Application of Transaminases in a Disperse System for the Bioamination of Hydrophobic Substrates

Transaminase-catalysis to produce trans-4-substituted cyclohexane-1-amines including a key intermediate towards cariprazine

Cariprazine-the only single antipsychotic drug in the market which can handle all symptoms of bipolar I disorder-involves trans-4-substituted cyclohexane-1-amine as a key structural element. In this work, production of trans-4-substituted cyclohexane-1-amines was investigated applying transaminases either in diastereotope selective amination starting from the corresponding ketone or in diastereomer selective deamination of their diasteromeric mixtures. Transaminases were identified enabling the conversion of the cis-diastereomer of four selected cis/trans-amines with different 4-substituents to the corresponding ketones. In the continuous-flow experiments aiming the cis diastereomer conversion to ketone, highly diastereopure trans-amine could be produced (de > 99%). The yield of pure trans-isomers exceeding their original amount in the starting mixture could be explained by dynamic isomerization through ketone intermediates. The single transaminase-catalyzed process-exploiting the cis-diastereomer selectivity of the deamination and thermodynamic control favoring the trans-amines due to reversibility of the steps-allows enhancement of the productivity of industrial cariprazine synthesis.

Lipase-Catalyzed Kinetic Resolution of Alcohols as Intermediates for the Synthesis of Heart Rate Reducing Agent Ivabradine

Ivabradine (Corlanor®), is a chiral benzocycloalkane currently employed and commercialized for the treatment of chronic stable angina pectoris and for the reduction in sinus tachycardia. The eutomer (S)-ivabradine is usually produced via chiral resolution of intermediates, by employing enantiopure auxiliary molecules or through preparative chiral HPLC separations. Recently, more sustainable biocatalytic approaches have been reported in literature for the preparation of the chiral amine precursor. In this work, we report on a novel biocatalyzed pathway, via a resolution study of a key alcohol intermediate used as a precursor of the chiral amine. After screening several enzymatic reaction conditions, employing different lipases and esterases both for the esterification and hydrolysis reactions, the best result was achieved with Pseudomonas cepacia Lipase and the final product was obtained in up to 96:4 enantiomeric ratio (e.r.) of an ivabradine alcohol precursor. This enantiomer was then efficiently converted into the desired amine in a facile three step synthetic sequence.

Stabilization of ω-transaminase from Pseudomonas fluorescens by immobilization techniques

Transaminases are a class of enzymes with promising applications for the preparation and resolution of a vast diversity of valued amines. Their poor operational stability has fueled many investigations on its stabilization due to their biotechnological relevance. In this work, we screened the stabilization of the tetrameric ω-transaminase from Pseudomonas fluorescens (PfωTA) through both carrier-bound and carrier-free immobilization techniques. The best heterogeneous biocatalyst was the PfωTA immobilized as cross-linked enzyme aggregates (PfωTA-CLEA) which resulted after studying different parameters as the precipitant, additives and glutaraldehyde concentrations. The best conditions for maximum recovered activity (29 %) and maximum thermostability at 60 ºC and 70 ºC (100 % and 71 % residual activity after 1 h, respectively) were achieved by enzyme precipitation with 90% acetone or ethanol, in presence of BSA (100 mg/mL) and employing glutaraldehyde (100 mM) as cross-linker. Studies on different conditions for PfωTA-CLEA preparation yielded a biocatalyst that exhibited 31 and 4.6 times enhanced thermal stability at 60 °C and 70 °C, respectively, compared to its soluble counterpart. The PfωTA-CLEA was successfully used in the bioamination of 4-hydroxybenzaldehyde to 4-hydroxybenzylamine. To the best of our knowledge, this is the first report describing a transaminase cross-linked enzyme aggregates as immobilization strategy to generate a biocatalyst with outstanding thermostability.