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New chemo- and biocatalytic methodology is important for the future sustainable synthesis of essential molecules. Transition metal catalysis enables the late-stage C−H functionalization of some complex molecular scaffolds, providing rapid routes to valuable products, although this is largely dependent on the availability of electronically or sterically predisposed C−H bonds for selective metalation, leaving certain regioselectivities inaccessible. Unlike metal chemocatalysis, enzymes can catalyse C−H bond functionalization, discriminating between near-identical, non-activated C−H bonds, delivering products with exquisite regioselectivity. However, enzymes typically provide access to fewer functionalities than more divergent chemocatalysis. Here we report programmable, regioselective C−H bond functionalization methodologies for the installation of versatile nitrile, amide and carboxylic acid moieties through integration of halogenase enzymes with palladium-catalysed cyanation and subsequent incorporation of nitrile hydratase or nitrilase enzymes. Using two- or three-component chemobiocatalytic systems, the regioselective synthesis of complex target molecules, including pharmaceuticals, can be achieved in a one-pot process operable on a gram scale. C−H bond functionalization methodologies usually rely on substrate-controlled directing-group chemistries to facilitate regioselective activation. Now, chemobiocatalytic cascades are reported that enable catalyst-controlled regioselective access to aryl nitriles, primary amides and carboxylic acids.

Controlling the selectivity of a chemical reaction with external stimuli is common in thermal processes, but rare in visible‐light photocatalysis. Here we show that the redox potential of a carbon nitride photocatalyst (CN‐OA‐m) can be tuned by changing the irradiation wavelength to generate electron holes with different oxidation potentials. This tuning was the key to realizing photo‐chemo‐enzymatic cascades that give either the (S)‐ or the (R)‐enantiomer of phenylethanol. In combination with an unspecific peroxygenase from Agrocybe aegerita, green light irradiation of CN‐OA‐m led to the enantioselective hydroxylation of ethylbenzene to (R)‐1‐phenylethanol (99 % ee). In contrast, blue light irradiation triggered the photocatalytic oxidation of ethylbenzene to acetophenone, which in turn was enantioselectively reduced with an alcohol dehydrogenase from Rhodococcus ruber to form (S)‐1‐phenylethanol (93 % ee)., Green or blue? The wavelength controls the outcome. Chromoselective activation of a carbon nitride generates electron holes with different oxidation potentials that are used for selective oxidation processes. By coupling the photocatalytic reactions with biocatalysis the (S)‐ or the (R)‐enantiomer of 1‐phenylethanol was synthesized stereoselectively.

Having identified inconsistencies when repeating literature examples of photochemical transformations and difficulties recreating experimental setups, we devised several criteria that an ideal labscale reactor should achieve. Herein, we introduce a versatile photoreactor for high throughput screening, preparative scale batch reactions and continuous processing, all with a single light source. The reactor utilizes interchangeable arrays of pseudo-monochromatic high-power LEDs in a range of synthetically useful wavelengths, combined with excellent temperature control. Moreover, light intensity can be modulated in an accurate and straightforward manner. This system has subsequently been tested on a range of literature methodologies.

Several biocatalytic approaches for the preparation of optically pure methyl 3-oxocyclohexanecarboxylates (S)-, (R)-1 and 3-oxocyclohexanecarbonitriles (S)-, (R)-2 have been successfully demonstrated. Screening of reaction-focused enzyme collections was used to identify initial hits using three enzymatic strategies. Reaction optimization and scale-up enabled the production of chiral intermediates for route scouting efforts on scales of up to 100 g. The enzymes applied in these processes (lipases, enoate reductases, and nitrilases) have been shown to be robust catalysts for drug manufacturing and represent a green alternative to conventional methods to access these chiral cyclohexanone building blocks.

A mild one-pot methodology has been developed to deracemise rac-2-phenyl-1-propanol by combining the use of non-selective laccase/TEMPO-mediated oxidation with enantioselective bioreduction of the racemic aldehyde intermediate under dynamic conditions. The process was easily scalable and stereocontrollable by selecting the suitable biocatalyst.

An efficient and high yield protocol for the synthesis and separation of 3'- and/or 5'-protected alpha-2'-deoxynucleosides has been developed through regioselective acylation/deacylation processes catalyzed by enzymes. Pseudomonas cepacia lipase (PSL-C) was found to be highly chemo- and regioselective toward the 3'-position of the beta-2'-deoxynucleoside derivatives, whereas PSL-C displayed opposite selectivity toward the 5'-position for the corresponding alpha-anomer. The successful application of this protocol was demonstrated by a convenient separation of an alpha/beta-mixture of thymidine derivatives from an industrial waste stream. Furthermore, this technique was also applied for the separation of an anomeric mixture of 2'-deoxy-2'-fluoro-alpha/beta-arabinonucleosides that are useful building blocks for the antisense constructs.

An easy, efficient, and scalable chemoenzymatic strategy for the synthesis of 3‘-O-dimethoxytrityl-2‘-deoxynucleosides has been developed. A key feature of this approach is the regioselective synthesis of 5‘-O-levulinyl-2‘-deoxynucleosides through enzymatic acylation in the presence of Candida antarctica lipase B. In addition, it was observed that the deblocking of levulinyl group from the 5‘-position is perfectly compatible with conventional base protecting groups. To demonstrate the scalability of this method, 3‘-O-dimethoxytritylthymidine (4a) was synthesized on 25-g scale. These monomers (4a−d) are useful building blocks for the synthesis of oligonucleotides.

A series of enantiopure hydroxy esters and lactones has been synthesized in a chemodivergent manner via alcohol dehydrogenase (ADH) reduction of the corresponding keto esters by means of cascade or tandem protocols. Thus, ADH from Rhodococcus ruber (ADH-A) or Lactobacillus brevis (LBADH) afforded both antipodes in a very selective way when dealing with small derivatives. With bulkier substrates, ADH from Ralstonia sp. (RasADH) was successfully employed to achieve the synthesis of enantioenriched γ- or δ-hydroxy esters. To isolate the corresponding lactones, two different approaches were followed: a cascade reaction by spontaneous cyclization of the hydroxy ester intermediate, or a one-pot two-step tandem protocol. Moreover, a chemoenzymatic route was designed to obtain a chiral brominated lactone, which enabled further modifications in a sequential fashion by Pd-catalyzed reactions, affording relevant functionalized lactones.

Regioselective syntheses of several O-crotonyl 2′-deoxynucleoside derivatives have been efficiently achieved using a biocatalytic methodology. While Candida antarctica lipase B (CAL-B) afforded the 5′-O-acylated compounds, immobilized lipase from Pseudomonas cepacia (PSL-C) provided the 3′-O-crotonylated analogs. Since classical chemical approaches did not work appropriately due to side isomerization reactions, a mixture of both lipases was used to achieve a useful synthetic route toward diacylated nucleosides.

Financial support from the Spanish Ministerio de Ciencia e Innovacion (MICINN-12-CTQ2011-24237), the Principado de Asturias (SV-PA-13-ECOEMP-42 and SV-PA-13-ECOEMP-43) and the Universidad de Oviedo (UNOV-13-EMERG-01 and UNOV-13-EMERG-07) is gratefully acknowledged. I. L. acknowledges MICINN for his research contract under the Ramón y Cajal Program. We thank Professor Dimas Suárez (University of Oviedo) for ab initio calculations and helpful discussions.