Synthetic Capability Research Articles

Reductive alkyl-alkyl coupling from isolable nickel-alkyl complexes.

The selective cross-coupling of two alkyl electrophiles to construct complex molecules remains a challenge in organic synthesis1,2. Known reactions are optimized for specific electrophiles and are not amenable to interchangeably varying electrophilic substrates that are sourced from common alkyl building blocks, such as amines, carboxylic acids and halides3-5. These limitations restrict the types of alkyl substrate that can be modified and, ultimately, the chemical space that can be explored6. Here we report a general solution to these limitations that enables a combinatorial approach to alkyl-alkyl cross-coupling reactions. This methodology relies on the discovery of unusually persistent Ni(alkyl) complexes that can be formed directly by oxidative addition of alkyl halides, redox-active esters or pyridinium salts. The resulting alkyl complexes can be isolated or directly telescoped to couple with a second alkyl electrophile, which represent cross-selective reactions that were previously unknown. The utility of this synthetic capability is showcased in the rapid diversification of amino acids, natural products, pharmaceuticals and drug-like building blocks by various combinations of dehalogenative, decarboxylative or deaminative coupling. In addition to a robust scope, this work provides insights into the organometallic chemistry of synthetically relevant Ni(alkyl) complexes through crystallographic analysis, stereochemical probes and spectroscopic studies.

Enhancement of thermostability and expression level of Rasamsonia emersonii lipase in Pichia pastoris and its application in biodiesel production in a continuous flow reactor

The acidic lipase from Rasamsonia emersonii named LIPR has great potential for biodiesel synthesis due to its strong methanol tolerance. Nonetheless, the limited thermostability of LIPR and low expression level in Escherichia coli remain major obstacles to its use in biodiesel synthesis. To enhance the thermostability, the mutant LIPR harboring mutations A126C-P238C for the formation of a new disulfide bond and amino acid substitution D214L was obtained through rational design. To our delight, the thermostability of LIPR mutant was greatly improved. Moreover, a comprehensive optimization strategy, such as employing the Mss signal peptide, co-expressing the molecular chaperone protein disulfide isomerase (PDI), knocking out the vacuolar sorting receptor gene VPS10-01, and overexpressing the dihydroxyacetone synthase gene DAS2, was adopted to obtain the combination-optimized mutant Pichia pastoris strain GS54. Furthermore, the biodiesel synthetic capability with the mutant GS54-LIPR was verified and the production yield was 52.2 % after 24 h in a shake flask. Subsequently, a continuous flow system was adopted to increase the biodiesel yield to 73.6 % within 3 h, demonstrating its efficacy in enhancing enzyme biocatalysis. The engineered GS54-LIPR mutant lipase is an efficient and reusable biocatalyst for the sustained production of biodiesel in a continuous flow reaction.

Pd and Pt Complexes of Benzo-Fused Dipyrrins: Synthesis, Structure, Electrochemical, and Optical Properties.

Benzo-fused dipyrrins are π-extended analogs of conventional dipyrrins, which exhibit bathochromically shifted absorption and possess the synthetic capability to bind various metal ions. We aimed to investigate the synthetic potential of benzo-fused dipyrrins in the complexation with transition metals. Two new complexes with Pd2+ and Pt2+ were synthesized and characterized. X-ray crystallography reveals that both complexes exhibit a zigzag geometry with square planar coordination of the central metal. The Pd2+ complex possesses a very weak fluorescence at 665 nm, while the Pt2+ complex is completely nonemissive. Transient absorption spectroscopy confirmed triplet excited state formation for both complexes; however, they are short-lived and no phosphorescence was observed even at 77K. DFT calculations support the experimental observation, revealing the existence of the low-lying ligand-metal charge-transfer (LMCT) triplet state acting as an energy sink.

Mathematical and In Silico Analysis of Synthetic Inhibitory Circuits That Program Self-Organizing Multicellular Structures.

Bottom-up approaches are becoming increasingly popular for studying multicellular self-organization and development. In contrast to the classic top-down approach, where parts of the organization/developmental process are broken to understand the process, the goal is to build the process to understand it. For example, synthetic circuits have been built to understand how cell-cell communication and differential adhesion can drive multicellular development. The majority of current bottom-up efforts focus on using activatory circuits to engineer and understand development, but efforts with inhibitory circuits have been minimal. Yet, inhibitory circuits are ubiquitous and vital to native developmental processes. Thus, inhibitory circuits are a crucial yet poorly studied facet of bottom-up multicellular development. To demonstrate the potential of inhibitory circuits for building and developing multicellular structures, several synthetic inhibitory circuits that combine engineered cell-cell communication and differential adhesion were designed, and then examined for synthetic development capability using a previously validated in silico framework. These designed inhibitory circuits can build a variety of patterned, self-organized structures and even morphological oscillations. These results support that inhibitory circuits can be powerful tools for building, studying, and understanding developmental processes.

