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The design of a hybrid one-pot tandem protocol through the combination of biodeoximations (promoted by laccase from Trametes versicolor) and s-block polar organometallics (RLi/RMgX) in aqueous media, at room temperature and under air is reported.

Purpose: The goal of this study was to identify second-generation mithramycin analogues that better target the EWS-FLI1 transcription factor for Ewing sarcoma. We previously established mithramycin as an EWS-FLI1 inhibitor, but the compound's toxicity prevented its use at effective concentrations in patients.Experimental Design: We screened a panel of mithralogs to establish their ability to inhibit EWS-FLI1 in Ewing sarcoma. We compared the IC50 with the MTD established in mice to determine the relationship between efficacy and toxicity. We confirmed the suppression of EWS-FLI1 at the promoter, mRNA, gene signature, and protein levels. We established an improved therapeutic window by using time-lapse microscopy to model the effects on cellular proliferation in Ewing sarcoma cells relative to HepG2 control cells. Finally, we established an improved therapeutic window using a xenograft model of Ewing sarcoma.Results: EC-8105 was found to be the most potent analogue and was able to suppress EWS-FLI1 activity at concentrations nontoxic to other cell types. EC-8042 was substantially less toxic than mithramycin in multiple species but maintained suppression of EWS-FLI1 at similar concentrations. Both compounds markedly suppressed Ewing sarcoma xenograft growth and inhibited EWS-FLI1 in vivo.Conclusions: These results provide a basis for the continued development of EC-8042 and EC-8105 as EWS-FLI1 inhibitors for the clinic. Clin Cancer Res; 22(16); 4105–18. ©2016 AACR.

Table S1, PCR primers used in gene signature panel. Table S2, Evidence for selection of each gene as an EWS-FLI1 target. S3A Mean fold change in expression of NR0B1 as a function of GAPDH (2Î"Î"CT) following treatment with MMA or EC-8105. Data is the average of 3 independent experiments as measured by qPCR. S3B Mean fold change in expression of EWS-FLI1-induced targets as a function of GAPDH (2Î"Î"CT) for treatment with an siRNA targeted at the breakpoint of EWS/FLI1 for 24 h. Data is the average of 3 independent experiments as measured by qPCR S3C Mean fold change in expression of EWS-FLI1-suppressed targets as a function of GAPDH (2Î"Î"CT) for treatment with an siRNA targeted at the breakpoint of EWS-FLI1for 24 h. Data is the average of 3 independent experiments as measured by qPCR S4A: Structures and NSC numbers of mithramycin analogs S4A: Structures and NSC numbers of mithramycin analogs (cont'd). S4C. Allometric scaling estimates for dosing as a function of weight of an organism for mithramycin (MMA) and EC-8042. (see text for reference). S5A Pearson correlation analysis showing similar responses of the PPTP panel of cell lines for EC-8105 and EC-8042 relative to mithramycin. S5B IC50 values for cell lines in PPTP. Columns are all cell lines tested, exclusion of rhabdoid tumor (minus rhabdoid) and exclusion of rhabdoid tumor and acute lymphoblastic leukemia cell lines (minus rhabdoid and ALL). The statistics are shown in boxes at the bottom. S5C Graph of IC50 as a function of p53 status. Cell lines with wild-type p53 (P53 wt) were more sensitive to treatment with mithramycin (MMA) and EC-8105 than lines with mutant p53 (P53 Mut) across the entire PPTP panel of cell lines independent of histology. Note there was no difference with the non-DNA damaging analogy, EC-8042. S6 Prediction plot showing mean tumor volume as a function of days of treatment with EC-8105 (1.0 mg/kg IP, M/W/F schedule, 8 doses). Thick, dotted lines represent mean tumor growth and the individual lines in the back represent the individual tumor growth by cohort. S7 Weight of each mouse in cohort of EC-8105 treated mice (black lines) treated on a 1.5 mg/kg/dose IV Q3D X 8 doses schedule relative to weight change of control mice (grey line). S8 Survival curves for control mice (black) relative to EC-8042-treated mice (grey) treated at 24 mg/kg dose X 8 either intravenously (S8A) or intraperitoneal (S8B). Arrows indicate end of treatment. S9. Response of mice treated with 24 mg/kg/dose EC-8042 IP M, W, F X8 (S9A). Regression of tumors for every mouse mouse in the cohort. Each line represents an individual mouse. Asterisks (*) highlight treatment days. S9B Mean tumor volume (+/- SEM) of every mouse in the control cohort (3177 mm3 +/- 308.2) relative to the EC-8042-treated cohort (422.5 mm3 +/- 48) on day 11 of treatment (P < 0.0001). S10: Suppression of NR0B1 staining in cells treated with 1.5 mg/kg EC-8105 IV, 48 hours after treatment. Three representative sections are shown stained for NR0B1 (red) or DAPI (blue) since the tumors were large and showed a range of staining.

