6-Alkylsalicylic Acids and 6-Alkylresorcylic Acids from Ants in the Genus <Emphasis Type="Italic">Crematogaster</Emphasis> from Brunei

The defensive chemistry of two species of ants from Brunei in the genus Crematogaster (Physocrema group) has been investigated. Ants in this group release a white secretion from hypertrophied metapleural glands on their thorax when they are disturbed. Previously, one species in this group has been shown to produce alkylphenols and alkylresorcinols. In the present investigation, similar compounds along with salicylic acids and resorcylic acids that are anacardic acid and olivetolic acid homologs, respectively, are described from two species. The structures of these compounds were suggested by their spectroscopic data and confirmed by direct comparison with synthetic samples. Some of these compounds occur in lichens and have well documented physiological activities.     

Hydrophobicity‐enhanced adhesion of novel biomimetic biocompatible polyaspartamide derivative glues

The development of wet bioadhesives for tissue fixation and wound care remains a challenge. While various commercial bioadhesive products based on both natural and synthetic materials are available, both types of adhesive have several drawbacks including weak adhesion or toxicity. In this study, we present a novel mussel‐inspired synthetic adhesive based on polyaspartamide derivatives modified with dopamine and a series of hydrophobic n‐alkylamines (lauryl, octyl, hexyl and butyl), which shows very strong adhesion toward various types of substrates such as paper, glass and metals as well as several common plastics (0.1–0.6 MPa). Additionally, the effect of adding metal ions (Mg²⁺, Ca²⁺) as a coordination crosslinker to enhance adhesion performance was investigated using acryl plastic substrate. Even under deionized water conditions, the strong adhesion was found to be maintained for an appreciably long time after 24 h. This novel and biocompatible polymer glue system has potential in various applications including as a medical tissue adhesive and sealant. © 2018 Society of Chemical Industry     

Enantiocomplementary Michael Additions of Acetaldehyde to Aliphatic Nitroalkenes Catalyzed by Proline-Based Carboligases

The blockbuster drug Pregabalin is widely prescribed for the treatment of painful diabetic neuropathy. Given the continuous epidemic growth of diabetes, the development of sustainable synthesis routes for Pregabalin and structurally related pharmaceutically active γ-aminobutyric acid (GABA) derivatives is of high interest. Enantioenriched γ-nitroaldehydes are versatile synthons for the production of GABA derivatives, which can be prepared through a Michael-type addition of acetaldehyde to α,β-unsaturated nitroalkenes. Here we report that tailored variants of the promiscuous enzyme 4-oxalocrotonate tautomerase (4-OT) can accept diverse aliphatic α,β-unsaturated nitroalkenes as substrates for acetaldehyde addition. Highly enantioenriched aliphatic (R)- and (S)-γ-nitroaldehydes were obtained in good yields using two enantiocomplementary 4-OT variants. Our results underscore the synthetic potential of 4-OT for the preparation of structurally diverse synthons for bioactive analogues of Pregabalin.     

Nitrilase Activity Screening on Structurally Diverse Substrates: Providing Biocatalytic Tools for Organic Synthesis

A high‐throughput screening of candidate nitrilases against 25 structurally diverse substrates allowed us to create a wide collection of 125 experimentally validated nitrilases. The enzymes were selected by genomic approach from 700 diverse prokaryotic species and one metagenome as representative of the nitrilase family diversity. The enzymatic screening of this collection expands the biocatalytic toolbox for chemical synthesis by providing a large number of tested nitrilases with their assigned substrates. Three examples illustrate the synthetic potential of our enzyme collection. The syntheses of carboxylic acid building blocks, a β‐substituted phenylpropanoic acid, a cyclic γ‐keto carboxylic acid and a mononitrile monocarboxylic acid, were achieved from the corresponding nitrile substrates, using three new nitrilases (two from Sphingomonas wittichii and one from Syntrophobacter fumaroxidans). Improvements of nitrilase activities through the optimization of reaction parameters and the preparative biocatalytic synthesis are presented for these three examples.     