Organophotocatalytic Remote Thiocyanation Reaction via Ring-Opening Functionalization of Cycloalkanols.

The remote C(sp3)-SCN bond formation via ring-opening functionalization of cycloalkanols with N-thiocyanatosaccharin as the precursor of SCN radicals and pyrylium salt as the organic photocatalyst under visible light has been developed. Thus, various terminal keto thiocyanates were prepared without transition metals and oxidants in moderate to good yields. The simplicity, wide substrate scope and mild conditions feature its synthetic application capability.

Metal-Free Synthesis of Functionalized Quinolines from 2-Styrylanilines and 2-Methylbenzothiazoles/2-Methylquinolines.

A facile functionalization of C(sp3)-H bonds and tandem cyclization strategy to synthesize quinoline derivatives from 2-methylbenzothiazoles or 2-methylquinolines and 2-styrylanilines has been developed. This work avoids the requirement for transition metals, offering a mild approach to activation of C(sp3)-H bonds and formation of new C-C and C-N bonds. This strategy features excellent functional group tolerance and scaled-up synthetic capability, thus providing an efficient and environmentally friendly access to medicinally valuable quinolines.

Hybrid Control Scheme for VSC Presenting Both Grid-Forming and Grid-Following Capabilities

This work proposes the Hybrid Control Converter (HCC), a new kind of VSC control. This method aims to have one single converter mimic the behavior of two individual, virtual converters working in parallel (one with grid-following and the other with grid-forming control). This way, the hybrid converter can show behavioral characteristics of both kinds of converter control at the same time. Two possible applications for the HCC are presented. The first one is related to synthetic inertia capability of wind turbines. Results show that the HCC presents superior performance when compared to conventional techniques based on grid following converters, resulting in a smaller grid frequency drop during transients. The second application shows that the HCC allows for autonomous connection of multiple distinct AC systems using a meshed DC transmission system. This enables automatic frequency support and generation and load sharing between the AC grids without requiring any specific action by the system operator.

Host’s demand for essential amino acids is compensated by an extracellular bacterial symbiont in a hemipteran insect model

Plant sap is a nutritionally unbalanced diet that constitutes a challenge for insects that feed exclusively on it. Sap-sucking hemipteran insects generally overcome this challenge by harboring beneficial microorganisms in their specialized symbiotic organ, either intracellularly or extracellularly. Genomic information of these bacterial symbionts suggests that their primary role is to supply essential amino acids, but empirical evidence has been virtually limited to the intracellular symbiosis between aphids and Buchnera. Here we investigated the amino acid complementation by the extracellular symbiotic bacterium Ishikawaella harbored in the midgut symbiotic organ of the stinkbug Megacopta punctatissima. We evaluated amino acid compositions of the phloem sap of plants on which the insect feeds, as well as those of its hemolymph, whole body hydrolysate, and excreta. The results highlighted that the essential amino acids in the diet are apparently insufficient for the stinkbug development. Experimental symbiont removal caused severe shortfalls of some essential amino acids, including branched-chain and aromatic amino acids. In vitro culturing of the isolated symbiotic organ demonstrated that hemolymph-circulating metabolites, glutamine and trehalose, efficiently fuel the production of essential amino acids. Branched-chain amino acids and aromatic amino acids are the ones preferentially synthesized despite the symbiont’s synthetic capability of all essential amino acids. These results indicate that the symbiont-mediated amino acid compensation is quantitatively optimized in the stinkbug-Ishikawaella gut symbiotic association as in the aphid-Buchnera intracellular symbiotic association. The convergence of symbiont functions across distinct nutritional symbiotic systems provides insight into how host-symbiont interactions have been shaped over evolutionary time.

