Search

Carbon emissions from industrial sources are of major global concern, especially contributions from the steel manufacturing process which accounts for the majority of emissions. Typical blast furnace gases consist of CO2 (20-25%), CO (20-25%), H2 (3-5%) and N2 (40-50%) and trace amounts of other gases. It is demonstrated that gas mixtures with these compositions can be used at atmospheric pressure to grow carbon nanotubes (CNTs) by chemical vapor deposition (CVD) on to steel substrates, which act as catalysts for CNT growth. Computational modelling was used to investigate the CNT growth conditions inside the CVD chamber. The results show that industrial waste pollutant gases can be used to manufacture materials with significant commercial value, in this case CNTs.

In metabolic glycoengineering (MGE), cells or animals are treated with unnatural derivatives of monosaccharides. After entering the cytosol, these sugar analogues are metabolized and subsequently expressed on newly synthesized glycoconjugates. The feasibility of MGE was first discovered for sialylated glycans, by using N-acyl-modified mannosamines as precursor molecules for unnatural sialic acids. Prerequisite is the promiscuity of the enzymes of the Roseman–Warren biosynthetic pathway. These enzymes were shown to tolerate specific modifications of the N-acyl side chain of mannosamine analogues, for example, elongation by one or more methylene groups (aliphatic modifications) or by insertion of reactive groups (bioorthogonal modifications). Unnatural sialic acids are incorporated into glycoconjugates of cells and organs. MGE has intriguing biological consequences for treated cells (aliphatic MGE) and offers the opportunity to visualize the topography and dynamics of sialylated glycans in vitro, ex vivo, and in vivo (bioorthogonal MGE).

Triene (III) prepared by coupling of the (S)-alcohol (I) with phosphate (II) undergoes ring-closing metathesis to produce the bicyclic phosphate (IV) having a conformationally fixed P-stereogenic center.

Chemical investigation of a marine actinomycete within the family Streptomycetaceae (our strain CNQ-149) has led to the isolation of the unprecedented alkaloids, actinobenzoquinoline (1) and actinophenanthrolines A-C (2-4). The chemical structures of 1-4 were assigned by interpretation of NMR spectroscopic data, and their absolute configurations were assigned by X-ray analysis. Actinobenzoquinoline possesses a 5-methyloxazolidin-4-one moiety and a dihydrobenzo[h]quinoline core structure, while actinophenanthrolines A-C are composed of hydroxypropanamide-substituted 1,7-phenanthroline core skeletons.

The importance of C–H bond activation in a simple molecule to form a molecule with enhanced functionality can be easily understood from a study of biological processes at a molecular level where, for example, a specific enzyme selectively activates a chemically inert C–H bond and functionalizes it to a useful product. This strategy is now being used for large scale industrial processes and has both social and environmental benefits. C–H bond functionalization is also of major importance in catalysis because of the possibility of constructing complex structural motifs from relatively simple precursors. However, functionalization of a chemically inert C–H bond needs specific catalysts or reaction conditions that can selectively activate a particular C–H bond, leaving others intact. To achieve this target, various metal catalyzed or mediated reactions have been employed. Keeping the growing importance of this emerging field in mind, we now present recent advances in the field of C–H activation and functionalization using group 10 transition metal catalysts. Attempts have also been made to discuss the future of group 10 transition metals in catalysis.

A variety of aromatic and aliphatic aldehydes are difluoroallylated by the title difluoroalkene (I) leading to fluorinated methylenealkanols (III) in good to excellent yields.

The relative and absolute configurations of potent antifungal agents leupyrrin A1 (I) and B1 (II) are determined by a combination of high field NMR studies, molecular modeling, and chemical derivatization.

The synthesis of the tricyclus (VI), which is a useful precursor for the preparation of Lycopodium alkaloids involves a Diels—Alder cycloaddition and the cyclization of amine (V) as the key steps.