Hydrolysis of Acyl-Homogeneous and Fish Oil Triacylglycerols Using Desalted Midgut Extract from Atlantic Salmon, <Emphasis Type="Italic">Salmo salar</Emphasis>

Despite several studies aimed at evaluating the positional and fatty acid specificity of fish triacylglycerol (TAG) digestive lipases, there is still much uncertainty regarding these issues. The aim of the present study was therefore to address these questions in Atlantic salmon (Salmo salar L.). Crude luminal midgut extracts were collected from fed salmon and the hydrolysis studied for various substrates including triolein (Tri-18:1), trilinolein (Tri-18:2), trilinolenin (Tri-18:3), trieicosapentaenoin (Tri-20:5), tridocosahexaenoin (Tri-22:6) and natural fish oil TAG. Using Tri-18:1, in a time-curve model showed an initial high degree of sn-1 or sn-3 specificity where sn-1,2(2,3)-diacylglycerol (1,2(2,3)-DAG) and free fatty acid (FFA) were the main hydrolytic products up to 15 min. Lack of initial sn-2 specificity was confirmed by negligible sn-1,3-diacylglycerol (1,3-DAG) being produced. During the further hydrolysis of DAG, all positions appeared susceptible to attack causing a concomitantly small increase in sn-1(3)-monoacylglycerol (1(3)-MAG) and 2-MAG, but not at the level expected for an exclusively sn-1,3-specific lipase. Oleic acid (18:1n-9) and eicosapentaenoic acid (20:5n-3) were preferred substrates for hydrolysis using both fish oil and acyl-homogeneous TAGs with FFA as the main product of lipolysis. Hydrolysis of the natural fish oil TAG appeared slower yet produced proportionally more MAG and DAG after 5 min, and similar specificities, as for synthetic TAG substrates, were exhibited with 18:1n-9 and 20:5n-3 accumulating in the FFA fraction after 30 min. Notably, 16:0 was particularly conserved in MAG. As TAG resynthesis of absorbed lipid in salmon enterocytes proceeds preferably with 2-MAG as templates, the absorption of 2-MAG, produced during initial stages of TAG hydrolysis, would need to occur rapidly to be effectively utilised via the MAG pathway.     

Synthesis of novel amino(alkylamino)deoxychitins and the adsorption behavior of acid dye onto the resulting polymers

Novel chitin‐based materials were synthesized and the adsorption behavior of typical acid dyes to the resulting polymers has been evaluated. The successful synthetic reaction was confirmed by the infrared spectroscopic measurements. By the reaction of alkalichitin with tosyl chloride, the corresponding tosylchitin was synthesized as a soluble and reactive precursor. Next, aminodeoxychitin was synthesized by the reaction of the tosylchitin with ammonia. Similarly, 2′‐aminoethylamino‐ and 6′‐aminohexylaminodeoxychitins were synthesized by reacting the tosylchitin with ethylenediamine and hexamethylenediamine, respectively. It has been confirmed that the adsorption abilities of these polymers for acid dyes were significantly high, and also that one of the aminodeoxychitins showed a high adsorption ability for Cu²⁺ ion. On the basis of the adsorption data of acid dye on the aminodeoxychitin, the tosylchitin and the original chitin, the amino group contents at C₆ and C₂ positions were estimated. The aminodeoxychitin and aminoalkylaminodeoxychitins could be applicable to the adsorbent for anionic dyes and Cu²⁺ ion along with a precursor for further novel derivatives. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Practical Synthesis of Polysubstituted Imidazoles via Iodine‐ Catalyzed Aerobic Oxidative Cyclization of Aryl Ketones and Benzylamines

A practical synthetic method for polysubstituted imidazoles via iodine‐catalyzed aerobic oxidative cyclization of aryl ketones and benzylamines has been developed. It was found to tolerate a broad range of substrates to prepare polysubstituted imidazole derivatives in a one‐pot manner, and thus importantly allowed product diversity for imidazole chemistry. Additionally, the resultant 1,2,4‐trisubstituted imidazoles could be conveniently transformed to functionalized 1,2,4,5‐tetrasubstituted imidazoles via electrophilic substitution or direct C H functionalization, or 2,4‐diaryl‐1H‐imidazoles by debenzylation reaction, which further indicates potential applications of this method in synthetic and pharmaceutical chemistry.     