Efficient synthesis of nigerose by a novel nigerose phosphorylase from Anaerosporobacter mobilis

Nigerose is a kind of rare disaccharide connected by an α-1,3 glucosidic bond, which is a potential probiotic due to its anti-digestive properties and beneficial functions. This study identified and characterized a novel GH65 glycoside phosphorylase derived from Anaerosporobacter mobilis (AmNP). This new protein could specifically catalyze the phospholysis of nigerose to generate glucose and glucose-1-phosphate in the presence of phosphate, indicating it was a typical nigerose phosphorylase. Compared to the previously reported nigerose phosphorylases, AmNP exhibited lower affinity towards nigerose in phosphorolysis reaction and higher affinity towards glucose in reverse phosphorolysis reaction, which indicated that AmNP might be superior in the synthetic capability of disaccharide. Then AmNP was employed to synergize with maltose phosphorylase from Lactobacillus brevis (LbMP) to catalyze the synthesis of nigerose using maltose as the substrate. After optimization of reaction conditions, the highest nigerose yield reached 132.0 g/L with a 66.3% conversion rate, which was higher than ever reported cases using the same reaction pathway to our knowledge. These findings on AmNP in this work were expected to provide a new candidate for large-scale enzymatic synthesis of nigerose and have important theoretical significance for studying nigerose phosphorylase.

Study of serum cholinesterase as a biomarker in a sample of patients with viral hepatitis B or hepatitis C in Baghdad

The most prevalent illnesses that affect the liver are viral infections; when the liver cell is destroyed by viruses, it loses its function and most of the body's processes are compromised. The liver is the primary source of serum cholinesterase. Therefore, serum cholinesterase can be used as a predictive biomarker for the liver's synthetic capability. This study aims to evaluate serum cholinesterase as a biomarker in patients with hepatitis B virus (HBV) or hepatitis C virus (HCV). The study was conducted at the Gastroenterology and Hepatology Teaching Hospital and Poisoning Consultation Center in Baghdad during the interval from November 2021 to March 2022. The liver function tests and serum cholinesterase were measured in one hundred fifty samples. Fifty patients with HBV and fifty patients with HCV were compared with fifty healthy individuals as a control group. The mean serum cholinesterase in the HBV and HCV patient groups (8528.76±2000.45 U/L and 7494.12± 2586.30 U/L, respectively) was lower than in the control group (9380.12±1848.96 U/L), and the difference was statistically significant (P < 0.05). The mean serum cholinesterase in the HCV patient group (7494.12±2586.30 U/L) was significantly lower (P < 0.05) than in the HBV patient group (8528.76 ±2000.45 U/L).

Thioester-Assisted Sortase-A-Mediated Ligation.

Sortase A (SrtA)-mediated ligation, a popular method for protein labeling and semi-synthesis, is limited by its reversibility and dependence on the LPxTG motif, where "x" is any amino acid. Here, we report that SrtA can mediate the efficient and irreversible ligation of a protein/peptide containing a C-terminal thioester with another protein/peptide bearing an N-terminal Gly, with broad tolerance for a wide variety of LPxT-derived sequences. This strategy, the thioester-assisted SrtA-mediated ligation, enabled the expedient preparation of proteins bearing various N- or C-terminal labels, including post-translationally modified proteins such as the Ser139-phosphorylated histone H2AX and Lys9-methylated histone H3, with less dependence on the LPxTG motif. Our study validates the chemical modification of substrates as an effective means of augmenting the synthetic capability of existing enzymatic methods.

Thioester‐Assisted Sortase‐A‐Mediated Ligation

AbstractSortase A (SrtA)‐mediated ligation, a popular method for protein labeling and semi‐synthesis, is limited by its reversibility and dependence on the LPxTG motif, where “x” is any amino acid. Here, we report that SrtA can mediate the efficient and irreversible ligation of a protein/peptide containing a C‐terminal thioester with another protein/peptide bearing an N‐terminal Gly, with broad tolerance for a wide variety of LPxT‐derived sequences. This strategy, the thioester‐assisted SrtA‐mediated ligation, enabled the expedient preparation of proteins bearing various N‐ or C‐terminal labels, including post‐translationally modified proteins such as the Ser139‐phosphorylated histone H2AX and Lys9‐methylated histone H3, with less dependence on the LPxTG motif. Our study validates the chemical modification of substrates as an effective means of augmenting the synthetic capability of existing enzymatic methods.