Chain extension of boronic esters by the action of configurationally labile racemic lithium carbenoids in the presence of scalemic bisoxazoline ligands was explored for the enantioselective synthesis of the two title product classes. Enantioenriched 2° carbinols generated by oxidative work-up (NaOOH) of initial α-phenylalkylboronate products were obtained in 35–83% yield and 70–96% ee by reaction of B-alkyl and B-aryl neopentyl glycol boronates with a combination of O-(α-lithiobenzyl)-N,N-diisopropylcarbamate and ligand 3,3-bis[(4S)-4,5-dihydro-4-isopropyloxazol-2-yl] pentane in toluene solvent (−78 °C to rt) with MgBr2·OEt2 additive. Enantioenriched α-(dimethylsilylphenylsilyl)alkylboronates were obtained in 35–69% yield and 9–57% ee by reaction of B-alkyl pinacol boronates with a combination of lithio(dimethylphenylsilyl)methyl 2,4,6-triisopropylbenzoate and ligand 2,2-bis[(4S)-4,5-dihydro-4-isopropyloxazol-2-yl]propane in cumene solvent (−45 °C to −95 °C to rt). The stereochemical outcome of the second type of reaction depended on the temperature history of the organolithium·ligand complex indicating that the stereoinduction mechanism in this case involves some aspect of dynamic thermodynamic resolution.

Peptoids (N-substituted glycines) are mimics of α-peptides in which the side chains are attached to the backbone N (α) -amide nitrogen instead of the C (α) -atom. Peptoids hold promise as therapeutics since they often retain the biological activity of the parent peptide and are stable to proteases. In recent years, peptoids have attracted attention as new potential antibiotics against multiresistant bacteria. Here we describe the submonomer solid-phase synthesis of an antimicrobial peptoid, H-Nmbn-Nlys-Nlys-Nnap-Nbut-Nmbn-Nlys-NH2.

Lithiation of stereodefined chloroalkyl sulfones (I) and (IX), treatment with carbonyl compounds, and subsequent base promoted ring closure gives cis/trans-mixtures of epoxides.

Upon deprotonation, title compounds (I) undergo ring contraction to the corresponding quinolone-2,4-diones (II) with high enantioselectivity.

N-Methylimidazole is an efficient additive in the formal cycloaddition of aldimines with homophthalic anhydride to improve yields as well as the regioselectivity with regard to cyclization over elimination.

The fate of the aryl gold(I) carbenes generated by retro-Buchner reaction of ortho-substituted 7-aryl-1,3,5-cycloheptatrienes is dependent on the constitution of the ortho substituent. Indenes and fluorenes are obtained by intramolecular reaction of highly electrophilic gold(I) carbenes with alkenes and arenes. According to density functional theory calculations, the gold-catalyzed retro-Buchner process occurs stepwise, although the two carbon–carbon cleavages occur on a rather flat potential energy surface.

A one-pot, sequential protocol is reported that involves complementary ambiphile pairing (CAP) of a vinyl sulfonamide with a variety of unprotected amino acids via aza-Michael addition and subsequent intramolecular amidation. The method generates diverse, sp3-rich mono- and bicyclic acyl sultams in a highly scalable manner. Modular pairing of stereochemically rich building blocks allows quick access to all possible isomers. Extension to include one-pot, sequential 3-, 4-, and 5-multicomponent protocols is also discussed.

Four putative functionalized α-chloroakyllithiums RCH2CHLiCl, where R=CHCH2 (18 a), CCH (18 b), CH2OBn (18 c), and CH[O(CH2)2O] (18 d), were generated in situ by sulfoxide–lithium exchange from α-chlorosulfoxides, and investigated for the stereospecific reagent-controlled homologation (StReCH) of phenethyl and 2-chloropyrid-5-yl (17) pinacol boronic esters. Deuterium labeling experiments revealed that α-chloroalkyllithiums are quenched by proton transfer from their α-chlorosulfoxide precursors and it was established that this effect compromises the yield of StReCH reactions. Use of α-deuterated α-chlorosulfoxides was discovered to ameliorate the problem by retarding the rate of acid-base chemistry between the carbenoid and its precursor. Carbenoids 18 a and 18 b showed poor StReCH efficacy, particularly the propargyl group bearing carbenoid 18 b, the instability of which was attributed to a facile 1,2-hydride shift. By contrast, 18 d, a carbenoid that benefits from a stabilizing interaction between O and Li atoms gave good StReCH yields. Boronate 17 was chain extended by carbenoids 18 a, 18 b, and 18 d in 16, 0, and 68 % yield, respectively; α-deuterated isotopomers D-18 a and D-18 d gave yields of 33 and 79 % for the same reaction. Double StReCH of 17 was pursued to target contiguous stereodiads appropriate for the total synthesis of (−)-epibatidine (15). One-pot double StReCH of boronate 17 by two exposures to (S)-D-18 a (≤66 % ee), followed by work-up with KOOH, gave the expected stereodiad product in 16 % yield (d.r.∼67:33). The comparable reaction using two exposures to (S)-D-18 d (≤90 % ee) delivered the expected bisacetal containing stereodiad (R,R)-DD-48 in 40 % yield (≥98 % ee, d.r.=85:15). Double StReCH of 17 using (S)-D-18 d (≤90 % ee) followed by (R)-D-18 d (≤90 % ee) likewise gave (R,S)-DD-48 in 49 % yield (≥97 % ee, d.r.=79:21). (R,S)-DD-48 was converted to a dideuterated isotopomer of a synthetic intermediate in Corey’s synthesis of 15.