A parallel synthesis scheme for generating libraries of DNA polymerase substrates and inhibitors

We report a combinatorial approach aimed at producing in a single step a large family of nucleoside triphosphate derivatives that could be tested for their ability to be substrates for DNA polymerases. We propose as a unique triphosphate building block a nucleotide with a hydrazine function anchored to an imidazole ring. Condensation between the 5'-triphosphate derivative of 1-(2-deoxy-beta-D-erythro-pentofuranosyl)-imidazole-4-hydrazide (dY(NH(2))TP) and any aldehyde or ketone, followed by reduction of the intermediate hydrazones dXmTP, resulted in the corresponding hydrazides (dXnTP). Following this scheme, a series of aldehydes having various aromatic parts yielded a number of adducts dY(NHR)TP. Vent (exo-) DNA polymerase is found to be able to catalyse the single incorporation of these bulky triphosphate derivatives. Subsequent extensions of the modified pairs with canonical triphosphates resulted mainly in abortive elongations at primer+2, except after the incorporation of dY(NHben)TP and, to a lesser extent, dY(NHphe)TP opposite C. These results illustrate the potential of this parallel synthetic scheme for generating new substrates or inhibitors of replication in a single step.     

A General Approach to the Synthesis of β2‐Amino Acid Derivatives via Highly Efficient Catalytic Asymmetric Hydrogenation of α‐Aminomethylacrylates

A new strategy was developed for the synthesis of a valuable class of α‐aminomethylacrylates via the Baylis–Hillman reaction of different aldehydes with methyl acrylate followed by acetylation of the resulting allylic alcohols and S_N2′‐type amination of the allylic acetates. Asymmetric hydrogenation of these diverse olefinic precursors using rhodium(Et‐Duphos) catalysts provided the corresponding β²‐amino acid derivatives with excellent enantioselectivities and exceedingly high reactivities (up to >99.5% ee and S/C=10,000). The first hydrogenation of (Z)‐configurated substrates was studied for the synthesis of β²‐amino acid derivatives. The high influence of the substrate geometry and steric hindrance on the reactivity and enantioselectivity was also disclosed for this reaction. This protocol provides a highly practical, facile and scalable method for the preparation of optically pure β²‐amino acids and their derivatives under mild reaction conditions.     

Library Construction and Biological Evaluation of Enmein‐Type Diterpenoid Analogues as Potential Anticancer Agents

A library of promising enmein‐type 14‐O‐diterpenoid derivatives was constructed from a commercially available kaurene‐type oridonin by practical and efficient synthetic methods. These synthetic derivatives were evaluated for their antiproliferative activities against a set of four human cancer cell lines. The IC₅₀ values are similar to or improved over those of the parent molecule and paclitaxel, the latter of which was used as a positive control. Compound 29 was further investigated for its apoptotic properties against human hepatocarcinoma Bel‐7402 cells to better understand its mode of action. Moreover, compound 29 was shown to have potent antitumor activity in vivo in studies with a murine model of gastric cancer (MGC‐803 mice). These results warrant further preclinical investigations of these diterpenoid‐based analogues as potential novel anticancer chemotherapeutics.     

Evaluating the Catalytic Potential of a General RNA-Cleaving FANA Enzyme

The discovery of synthetic genetic polymers (XNAs) with catalytic activity demonstrates that natural genetic polymers are not unique in their ability to function as enzymes. However, all known examples of in vitro selected XNA enzymes function with lower activity than their natural counterparts, suggesting that XNAs might be limited in their ability to fold into structures with high catalytic activity. To explore this problem, we evaluated the catalytic potential of FANAzyme 12–7, an RNA-cleaving catalyst composed entirely of 2′-fluoroarabino nucleic acid (FANA) that was evolved to cleave RNA at a specific phosphodiester bond located between an unpaired guanine and a paired uracil in the substrate recognition arm. Here, we show that this activity extends to chimeric DNA substrates that contain a central riboguanosine (riboG) residue at the cleavage site. Surprisingly, FANAzyme 12–7 rivals known DNAzymes that were previously evolved to cleave chimeric DNA substrates under physiological conditions. These data provide convincing evidence that FANAzyme 12–7 maintains the catalytic potential of equivalent DNAzymes, which has important implications for the evolution of XNA catalysts and their contributions to future applications in synthetic biology.     

Quantitative Standards of 4-O-Acetyl- and 9-O-Acetyl-N-Acetylneuraminic Acid for the Analysis of Plasma and Serum

N-Acetylneuraminic acid (sialic acid, Neu5Ac) is one of a large, diverse family of nine-carbon monosaccharides that play roles in many biological functions such as immune response. Neu5Ac has previously been identified as a potential biomarker for the presence and pathogenesis of cardiovascular disease (CVD), diabetes and cancer. More recent research has highlighted acetylated sialic acid derivatives, specifically Neu5,9Ac₂, as biomarkers for oral and breast cancers, but advances in analysis have been hampered due to a lack of commercially available quantitative standards. We report here the synthesis of 9-O- and 4-O-acetylated sialic acids (Neu5,9Ac₂ and Neu4,5Ac₂) with optimisation of previously reported synthetic routes. Neu5,9Ac₂ was synthesised in 1 step in 68 % yield. Neu4,5Ac₂ was synthesised in 4 steps in 39 % overall yield. Synthesis was followed by analysis of these standards via quantitative NMR (qNMR) spectroscopy. Their utilisation for the identification and quantification of specific acetylated sialic acid derivatives in biological samples is also demonstrated.     