The one-pot/two-step combination of enzymes and polar organometallic chemistry in aqueous media is for the first time presented as a proof-of-concept study. The unprecedented combination of the catalytic oxidation of secondary alcohols by the system laccase/TEMPO with the ultrafast addition (3 s reaction time) of polar organometallic reagents (RLi/RMgX) to the in situ formed ketones, run under air at room temperature, allows the straightforward and chemoselective synthesis of tertiary alcohols with broad substrate scope and excellent conversions (up to 96%).

Highly polarized organometallic compounds of s-block elements are added smoothly to chiral N-tert-butanesulfinyl imines in the biodegradable d-sorbitol/choline chloride eutectic mixture, thereby granting access to enantioenriched primary amines after quantitatively removing the sulfinyl group. The practicality of the method is further highlighted by proceeding at ambient temperature and under air, with very short reaction times (2 min), enabling the preparation of diastereoisomeric sulfinamides in very good yields (74-98 %) and with a broad substrate scope, and the possibility of scaling up the process. The method is demonstrated in the asymmetric syntheses of both the chiral amine side-chain of (R,R)-Formoterol (96 % ee) and the pharmaceutically relevant (R)-Cinacalcet (98 % ee).

A series of optically active β-hydroxy sulfones has been obtained through an oxosulfonylation-stereoselective reduction sequence in aqueous medium. Firstly, β-keto sulfones were synthesized from arylacetylenes and sodium sulfinates to subsequently develop the carbonyl reduction in a highly selective fashion using alcohol dehydrogenases as biocatalysts. Optimization of the chemical oxosulfonylation reaction was investigated, finding inexpensive iron(III) chloride hexahydrate (FeCl3 ⋅ 6H2 O) as the catalyst of choice. The selection of isopropanol in the alcohol-water media resulted in high compatibility with the enzymatic process for enzyme cofactor recycling purposes, providing a straightforward access to both (R)- and (S)-β-hydroxy sulfones. The practical usefulness of this transformation was illustrated by describing the synthesis of a chiral intermediate of Apremilast. Interestingly, the development of a chemoenzymatic cascade approach avoided the isolation of β-keto sulfone intermediates, which allowed the preparation of chiral β-hydroxy sulfones in high conversion values (83-94 %) and excellent optical purities (94 to >99 % ee).

A tandem protocol to access tertiary alcohols has been developed which combines the organocatalytic oxidation of secondary alcohols to ketones followed by their chemoselective addition by several RLi reagents. Reactions take place at room temperature, under air and in aqueous solutions, a trio of conditions that are typically forbidden in polar organometallic chemistry.

The efficient multifunctionalization by one-pot or cascade catalytic systems has developed as an important research field, but is often challenging due to incompatibilities or cross-reactivities of the catalysts leading to side product formation. Herein we report the stereoselective preparation of cis- and trans-4-aminocyclohexanol from the potentially bio-based precursor 1,4-cyclohexanedione. We identified regio- and stereoselective enzymes catalyzing reduction and transamination of the diketone, which can be performed in a one-pot sequential or cascade mode. For this, we identified regioselective keto reductases for the selective mono reduction of the diketone to give 4-hydroxycyclohexanone. The system is modular and by choosing stereocomplementary amine transaminases, both cis- and trans-4-aminocyclohexanol were synthesized with good to excellent diastereomeric ratios. Furthermore, we identified an amine transaminase that produces cis-1,4-cyclohexanediamine with diastereomeric ratios >98 : 2. These examples highlight that the high selectivity of enzymes enable short and stereoselective cascade multifunctionalizations to generate high-value building blocks from renewable starting materials. Introduction

