zindo FT; Joubert J; Malan SF Propargylamine as functional moiety in the design of multifunctional drugs for neurodegenerative disorders: MAO inhibition and beyond. Future Med. Chem 2015, 7, 609–629. - PubMed
    1. Tardif J-C; L’Allier PL; Ibrahim R; Grégoire JC; Nozza A; Cossette M; Kouz S; Lavoie M-A; Paquin J; Brotz TM; Taub R; Pressacco J Treatment with 5-lipoxygenase inhibitor VIA-2291 (atreleuton) in patients with recent acute coronary syndrome. Circ. Cardiovasc. Imaging 2010, 3, 298–307. - PubMed
    2. Cossy J; Schmitt A; Cinquin C; Buisson D; Belotti D A very short, efficient and inexpensive synthesis of the prodrug form of SC-54701A a platelet aggregation inhibitor. Bioorg. Med. Chem. Lett 1997, 7, 1699–1700. - PubMed
    1. Volkova Y; Baranin S; Zavarzin I A3 coupling reaction in the synthesis of heterocyclic compounds. Adv. Synth. Catal 2021, 363, 40–61.

    1. For selected examples, see:

    2. Hattori G; Matsuzawa H; Miyake Y; Nishibayashi Y Copper-catalyzed asymmetric propargylic substitution reactions of propargylic acetates with amines. Angew. Chem. Int. Ed 2008, 47, 3781–3783. - PubMed
    3. Schmidt NG; Simon RC; Kroutil W Biocatalytic asymmetric synthesis of optically pure aromatic propargylic amines employing ω-transaminases. Adv. Synth Catal 2015, 357, 1815–1821. - PubMed
    4. Chen B-L; Wang B; Lin G-Q Highly diastereoselective addition of alkynylmagnesium chlorides toN-tert-butanesulfinyl aldimines: A practical and general access to chiral α-branched amines. J. Org. Chem 2010, 75, 941–944. - PubMed

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