Regioselective Biocatalytic Transformations Employing Transaminases and Tyrosine Phenol Lyases

Stereoselective amino acid synthesis by synergistic photoredox-pyridoxal radical biocatalysis

Developing synthetically useful enzymatic reactions that are not known in biochemistry and organic chemistry is an important challenge in biocatalysis. Through the synergistic merger of photoredox catalysis and pyridoxal 5'-phosphate (PLP) biocatalysis, we developed a pyridoxal radical biocatalysis approach to prepare valuable noncanonical amino acids, including those bearing a stereochemical dyad or triad, without the need for protecting groups. Using engineered PLP enzymes, either enantiomeric product could be produced in a biocatalyst-controlled fashion. Synergistic photoredox-pyridoxal radical biocatalysis represents a powerful platform with which to discover previously unknown catalytic reactions and to tame radical intermediates for asymmetric catalysis.

Transaminase-mediated chiral selective synthesis of (1R)-(3-methylphenyl)ethan-1-amine from 1-(3-methylphenyl)ethan-1-one: process minutiae, optimization, characterization and 'What If studies'

Transaminases capable of carrying out chiral selective transamination of 1-(3-methylphenyl)ethan-1-one to (1R)-(3-methylphenyl)ethan-1-amine were screened, and ATA-025 was the best enzyme, while dimethylsulfoxide (10% V/V) was the best co-solvent for said bioconversion. The variables such as enzyme loading, substrate loading, temperature, and pH for development of process displaying maximum conversion with good product formation and higher yield were optimized. The ambient processing conditions were 10% enzyme loading/50 g/L substrate loading/45 °C/pH 8.0, and 5% enzyme loading/36.78 g/L substrate loading/42.66 °C/pH 8.2 displaying maximum conversion 99.01 ± 2.47% and 96.115 ± 1.97%, and 76.93 ± 1.05% and 73.12 ± 1.04% yield with one factor at a time approach and numerical optimization with Box Behnken Design, respectively. In the final optimized reaction, ATA-025 showed the highest 99.22 ± 2.61% conversion, 49.55 g/L product formation, with an actual product recovery of 38.16 g corresponding to a product yield 77.03 ± 1.01% with respect to the product formed after reaction. The purity of recovered product (1R)-(3-methylphenyl)ethan-1-amine formed was ≥ 99% (RP-HPLC), and chiral purity ≥ 98.5% (Chiral-GC), and it was also confirmed and characterized with instrumental methods using boiling point, LC-MS, ATR-FTIR, and ¹H NMR. The findings of 'What If' studies performed by investigating timely progress of reaction on gram scale by drastically changing the process parameters revealed a substantial modification in process variables to achieve desired results. (1R)-(3-methylphenyl)ethan-1-amine synthesized by green, facile and novel enzymatic approach with an optimized process could be used for synthesis of different active pharma entities.

Shortening Synthetic Routes to Small Molecule Active Pharmaceutical Ingredients Employing Biocatalytic Methods

Biocatalysis, using enzymes for organic synthesis, has emerged as powerful tool for the synthesis of active pharmaceutical ingredients (APIs). The first industrial biocatalytic processes launched in the first half of the last century exploited whole-cell microorganisms where the specific enzyme at work was not known. In the meantime, novel molecular biology methods, such as efficient gene sequencing and synthesis, triggered breakthroughs in directed evolution for the rapid development of process-stable enzymes with broad substrate scope and good selectivities tailored for specific substrates. To date, enzymes are employed to enable shorter, more efficient, and more sustainable alternative routes toward (established) small molecule APIs, and are additionally used to perform standard reactions in API synthesis more efficiently. Herein, large-scale synthetic routes containing biocatalytic key steps toward >130 APIs of approved drugs and drug candidates are compared with the corresponding chemical protocols (if available) regarding the steps, reaction conditions, and scale. The review is structured according to the functional group formed in the reaction.

Synthesis of Sitagliptin Intermediate by a Multi-Enzymatic Cascade System Using Lipase and Transaminase With Benzylamine as an Amino Donor