Phenolic acid decarboxylase from Bacillus subtilis (BsPAD) converts several p-hydroxycinnamic acid derivatives into the corresponding p-hydroxystyrenes, which are considered to be promising bio-bas...

An efficient and selective N-functionalization of amides is first reported via a CuI-catalyzed Goldberg-type C–N coupling reaction between aryl iodides and primary/secondary amides run either in Deep Eutectic Solvents (DESs) or water as sustainable reaction media, under mild and bench-type reaction conditions (absence of protecting atmosphere). Higher activities were observed in an aqueous medium, though the employment of DESs expanded and improved the scope of the reaction to include also aliphatic amides. Additional valuable features of the reported protocol include: (i) the possibility to scale up the reaction without any erosion of the yield/reaction time; (ii) the recyclability of both the catalyst and the eutectic solvent up to 4 consecutive runs; and (iii) the feasibility of the proposed catalytic system for the synthesis of biologically active molecules.

The amazing challenge of orchestrate enzymatic cascades (multi-enzymatic or chemo-enzymatic) usually faces numerous issues to be addressed. Together with the advances in synthetic biology, materials science and protein engineering, the discovery of new reaction media represents a valuable tool in the search towards cost-efficient and sustainable enzymatic cascades in an industrial setting. This chapter showcases the recent developments on the implementation of the so-called non-conventional media in such processes.

The Meyer-Schuster rearrangement of propargylic alcohols into α,β-unsaturated carbonyl compounds has been revisited by setting up an atom-economic process catalyzed by a deep eutectic solvent FeCl3·6H2O/glycerol. Isomerizations take place smoothly, at room temperature, under air and with short reaction times. The unique solubilizing properties of the eutectic mixture enabled the use of a substrate concentration up to 1.0 M with the medium being recycled up to ten runs without any loss of catalytic activity.

Several chemoenzymatic routes have been explored for the preparation of cinacalcet, a calcimimetic agent. Transaminases (TAs) and ketoreductases (KREDs) turned out to be useful biocatalysts for the preparation of key optically active precursors. Thus, the asymmetric amination of 1-acetonaphthone yielded an enantiopure (R)-amine, which can be alkylated in one step to yield cinacalcet. Alternatively, the bioreduction of the same ketone resulted in an enantiopure (S)-alcohol, which was easily converted into the previous (R)-amine. In addition, the reduction was efficiently performed with the KRED and its cofactor co-immobilized on the same porous surface. This self-sufficient heterogeneous biocatalyst presented an accumulated total turnover number (TTN) for the cofactor of 675 after 5 consecutive operational cycles. Finally, in a preparative scale synthesis the TA-based approach was performed in aqueous medium and led to enantiopure cinacalcet in two steps and 50% overall yield.

Multi-step one-pot chemoenzymatic cascade reactions (mo-CECRs) bridging chemo- and bio-catalysis can not only accomplish chemical transformations with minimized purification steps, low cost and improved stereochemical control, but also enhance reactivity and outcomes through the cooperative effect of multiple catalysts. Despite the attractiveness of the concept which meets the principles of green and sustainable chemistry, the establishment of such catalytic networks faces important challenges due to the incompatibilities between different catalytic disciplines. The purpose of this review is to chart progress on mo-CECRs, including temporal compartmentalization, spatial compartmentalization and chemo-bio nanoreactors, with an emphasis on platform methods and technologies involved. The perspectives on future challenges and strategies in this burgeoning research are declared. This review may provide guidance for the design of new and robust mo-CECRs.