Engineering Prophylactic Biosynthesis of an Antituberculosis Antibiotic

Tuberculosis is a deadly respiratory disease caused by the bacterium Mycobacterium tuberculosis which does not currently have a fully effective vaccine. The goal of this project is to develop an effective prophylaxis for tuberculosis using mammalian cells to biosynthesize the anti‐tuberculosis antibiotic, d‐cycloserine (dCS). We took two approaches to activate this biosynthetic pathway in mammalian cells. Initially, Chinese Hamster Ovarian cancer cells (CHO) were transfected with plasmids encoding all six dCS biosynthesis enzymes (dcsA‐G) and isolated total protein was tested for synthetic capability. The expression of the genes detected by fluorescence microscopy was low and the in‐vitro dCS biosynthesis from lysates was not detected by HPLC. Currently, individual enzymes are being optimized, starting with dcsE, which converts L‐serine to O‐acetyl‐L‐serine. To focus on dcsE, human lung epithelial cancer cells (A549) were transfected with a higher concentration of DNA. High dcsE expression was detected by fluorescence microscopy and a Western Blot was used to detect the presence of our GFP tagged dcsE protein. The Western Blot indicated that GFP dimerized and there is no dcsE tagged with GFP.

The Unexpected Importance of the Primary Structure of the Hydrophobic Part of One-Component Ionizable Amphiphilic Janus Dendrimers in Targeted mRNA Delivery Activity.

Viral and synthetic vectors for delivery of nucleic acids impacted genetic nanomedicine by aiding the rapid development of the extraordinarily efficient Covid-19 vaccines. Access to targeted delivery of nucleic acids is expected to expand the field of nanomedicine beyond most expectations. Both viral and synthetic vectors have advantages and disadvantages. The major advantage of the synthetic vectors is their unlimited synthetic capability. The four-component lipid nanoparticles (LNPs) are the leading nonviral vector for mRNA used by Pfizer and Moderna in Covid-19 vaccines. Their synthetic capacity inspired us to develop a one-component multifunctional sequence-defined ionizable amphiphilic Janus dendrimer (IAJD) delivery system for mRNA. The first experiments on IAJDs provided, through a rational-library design combined with orthogonal-modular accelerated synthesis and sequence control in their hydrophilic part, some of the most active synthetic vectors for the delivery of mRNA to lung. The second experiments employed a similar strategy, generating, by a less complex hydrophilic structure, a library of IAJDs targeting spleen, liver, and lung. Here, we report preliminary studies designing the hydrophobic region of IAJDs by using dissimilar alkyl lengths and demonstrate the unexpectedly important role of the primary structure of the hydrophobic part of IAJDs by increasing up to 90.2-fold the activity of targeted delivery of mRNA to spleen, lymph nodes, liver, and lung. The principles of the design strategy reported here and in previous publications indicate that IAJDs could have a profound impact on the future of genetic nanomedicine.

Efficient Synthetic Access to Novel Indolo[2,3-b]Quinoxaline-based Heterocycles.

This paper showed the synthetic capability of the indolo[2,3-b]quinoxaline nucleus to be provided as an excellent precursor for the synthesis of various heterocyclic compounds. These synthetic routes proceed via the formation of 3-(6H-indolo[2,3-b]quinoxalin-6-yl) propane hydrazide (2). The carbohydrazide 2 and its reactions with different reagents give five and six-membered rings, such as 1,3,4-thiadiazole, 1,3,4- oxadiazole, 1,2,4-triazole, and 1,2,4-triazine. All chemicals used in the current study were of analytical grade. Melting points were determined using an APP Digital ST 15 melting point apparatus and were uncorrected. FT-IR spectra were recorded on a Pye- Unicam SP3-100 and Shimadzu-408 spectrophotometers in KBr pellets and given in (cm-1) KBr. The NMR spectra were detected by a Bruker AV-400 spectrometer (400 MHz for 1H, 100 MHz for 1C and 40.55 MHz for 15N), Institute of Organic Chemistry, Karlsruhe, Germany. Chemical shifts were expressed as δ (ppm) with TMS as an internal reference. Mass spectrometry was provided on a Varian MAT 312 instrument in EI mode (70 eV). The target compounds were obtained, and their structures were completely elucidated by various spectral and elemental analyses (Ft-IR, 1H-NMR, 13;C-NMR, and mass spectrometry). The current work showed a view of the reactivity of the carbohydrazide group. The carbohydrazide 2 was obtained from the hydrazinolysis of carboethoxy compound 1 and exploited as a key intermediate to synthesize heterocyclic compounds with different rings.

Chemical synthesis of 4'-thio and 4'-sulfinyl pyrimidine nucleoside analogues.