用合成腐植酸模型研究腐植酸中铜(Ⅱ)的吸附行为

在碱性条件下,以对苯醌、对苯二酚和4-氨基苯甲酸3种物质为前体,通过氧化聚合反应可以得到类似腐植酸性质的聚合物。用天然及合成腐植酸样品研究腐植酸对Cu2+的吸附作用。通过Langmuir和Freundlich等温吸附方程式来建立数学模型,进而计算出最大吸附强度K′(Langmuir)、最大吸附容量b(Langmuir)和吸附剂最大吸附容量m(Freundlich)。基于溶解度的研究,我们选择在pH3下进行吸附试验研究。在Langmuir吸附等温式中,RL(平衡参数)表示Cu2+的吸收情况。试验表明,在适当范围内,Cu2+呈现出良好的吸附效果。     

Biocatalytic Synthesis of Nitriles through Dehydration of Aldoximes: The Substrate Scope of Aldoxime Dehydratases

Nitriles, which are mostly needed and produced by the chemical industry, play a major role in various industry segments, ranging from high‐volume, low‐price sectors, such as polymers, to low‐volume, high‐price sectors, such as chiral pharma drugs. A common industrial technology for nitrile production is ammoxidation as a gas‐phase reaction at high temperature. Further popular approaches are substitution or addition reactions with hydrogen cyanide or derivatives thereof. A major drawback, however, is the very high toxicity of cyanide. Recently, as a synthetic alternative, a novel enzymatic approach towards nitriles has been developed with aldoxime dehydratases, which are capable of converting an aldoxime in one step through dehydration into nitriles. Because the aldoxime substrates are easily accessible, this route is of high interest for synthetic purposes. However, whenever a novel method is developed for organic synthesis, it raises the question of substrate scope as one of the key criteria for application as a “synthetic platform technology”. Thus, the scope of this review is to give an overview of the current state of the substrate scope of this enzymatic method for synthesizing nitriles with aldoxime dehydratases. As a recently emerging enzyme class, a range of substrates has already been studied so far, comprising nonchiral and chiral aldoximes. This enzyme class of aldoxime dehydratases shows a broad substrate tolerance and accepts aliphatic and aromatic aldoximes, as well as arylaliphatic aldoximes. Furthermore, aldoximes with a stereogenic center are also recognized and high enantioselectivities are found for 2‐arylpropylaldoximes, in particular. It is further noteworthy that the enantiopreference depends on the E and Z isomers. Thus, opposite enantiomers are accessible from the same racemic aldehyde and the same enzyme.     

Industrial utilization of C21 dicarboxylic acid

Interest in polyfunctional materials has increased steadily in recent years as polymer systems have become more prevalent in our society. One of the more unique and versatile of these products has only recently become commercially available, 5(6)-carboxy-4-hexyl-2-cyclohexene-1-octanoic acid. This C₂₁ dicarboxylic acid not only has the expected ability to be incorporated into polymers for modification of the system, but it also has very unique surfactant properties. The sodium, potassium, and ammonium salts of this C₂₁ dicarboxylic acid are unusually soluble in water, and the water solutions maintain relatively low viscosities even at high concentrations. The mono substituted derivatives of the C₂₁ dicarboxylic acid are prepared easily, and they provide unique properties for a variety of end uses. This paper illustrates the potential industrial applications for the dibasic acid and some of its derivatives in ink resins; adhesives; coatings; lubricants; plasticizers; corrosion inhibitors; synthetic coolants; emulsions; temporary coatings; floor polishes; and industrial, household, and institutional cleaners.     