The combination of the metal-catalyzed cycloisomerization of alkynes containing a tethered nucleophile as substituent in aqueous media (followed by the spontaneous hydrolysis, hydroalkoxylation, or aminolysis of the transiently formed five-membered heterocycles) with the subsequent enantioselective ketone bioreduction (mediated by KREDs) has been achieved. The overall transformations, which formally involve a three-step one-pot reaction, provide a variety of enantiopure valuable molecules (e.g., 1,4-diols, lactones, and γ-hydroxy-carbonyl compounds (carboxylic acids, esters, and amides)) with high conversions and enantioselectivities and under mild reaction conditions, disclosing the concept of integrated metal-catalyzed cycloisomerizations of alkynes and enzymatic catalysis in water.

The self-assembly of styrene-type olefins into the corresponding stilbenes was conveniently performed in the Deep Eutectic Solvent (DES) mixture 1ChCl/2Gly under air and in the absence of hazardous organic co-solvents using a one-pot chemo-biocatalytic route. Here, an enzymatic decarboxylation of p-hydroxycinnamic acids sequentially followed by a ruthenium-catalyzed metathesis of olefins has been investigated in DES. Moreover, and to extend the design of chemoenzymatic processes in DESs, we also coupled the aforementioned enzymatic decarboxylation reaction to now concomitant Pd-catalyzed Heck-type C-C coupling to produce biaryl derivatives under environmentally friendly reaction conditions.

Amine transaminases (ATAs) are used to synthesize enantiomerically pure amines, which are building blocks for pharmaceuticals and agrochemicals. R‐selective ATAs belong to the fold type IV PLP‐dependent enzymes, and different sequence‐, structure‐ and substrate scope‐based features have been identified in the past decade. However, our knowledge is still restricted due to the limited number of characterized (R)‐ATAs, with additional bias towards fungal origin. We aimed to expand the toolbox of (R)‐ATAs and contribute to the understanding of this enzyme subfamily. We identified and characterized four new (R)‐ATAs. The ATA from Exophiala sideris contains a motif characteristic for d‐ATAs, which was previously believed to be a disqualifying factor for (R)‐ATA activity. The crystal structure of the ATA from Shinella is the first from a Gram‐negative bacterium. The ATAs from Pseudonocardia acaciae and Tetrasphaera japonica are the first characterized (R)‐ATAs with a shortened/missing N‐terminal helix. The active‐site charges vary significantly between the new and known ATAs, correlating with their diverging substrate scope., Diversifying: The toolbox of R‐selective amine transaminases (ATAs) has been expanded by an ATA containing a motif characteristic for d‐ATAs, two ATAs with a shortened/missing N‐terminal helix and the first ATA with known structure from a Gram‐negative bacterium. Their active site charges vary significantly compared to known ATAs correlating with their diverging substrate scope.

A novel series of enantiopure naphthalimide-cycloalkanediamine conjugates were designed, synthetized and evaluated for in vitro cytotoxicity against human colon adenocarcinoma (LoVo), human lung adenocarcinoma (A549), human cervical carcinoma (Hela) and human promyelocytic leukemia cell lines (HL-60). The cytotoxicity of the compounds was highly dependent on size and relative stereochemistry of the cycloalkyl ring as well as length of the spacer. By contrast, any kind of enantioselection was observed for each pair of enantiomers. Flow cytometric analysis indicated that compounds 22 and 23 could effectively induce G2/M arrest in the four previous cell lines despite a mild apoptotic effect.

Purpose: The goal of this study was to identify second-generation mithramycin analogues that better target the EWS-FLI1 transcription factor for Ewing sarcoma. We previously established mithramycin as an EWS-FLI1 inhibitor, but the compound's toxicity prevented its use at effective concentrations in patients. Experimental Design: We screened a panel of mithralogs to establish their ability to inhibit EWS-FLI1 in Ewing sarcoma. We compared the IC50 with the MTD established in mice to determine the relationship between efficacy and toxicity. We confirmed the suppression of EWS-FLI1 at the promoter, mRNA, gene signature, and protein levels. We established an improved therapeutic window by using time-lapse microscopy to model the effects on cellular proliferation in Ewing sarcoma cells relative to HepG2 control cells. Finally, we established an improved therapeutic window using a xenograft model of Ewing sarcoma. Results: EC-8105 was found to be the most potent analogue and was able to suppress EWS-FLI1 activity at concentrations nontoxic to other cell types. EC-8042 was substantially less toxic than mithramycin in multiple species but maintained suppression of EWS-FLI1 at similar concentrations. Both compounds markedly suppressed Ewing sarcoma xenograft growth and inhibited EWS-FLI1 in vivo. Conclusions: These results provide a basis for the continued development of EC-8042 and EC-8105 as EWS-FLI1 inhibitors for the clinic. Clin Cancer Res; 22(16); 4105–18. ©2016 AACR.