Analogues of the canonical nucleosides required for nucleic acid synthesis have a longstanding presence and proven capability within antiviral and anticancer research. 4'-Thionucleosides, that incorporate bioisosteric replacement of furanose oxygen with sulfur, represent an important chemotype within this field. Established herein is synthetic capability towards a common 4-thioribose building block that enables access to thio-ribo and thio-arabino pyrimidine nucleosides, alongside their 4'-sulfinyl derivatives. In addition, this building block methodology is templated to deliver 4'-thio and 4'-sulfinyl analogues of the established anticancer drug gemcitabine. Cytotoxic capability of these new analogues is evaluated against human pancreatic cancer and human primary glioblastoma cell lines, with observed activities ranging from low μM to >200 μM; explanation for this reduced activity, compared to established nucleoside analogues, is yet unclear. Access to these chemotypes, with thiohemiaminal linkages, will enable a wider exploration of purine and triphosphate analogues and the application of such materials for potential resistance towards relevant hydrolytic enzymes within nucleic acid biochemistries.

General Tolerance of Galactosyltransferases toward UDP‐galactosamine Expands Their Synthetic Capability

AbstractAccessing large numbers of structurally diverse glycans and derivatives is essential to functional glycomics. We showed a general tolerance of galactosyltransferases toward uridine‐diphosphate‐galactosamine (UDP‐GalN), which is not a commonly used sugar nucleotide donor. The property was harnessed to develop a two‐step chemoenzymatic strategy for facile synthesis of novel and divergent N‐acetylgalactosamine (GalNAc)‐glycosides and derivatives in preparative scales. The discovery and the application of the new property of existing glycosyltransferases expand their catalytic capabilities in generating novel carbohydrate linkages, thus prompting the synthesis of diverse glycans and glycoconjugates for biological studies.

General Tolerance of Galactosyltransferases toward UDP-galactosamine Expands Their Synthetic Capability.

Accessing large numbers of structurally diverse glycans and derivatives is essential to functional glycomics. We showed a general tolerance of galactosyltransferases toward uridine-diphosphate-galactosamine (UDP-GalN), which is not a commonly used sugar nucleotide donor. The property was harnessed to develop a two-step chemoenzymatic strategy for facile synthesis of novel and divergent N-acetylgalactosamine (GalNAc)-glycosides and derivatives in preparative scales. The discovery and the application of the new property of existing glycosyltransferases expand their catalytic capabilities in generating novel carbohydrate linkages, thus prompting the synthesis of diverse glycans and glycoconjugates for biological studies.

One-Dimensional Superlattice Heterostructure Library

Axially, epitaxially organizing nano-objects of distinct compositions and structures into superlattice nanowires enables full utilization of sunlight, readily engineered band structures, and tunable geometric parameters to fit carrier transport, thus holding great promise for optoelectronics and solar-to-fuel conversion. To maximize their efficiency, the general and high-precision synthesis of colloidal axial superlattice nanowires (ASLNWs) with programmable compositions and structures is the prerequisite; however, it remains challenging. Here, we report an axial encoding methodology toward the ASLNW library with precise control over their compositions, dimensions, crystal phases, interfaces, and periodicity. Using a predesigned, editable nanoparticle framework that offers the synthetic selectivity, we are able to chemically decouple adjacent sub-objects in ASLNWs and thus craft them in a controlled approach, yielding a library of distinct ASLNWs. We integrate therein plasmonic, metallic, or near-infrared-active chalcogenides, which hold great potential in solar energy conversion. Such synthetic capability enables a performance boost in target applications, as we report order-of-magnitude enhanced photocatalytic hydrogen production rates using optimized ASLNWs compared to corresponding solo objects. Furthermore, it is expected that such unique superlattice nanowires could bring out new phenomena.

A strategic Ser/Cys exchange in the catalytic triad unlocks an acyltransferase-mediated synthesis of thioesters and tertiary amides

Expanding the toolbox of enzymatic reactions accessible to organic chemists is one of the major goals in biocatalysis. Here we describe the development of an acyltransferase variant from Mycobacterium smegmatis in which a strategic Ser/Cys exchange in the catalytic triad dramatically expanded its synthetic capability to yield a biocatalyst able to efficiently catalyse the formation of thioesters and tertiary amides in water. Preparative scale (250 mM) biotransformations were performed starting from different thiols and secondary amines with excellent yields and reactions times, using vinyl esters as acylating agents. The high substrate-to-catalyst ratio and the cofactor independence make this process a sustainable and cost-effective procedure that was successfully applied to the synthesis of acetyl coenzyme A as well as structurally simpler analogues. Computational studies provided insights into the enzymatic selectivity and substrate recognition. Preparative methods for thioester and tertiary amide formation are currently missing in the biocatalysis repertoire. Now, a mutation of serine to cysteine in the catalytic triad of an acyltransferase expands its synthetic capability to generate these compounds while retaining its natural activity towards alcohols.