Herein, we report the development of a multi-enzyme cascade using transaminase (TA), esterase, aldehyde reductase (AHR), and formate dehydrogenase (FDH), using benzylamine as an amino donor to synthesize the industrially important compound sitagliptin intermediate. A panel of 16 TAs was screened using ethyl 3-oxo-4-(2,4,5-trifluorophenyl) butanoate as a substrate (1). Amongst these enzymes, TA from Roseomonas deserti (TARO) was found to be the most suitable, showing the highest activity towards benzylamine (∼70%). The inhibitory effect of benzaldehyde was resolved by using AHR from Synechocystis sp. and FDH from Pseudomonas sp., which catalyzed the conversion of benzaldehyde to benzyl alcohol at the expense of NAD(P)H. Reaction parameters, such as pH, buffer system, and concentration of amino donor, were optimized. A single whole-cell system was developed for co-expressing TARO and esterase, and the promoter engineering strategy was adopted to control the expression level of each biocatalyst. The whole-cell reactions were performed with varying substrate concentrations (10-100 mM), resulting in excellent conversions (ranging from 72 to 91%) into the desired product. Finally, the applicability of this cascade was highlighted on Gram scale, indicating production of 70% of the sitagliptin intermediate with 61% isolated yield. The protocol reported herein may be considered an alternative to existing methods with respect to the use of cheaper amine donors as well as improved synthesis of (R) and (S) enantiomers with the use of non-chiral amino donors.

An Integrated Cofactor/Co-Product Recycling Cascade for the Biosynthesis of Nylon Monomers from Cycloalkylamines

We report a highly atom-efficient integrated cofactor/co-product recycling cascade employing cycloalkylamines as multifaceted starting materials for the synthesis of nylon building blocks. Reactions using E. coli whole cells as well as purified enzymes produced excellent conversions ranging from >80 and 95 % into desired ω-amino acids, respectively with varying substrate concentrations. The applicability of this tandem biocatalytic cascade was demonstrated to produce the corresponding lactams by employing engineered biocatalysts. For instance, ϵ-caprolactam, a valuable polymer building block was synthesized with 75 % conversion from 10 mM cyclohexylamine by employing whole-cell biocatalysts. This cascade could be an alternative for bio-based production of ω-amino acids and corresponding lactam compounds.

Production of Bulk Chemicals with Biocatalysis: Drivers and Challenges Reflected in Recent Industrial Granted Patents (2015-2020)

The application of biocatalysis and White Biotechnology tools in chemical areas concerning the production of bulk compounds and other related low-added value products (with high volumes) has been gaining importance in recent years. The expected drivers of biocatalysis for these sectors are energy savings, regioselectivity (leading to cleaner products), the possibility of using thermolabile substrates, as well as the generation of less by-products and manageable wastes. This paper explores some recent industrial granted patents related to biocatalysis and bulk chemicals. Several patents have been identified in fields such as biodiesel and esterification reactions, and sugar or furan chemistry. Overall, innovative strategies involve the identification of novel enzymes, the set-up of improved immobilization methods, as well as novel reactor designs that can offer improved performances and economics. The reported examples indicate that biocatalysis can certainly offer opportunities for these areas as well, far from the typical pharmaceutical and fine chemical applications often reported in the literature.

Overview on Multienzymatic Cascades for the Production of Non-canonical α-Amino Acids

The 22 genetically encoded amino acids (AAs) present in proteins (the 20 standard AAs together with selenocysteine and pyrrolysine), are commonly referred as proteinogenic AAs in the literature due to their appearance in ribosome-synthetized polypeptides. Beyond the borders of this key set of compounds, the rest of AAs are generally named imprecisely as non-proteinogenic AAs, even when they can also appear in polypeptide chains as a result of post-transductional machinery. Besides their importance as metabolites in life, many of D-α- and L-α-"non-canonical" amino acids (NcAAs) are of interest in the biotechnological and biomedical fields. They have found numerous applications in the discovery of new medicines and antibiotics, drug synthesis, cosmetic, and nutritional compounds, or in the improvement of protein and peptide pharmaceuticals. In addition to the numerous studies dealing with the asymmetric synthesis of NcAAs, many different enzymatic pathways have been reported in the literature allowing for the biosynthesis of NcAAs. Due to the huge heterogeneity of this group of molecules, this review is devoted to provide an overview on different established multienzymatic cascades for the production of non-canonical D-α- and L-α-AAs, supplying neophyte and experienced professionals in this field with different illustrative examples in the literature. Whereas the discovery of new or newly designed enzymes is of great interest, dusting off previous enzymatic methodologies by a "back and to the future" strategy might accelerate the implementation of new or improved multienzymatic cascades.

Biocatalysis: Chemical Biosynthesis

Biocatalysis is very appealing for industry because it allows the synthesis of products that are not accessible by chemical synthesis, use of alternative raw materials, lower operating costs, low fixed cost infrastructure and improved eco-efficiency [...]

PLP-dependent enzymes as important biocatalysts for the pharmaceutical, chemical and food industries: a structural and mechanistic perspective

PLP-dependent enzymes described on this review are attractive targets for enzyme engineering towards their application in an industrial biotechnology framework.