The first application of Deep Eutectic Solvents (DESs) in asymmetric bioamination of ketones has been accomplished. The amine transaminases (ATAs) turned out to be particularly stable in DES-buffer mixtures at a percentage of up to 75% (w/w) neoteric solvent. Moreover, this reaction medium was used to perform a chemoenzymatic cascade toward biaryl amines by coupling a Suzuki reaction sequentially with an enantioselective bioamination catalyzed by the recently discovered ATA from Exophiala xenobiotica (EX-wTA). The solubilizing properties of DESs enabled the metal catalyzed step at 200 mM loading of substrate and the subsequent biotransformation at 25 mM.

Analogues of the natural product collismycin bearing a carboxylic acid moiety has been efficiently synthesised from several collismycin precursors through a laccase-catalysed oxidation under mild conditions with TEMPO (2,2,6,6-tetramethylpiperidin-1-oxyl) as a mediator and aerial O2 as an oxidant in aqueous medium. The biotransformations proceeded with excellent yields (85–95%) and involved, depending on the precursor, the oxidation of a benzylic hydroxyl group or the bioconversion of an aldoxime group into carboxylic acid. Since the latter is herein reported for the first time, we explored the potential of this novel oxime cleavage with several synthetic aldo- and ketoximes. Thus, the laccase/TEMPO system proved to be an efficient and green alternative for the deprotection of both aromatic and aliphatic ketoximes into the corresponding ketones. On the other hand, the reaction with aldoximes leads to dimeric species generated by coupling reactions.

One of the pioneering examples of chemoenzymatic cascades in water such as the palladium-catalysed Suzuki-cross coupling followed by an enzymatic reduction has been revisited by the employment of a medium containing Deep Eutectic Solvents (DESs) for the catalytic performance. Thus, the unique properties of these neoteric solvents enabled to reach high substrate concentration for the overall process. Moreover, both isolated enzymes and whole cells exhibited excellent activities which allowed to obtain a set of chiral biaryl alcohols in good yields and very high enantiomeric excess (> 99%).

A dual ruthenium/ketoreductase catalytic system has been developed for the conversion of β‐ketonitriles into optically active β‐hydroxyamides through an unprecedented hydration/bioreduction cascade process in aqueous medium working in concurrent mode. The ketoreductase‐mediated ketone reduction took place with exquisite stereoselectivity and it was simultaneous to the nitrile hydration promoted by the ruthenium catalyst. The overall transformation occurred: (i) employing commercially and readily available catalytic systems (ii) under mild reaction conditions, (iii) with high degree of conversion and excellent stereoselectivity, and (iv) without the need to isolate intermediates and with high final product yields. This genuine process demonstrates the benefits of combining metal and enzymatic catalysis to tackle the limitations arising from each field., We are indebted to the MINECO of Spain (CTQ2013‐40591‐P and CTQ2016‐75986‐P) and the Gobierno del Principado de Asturias (Project GRUPIN14‐006) for financial support. E. Liardo acknowledges funding from the European Union's Horizon 2020 MSCA ITN‐EID program (grant agreement No 634200). The authors also thank Dr. Martin Schürmann (InnoSyn) and Prof. Harald Gröger (Bielefeld University) for the generous gift of the KRED of Rhodococcus ruber and Lactobacillus kefir, respectively.

