A Protection Strategy Substantially Enhances Rate and Enantioselectivity in ω‐Transaminase‐Catalyzed Kinetic Resolutions

Abstract

The kinetic resolution of 3-aminopyrrolidine (3AP) and 3-aminopiperidine (3APi) with wtransaminases was facilitated by the application of a protecting group concept. 1-N-Cbz-protected 3-aminopyrrolidine could be resolved with > 99% ee at 50% conversion, the resolution of 1-N-Boc-3-aminopiperidine yielded 96% ee at 55% conversion. The reaction rate was up to 50-fold higher by using protected substrates. Most importantly, enantioselectivity increased remarkably after carbamate protection compared to the unprotected substrates (86 vs. 99% ee). Surprisingly, benzyl protection of 3AP had no influence on enantioselectivity. A possible explanation for this observation could be the different flexibility of the benzyl-or carbamate-protected 3AP as confirmed by NMR spectroscopy.

Connecting Unexplored Protein Crystal Structures to Enzymatic Function

“…3GJU preferred benzylamine over ( S )‐ 6 to a greater extent than the other three enzymes, but displayed only low specific activity. Surprisingly, 1‐ N ‐Boc‐3‐aminopyrrolidine (Boc= tert ‐butoxycarbonyl), which is often not a preferred substrate for ATAs,6, 19 was the best substrate for 3FCR and 3GJU.…”

Asymmetric Synthesis of Optically Pure Pharmacologically Relevant Amines Employing ω‐Transaminases

“…[24][25][26][27] One challenge in asymmetric synthesis employing w-transaminases is to shift the equilibrium to the product side, especially when using an amino acid like alanine as amino donor, since in this case the equilibrium is on the side of the substrates (ketone, alanine) and not on the side of the products (amine, pyruvate); [27] another problem is that the stereoselectivity of the enzyme has to be perfect, which is not always the case for w-transaminases. For this reason, w-transaminases are mainly used for the kinetic resolution of racemic amines, [28][29][30][31][32][33] where enantioselectivity does not necessarily need to be perfect, since at a certain conversion > 50% the ee of the substrate will always approximate > 99%.…”

Use of Immobilized Amine Transaminase from Vibrio fluvialis under Flow Conditions for the Synthesis of (S)‐1‐(5‐Fluoropyrimidin‐2‐yl)‐ethanamine

“…Upon in‐line purification, the target amine was submitted to a HPLC chiral analysis to assess the enantiomeric excess. The absolute configuration of a chiral amino donor has to match the stereospecificity of the ATAs in order to be accepted: this feature explains why transaminases can be employed in the kinetic resolution of racemic amines . For this reason, Vf‐ ATA, which is a ( S )‐selective ATA, should not be able to produce amines with ( R )‐configuration.…”