Redesign of the substrate specificity of human cathepsin D: the dominant role of position 287 in the S2 subsite

Interest in the active site specificity of human cathepsin Dstems from the search for specific therapeutic agents againstmany of the sequentially and structurally homologous membersofthe aspartic proteinase family. The work presented here examinedone amino acid in the cathepsin D sequence, located in the S₂subsite, which contributes substantially to the specificityof enzyme-Ugand interactions at the enzyme active site. Previousstudies reported on the specificity of binding and catalysisby native and recombinant human cathepsin D explored throughkinetic studies using a systematic series of synthetic substrates.Utilizing a rulebased molecular model of human cathepsin D,Met287 was suggested as a candidate for mutagenesis to furtherexplore selectivity within the S₂ subsite of the cathepsin Dactive site. Met287 mutant derivatives of human cathepsin Dwere designed, expressed and characterized in kineticstudies.Native cathepsin D accommodates large hydrophobic residues inthe P₂ position of a substrate; positively charged residuesin P₂ are not favorable for catalysis.It was demonstrated thataltering Met287 of human cathepsin D to more polar amino acidsproduced active mutant enzymes with significantly altered substratespecificity.     

Biotransformation of saturated monohydroxyl fatty acids to 2-tetrahydrofuranyl acetic acid derivatives: Mechanism of formations and the biological activity of 5-n-hexyl-tetrahydrofuran-2-acetic acid

Transformation of 12-hydroxyoctadecanoic acid (12-HOA) to 5-n-hexyl-tetrahydrofuran-2-acetic acid (5-HTFA) byBacillus lentus NRRL B-14864 (B-14864) was carried out in the presence or absence of oligomycin, 2-bromooctanoic acid (2-BA), or sodium azide. In addition, several saturated and monounsaturated monohydroxyfatty acids, saturated monooxofatty acids, and monounsaturated fatty acid were used as substrates for transformation reactions by B-14864 or corynebacterium FUI-2. Methyl esters of the transformation products were analyzed by gas chromatography and gas chromatography/mass spectroscopy. Various γ-lactones and tetrahydrofuran fatty acid derivatives were conversion products when saturated monohydroxyfatty acids were used as substrates; the production of 5-HTFA from 12-HOA by B-14864 cells was completely inhibited in the presence of high concentration of oligomycin, 2-BA, or sodium azide; and fatty acid β-oxidation metabolic intermediates, 6-hydroxydodecanoic, 4-oxododecanoic, and 4-oxodecanoic acids were products when 12-HOA, 10-oxo-, and 12-oxooctadecanoic acids were used as substrates. Our results suggest that the production of 5-HTFA from 12-HOA by B-14864 was through the fatty acid β-oxidation pathway. Three-day-old driedfruit beetle pupae were topically treated with 5-HTFA to test for juvenile hormone activity, and 5-HTFA was found to possess juvenile hormone-like activity in pure form but not when it was diluted to 10%. Presented in part at the 37th West Central States Biochemistry Conference Annual Meeting, Columbia, Missouri, Oct. 1994.     

Review Oligosaccharide Synthesis Using Glycosidases*

A wide range of strategies may be considered for the synthesis of oligosaccharides in vitro using enzymes, all of which present significant challenges to the enzyme technologist. Many simple oligosaccharides may be produced by the hydrolysis of readily-available polysaccharides using specific enzymes. However, to produce the complex branched hetero-oligosaccharides of the types which occur N-linked to glycoproteins is more taxing. Materials of this type may be synthesised using the natural synthetic enzymes which employ sugar nucleotides as substrates. These enzymes are highly specific but they are costly to use due to their instability and to the cost of their substrates. It has been demonstrated that glycosidases are capable of synthesising hetero-oligosaccharides when provided with underivatised sugars in conditions of low water activity but that the specificity of synthetic reactions is apparently not high and that yields of material are low. Approaches to these problems are discussed, including the use of immobilised enzymes in packed-bed reactors to allow the ‘ping’ stage of the synthetic reaction to be separated in time from the ‘pong’ stage, and the application of aqueous two-phase systems which may be ‘tailored’ to separate the enzyme and the substrates from the final product. The ability to synthesise a range of oligosaccharides is dependent on the availability of appropriate glycosidases with differing specificities. There is a clear importance of ‘biodiversity’ in providing knowledge of sources of these.     

Using controlled radical polymerisation techniques for the synthesis of functional polymers containing amino acid moieties

There is great current interest in bridging the gap between robust synthetic polymers and complex biological polymers to allow for the preparation of novel functional, well‐defined, biocompatible and tailorable materials. In this mini‐review recent reports on the preparation of functional amino acid polymers using controlled radical polymerisation techniques are discussed. The future potential applications of these materials as well as the proposed further directions in the field are also highlighted. Copyright © 2010 Society of Chemical Industry