E. Liardo acknowledges funding from the European Union's Horizon 2020 MSCA ITN‐EID program under grant agreement no. 634200 (Project BIOCASCADES). Authors from the University of Oviedo thank the Ministerio de Ciencia e Innovación of Spain (Project CTQ 2014‐55015) and Principado de Asturias (FC‐15‐GRUPIN‐14‐002) for financial support.

The first application of Deep Eutectic Solvents (DESs) in the asymmetric bioreduction of ketones has been accomplished for purified ketoreductases (KREDs). The performance of the biocatalysts was enhanced by increasing the percentage of neoteric solvent in DES-buffer mixtures. At a buffer content of 50% (w/w) and even 20% (w/w), the combination of either choline chloride (ChCl)/glycerol (Gly) (1 : 2) or ChCl/sorbitol (1 : 1) proved to be most effective for achieving up to >99% conversion and up to >99% enantiomeric excess of the corresponding secondary alcohols. Moreover, this reaction medium was used to perform the first example of a chemoenzymatic cascade process in DES-buffer mixtures, namely the ruthenium-catalysed isomerisation of racemic allylic alcohols coupled with a further enantioselective bioreduction, in both sequential and concurrent modes.

Argimycins P are a recently identified family of polyketide alkaloids encoded by the cryptic gene cluster arp of Streptomyces argillaceus. These compounds contain either a piperideine ring, or a piperidine ring which may be fused to a five membered ring, and a polyene side chain, which is bound in some cases to an N-acetylcysteine moiety. The arp cluster consists of 11 genes coding for structural proteins, two for regulatory proteins and one for a hypothetical protein. Herein, we have characterized the post-piperideine ring biosynthesis steps of argimycins P through the generation of mutants in arp genes, the identification and characterization of compounds accumulated by those mutants, and cross-feeding experiments between mutants. Based in these results, a biosynthesis pathway is proposed assigning roles to every arp gene product. The regulation of the arp cluster is also addressed by inactivating/overexpressing the positive SARP-like arpRI and the negative TetR-like arpRII transcriptional regulators and determining the effect on argimycins P production, and through gene expression analyses (reverse transcription PCR and quantitative real-time PCR) of arp genes in regulatory mutants in comparison to the wild type strain. These findings will contribute to deepen the knowledge on the biosynthesis of piperidine-containing polyketides and provide tools that can be used to generate new analogs by genetic engineering and/or biocatalysis.

This chapter discusses the development that EntreChem has brought over the last decade, with emphasis on biocatalysis and the use in asymmetric synthesis of lipases, oxidoreductases, transaminases and laccases, as well as with initiatives in synthetic biology and in the natural products field. Subsequently, critical considerations on how biocatalysis can benefit from the business–research interface are provided. To illustrate the challenges, comparison with the drug development field are made, and constructive suggestions given.

The development of cell-free and self-sufficient biocatalytic systems represents an emerging approach to address more complex synthetic schemes under nonphysiological conditions. Herein, we report the development of a self-sufficient heterogeneous biocatalyst for the synthesis of chiral alcohols without the need to add an exogenous cofactor. In this work, an NADPH-dependent ketoreductase was primarily stabilized and further co-immobilized with NADPH to catalyze asymmetric reductions without the addition of an exogenous cofactor. As a result, the immobilized cofactor is accessible, and thus, it is recycled inside the porous structure without diffusing out into the bulk, as demonstrated by single-particle in operando studies. This self-sufficient heterogeneous biocatalyst was used and recycled for the asymmetric reduction of eleven carbonyl compounds in a batch reactor without the addition of exogenous NADPH to achieve the corresponding alcohols in 100 % yield and >99 % ee; this high performance was maintained over five consecutive reaction cycles. Likewise, the self-sufficient heterogeneous biocatalyst was integrated into a plug flow reactor for the continuous synthesis of one model secondary alcohol, which gave rise to a space-time yield of 97-112 g L-1 day-1 ; additionally, the immobilized cofactor accumulated a total turnover number of 1076 for 120 h. This is one of the few examples of the successful implementation of continuous reactions in aqueous media catalyzed by cell-free and immobilized systems that integrate both enzymes and cofactors into the solid phase.

