Efficient asymmetric synthesis of 1-cyano-tetrahydroisoquinolines from lipase dual activity and opposite enantioselectivities in α-Aminonitrile resolution

Lipase-Catalyzed Strategies for the Preparation of Enantiomeric THIQ and THβC Derivatives: Green Aspects

This report reviews the most important lipase-catalyzed strategies for the preparation of pharmaceutically and chemically important tetrahydroisoquinoline and tetrahydro-β-carboline enantiomers through O-acylation of the primary hydroxy group, N-acylation of the secondary amino group, and COOEt hydrolysis of the corresponding racemic compounds with simple molecular structure, which have been reported during the last decade. A brief introduction describes the importance and synthesis of tetrahydroisoquinoline and tetrahydro-β-carboline derivatives, and it formulates the objectives of this compilation. The strategies are presented in chronological order, classified according to function of the reaction type, as kinetic and dynamic kinetic resolutions, in the main text. These reactions result in the desired products with excellent ee values. The pharmacological importance of the products together with their synthesis is given in the main text. The enzymatic hydrolysis of the hydrochloride salts as racemates of the starting amino carboxylic esters furnished the desired enantiomeric amino carboxylic acids quantitatively. The enzymatic reactions, performed in tBuOMe or H2O as usable solvents, and the transformations carried out in a continuous-flow system, indicate clear advantages, including atom economy, reproducibility, safer solvents, short reaction time, rapid heating and compression vs. shaker reactions. These features are highlighted in the main text.

Diversifying Arena of Drug Synthesis: In the Realm of Lipase Mediated Waves of Biocatalysis

Hydrolases, being most prominent enzymes used in industrial processes have left no stone unturned in fascinating the pharmaceutical industry. Lipases, being a part of acyl hydrolases are the ones that function similarly to esterases (except an interfacial action) wherein they generally catalyze the hydrolysis of ester bonds. Be it in terms of stereoselectivity or regioselectivity, lipases have manifested their promiscuous proficiency in rendering biocatalytic drug synthesis and intermediates thereof. Industrial utilization of lipases is prevalent since decades ago, but their distinctive catalytic competencies have rendered them suitable for maneuverability in various tides of biocatalytic industrial process development. Numbers of exquisite catalysts have been fabricated out of lipases using nanobiotechnology whereby enzyme reusability and robustness have been conferred to many of the organic synthesis procedures. This marks a considerable achievement of lipases in the second wave of biocatalysis. Furthermore, in the third wave an advent of genetic engineering has fostered an era of customized lipases for suitable needs. Be it stability or an enhanced efficacy, genetic engineering techniques have ushered an avenue for biocatalytic development of drugs and drug intermediates through greener processes using lipases. Even in the forthcoming concept of co-modular catalytic systems, lipases may be the frontiers because of their astonishing capability to act along with other enzymes. The concept may render feasibility in the development of cascade reactions in organic synthesis. An upcoming wave demands fulfilling the vision of tailored lipase whilst a far-flung exploration needs to be unveiled for various research impediments in rendering lipase as a custom fit biocatalyst in pharmaceutical industry.

Dynamic Covalent Kinetic Resolution

Implemented with the highly efficient concept of Dynamic Kinetic Resolution (DKR), dynamic covalent chemistry can be a useful strategy for the synthesis of enantioenriched compounds. This gives rise to dynamic covalent kinetic resolution (DCKR), a subset of DKR that over the last decades has emerged as increasingly fruitful, with many applications in asymmetric synthesis and catalysis. All DKR protocols are composed of two important parts: substrate racemization and asymmetric transformation, which can lead to yields of >50% with good enantiomeric excesses (ee) of the products. In DCKR systems, by utilizing reversible covalent reactions as the racemization strategy, the substrate enantiomers can be easily interconverted without the presence of any racemase or transition metal catalyst. Enzymes or other chiral catalysts can then be adopted for the resolution step, leading to products with high enantiopurities. This tutorial review focuses on the development of DCKR systems, based on different reversible reactions, and their applications in asymmetric synthesis.

Silva MV, Dias FC, de Souza SP, Leão RAC, de Souza ROMA. Continuous flow dynamic kinetic resolution of rac-1-phenylethanol using a single packed-bed containing immobilized CAL-B lipase and VOSO4 as racemization catalysts

Herein, we report a method for the continuous flow DKR of rac-1-phenylethanol catalyzed by CAL-B and VOSO₄, using a single packed-bed containing both catalysts.

Enzyme classification using complex dynamic hemithioacetal systems

A complex dynamic hemithioacetal system was used in combination with pattern recognition methodology to classify lipases into distinct groups.

A complex dynamic hemithioacetal system was generated for the evaluation of lipase reactivities in organic media. In combination with pattern recognition methodology, twelve different lipases were successfully classified into four distinct groups following their reaction selectivities and reactivities. A probe lipase was further categorized using the training matrix with predicted reactivity.