Chemoenzymatic syntheses of both enantiomers of cis- and trans-2-aminocyclopentanol as well as cis- and trans-2-aminocyclohexanol, which are valuable building blocks for a plethora of ligands and pharmaceuticals have been efficiently carried out. The strategy involves the stereospecific syntheses of racemic aminocycloalkanol precursors via tagging of a phthalimide as a masking group and subsequent lipase-catalyzed kinetic resolution. Most of the lipases exhibited excellent enantioselectivity (E ≫ 200) in the transesterification reactions of trans-derivatives, with both N-protected (R,R)-amino acetates and (S,S)-amino alcohols being isolated in enantiopure form. With regard to cis-derivatives, lipases were also very selective, even though the biotransformations were significantly slower.

Summary Collismycin A is a member of the 2,2′-bipyridyl family of natural products that shows cytotoxic activity. Structurally, it belongs to the hybrid polyketides-nonribosomal peptides. After the isolation and characterization of the collismycin A gene cluster, we have used the combination of two different approaches (insertional inactivation and biocatalysis) to increase structural diversity in this natural product class. Twelve collismycin analogs were generated with modifications in the second pyridine ring of collismycin A, thus potentially maintaining biologic activity. None of these analogs showed better cytotoxic activity than the parental collismycin. However, some analogs showed neuroprotective activity and one of them (collismycin H) showed better values for neuroprotection against oxidative stress in a zebrafish model than those of collismycin A. Interestingly, this analog also showed very poor cytotoxic activity, a feature very desirable for a neuroprotectant compound.

A hybrid organo- and biocatalytic system for the asymmetric conversion of racemic alcohols into amines was developed. Combining an organocatalyst, AZADO, an oxidant, NaOCl, and an enzyme, ω-transaminase, we implemented a one-pot oxidation–transamination sequential process in aqueous medium. The method showed broad substrate scope and was successfully applied to conventional secondary alcohols and sterically hindered β-substituted cycloalkanols, where a highly stereoselective dynamic asymmetric bioamination enabled us to set up both contiguous stereocenters with very high enantio- and diastereomeric ratio (>90% yield, >99% ee, and up to 49:1 dr).

The ruthenium-catalyzed redox isomerization of allylic alcohols was successfully coupled with the enantioselective enzymatic ketone reduction (mediated by KREDs) in a concurrent process in aqueous medium. The overall transformation, formally the asymmetric reduction of allylic alcohols, took place with excellent conversions and enantioselectivities, under mild reaction conditions, employing commercially and readily available catalytic systems, and without external coenzymes or cofactors. Optimization resulted in a multistep approach and a genuine cascade reaction where the metal catalyst and biocatalyst coexist from the beginning.

Several acyl derivatives of the aureolic acid chromomycin A(3) were obtained via lipase-catalyzed acylation. Lipase B from Candida antarctica (CAL-B) was found to be the only active biocatalyst, directing the acylation regioselectively towards the terminal secondary hydroxyl group of the aglycone side chain. All new chromomycin A(3) derivatives showed antitumor activity at the micromolar or lower level concentration. Particularly, chromomycin A(3) 4'-vinyladipate showed 3-5 times higher activity against the four tumor cell lines assayed as compared to chromomycin A(3).

A variety of aureolic acids was efficiently obtained by lipase-catalyzed regioselective acylation reactions of mithramycin and its analogues mithramycin SK and mithramycin SDK. The acylation took place in the aglycone moiety or in the B sugar unit, depending on the substrate, lipase and acyl donor considered. Most of the novel acylated derivatives showed antitumor activity at double digit nanomolar concentrations, in some cases significantly improving the activity of the parent drugs.

Mithramycin and chromomycin A(3) are two structurally related antitumour compounds, which differ in the glycosylation profiles and functional group substitutions of the sugars. Chromomycin contains two acetyl groups, which are incorporated during the biosynthesis by the acetyltransferase CmmA in Streptomyces griseus ssp. griseus. A bioconversion strategy using an engineered S. griseus strain generated seven novel acetylated mithramycins. The newly formed compounds were purified and characterized by MS and NMR. These new compounds differ from their parental compounds in the presence of one, two or three acetyl groups, attached at 3E, 4E and/or 4D positions. All new mithramycin analogues showed antitumour activity at micromolar of lower concentrations. Some of the compounds showed improved activities against glioblastoma or pancreas tumour cells. The CmmA acetyltransferase was located in the cell membrane and was shown to accept several acyl-CoA substrates. All these results highlight the potential of CmmA as a tool to create structural diversity in these antitumour compounds.

Optically active trans - N -Boc-cyclopentane- and cyclohexane-1,2-diamines ( 7 ) were prepared by a chemoenzymatic method from the corresponding (±)- trans - N , N -diallylcycloalkane-1,2-diamine. These mono-carbamates 7 (ee=99%) were used as the starting materials in the syntheses of different vicinal primary–tertiary diamines. Thus, by means of a simple three-step sequence involving a reductive-amination of an aromatic aldehyde with 7 , N-methylation and finally, cleavage of the Boc group, several trans - N -(arylmethyl)- N -methylcyclopentane- and cyclohexane-1,2-diamines were obtained in high yields.

A novel and efficient chemoenzymatic protocol for the preparation of both enantiomers of trans -2-aminocyclopentanol is described. The key steps of this strategy are the synthesis and subsequent Burkholderia cepacia lipase-catalyzed resolution of the racemic precursor trans -2-(diallylamino)cyclopentanol. In addition, a variety of diversely substituted derivatives are prepared from the enantiopure compounds isolated in the biotransformation by means of simple protection–deprotection reactions.

Syntheses and lipase-catalyzed resolutions of a trans -2-aminocyclopentanol rac - 2 and trans -cyclopentane-1,2-diamine rac - 3 , bearers of an anthracene unit, have been effectively carried out. Burkholderia cepacia lipase catalyzed the transesterification of the β-amino alcohol with very high enantioselectivity ( E > 200). Lipase B from Candida antarctica showed moderate enantioselectivity in the acetylation of the diamine when 1-phenylethyl acetate was used as an acyl donor. In addition, the treatment of the optically active diamine (1 S ,2 S )- 3 (ee = 95%) with pyridine-2,6-dicarbonyl dichloride yielded the bis(aminoamide) 6 , which was tested as a chiral solvating agent (CSA) of carboxylic acids.

A family of pincer-like receptors ( 2 – 5 ) has been synthesized and tested for the NMR enantiodiscrimination (CSA) of chiral carboxylic acids. Starting from a previous design ( 1 ), different structural variables have been mapped on the receptor frame. The splitting of the signals of the acids upon the addition of the CSAs largely depends on these structural variables. Thus, we concluded that the C 2 symmetrical pyridine-2,6-biscarboxamide moiety is a key structural feature for the efficiency of the CSA. Structural studies by NMR and molecular modeling showed that this moiety promotes the U-shape-folded pincer-like conformation by intramolecular H-bonds. On the other hand, we also observed that the cyclohexane-1,2-diamine derivative 5 is a more versatile CSA than its cyclopentane analogue 1 , as 5 shows a better performance for more structurally different acids. However, the original cyclopentane derivative ( 1 ) remained the best for the arylpropionic acids. Finally, combination of NMR and modeling studies allowed us to propose a reasonable model for the interaction and, accordingly, for the observed NMR enantiodiscrimination.

An improved chemoenzymatic protocol for the synthesis of both enantiomers of trans -cyclopentane-1,2-diamine is described. The key part of the strategy relies on the synthesis and subsequent enzymatic resolution of its racemic precursor trans - N , N -diallylcyclopentane-1,2-diamine in which the primary amino group is masked as a tertiary diallylamine. Lipase B from Candida antarctica (CAL-B) catalyzes the N-acylation of this diamine with excellent enantioselectivity ( E >200). Further deallylation and derivatization of the enantioenriched compounds (ee ⩾ 97%) obtained in the biotransformation gave access to diversely substituted derivatives.