The isolation and structure elucidation of a new meroterpenoid, actinoranone (1), produced by a marine bacterium closely related to the genus Streptomyces is reported. Actinoranone is composed of an unprecedented dihydronaphthalenone polyketide linked to a bicyclic diterpenoid. The stereochemistry of 1 was defined by application of the advanced Mosher’s method and by interpretation of spectroscopic data. Actinoranone (1) is significantly cytotoxic to HCT-116 human colon cancer cells with an LD50 = 2.0 μg/mL.

All distinct diastereoisomers of a contiguous stereotriad motif were separately targeted by a triple chain extension of B-phenethyl boronic esters using four unique presentation sequences of enantiomorphs of 1-[2H]-1-chloro-2-(1,3-dioxolan-2-yl)ethyllithium. The (R)- or (S)-configured chloroalkyllithium reagents were generated by sulfoxide–lithium exchange from the appropriate scalemic p-tolyl chloroalkyl sulfoxides using phenyllithium (THF, −78 °C). Stereotriad synthesis was accomplished in a single reaction vessel [7–19% yield, typical dr ≥ 74 (target):26 (∑ all other isomers)] and implemented by a simple algorithm consisting of reagent charging and temperature cycling events.

Raman microscopy systems are becoming increasingly widespread and accessible for characterising chemical species. Microfluidic systems are also progressively finding their way into real world applications. Therefore, it is anticipated that the integration of Raman systems with microfluidics will become increasingly attractive and practical. This review aims to provide an overview of Raman microscopy-microfluidics integrated systems for researchers who are actively interested in utilising these tools. The fundamental principles and application strengths of Raman microscopy are discussed in the context of microfluidics. Various configurations of microfluidics that incorporate Raman microscopy methods are presented, with applications highlighted. Data analysis methods are discussed, with a focus on assisting the interpretation of Raman-microfluidics data from complex samples. Finally, possible future directions of Raman-microfluidic systems are presented.

Starting from (I) the synthesis of a variety of new bicyclic sultams of type (IV), (VI), (XII), (XIV), and (XVI) is described.

A novel one-pot sulfonylation/intramolecular thia-Michael protocol is reported for the synthesis of 1,5,2-dithiazepine 1,1-dioxides. Sulfonylation between cysteine ethyl ester/cysteamine and 2-chloroethanesulfonyl chloride, followed by in situ intramolecular thia-Michael addition, was achieved and afforded the titled 1,5,2-dithiazepine-1,1-dioxide scaffolds. Diversification was demonstrated for future library synthesis.

A novel protocol is developed to prepare 2H-1,2,3-triazoles, functionalized with a boronate moiety at C-4 such as the pharmaceutically important system (VI) and its Thp analogue (IX).

Title compounds can be synthesized by stepwise one-pot reaction of aryl carboxylic acids with hydrazines followed by ring closure in the presence of thioxoacetate (IV).

A reaction sequence involving three consecutive microwave-promoted continuous-flow reaction steps is presented to synthesize the title compounds (V) and (VII).

Biquinolyl BQU catalyzes the addition of trimethylsilyl cyanide to aldehydes, ketones, and N-benzylaldimines to give the expected cyanohydrin and Strecker adducts by subsequent desilylation.

Treatment of tertiary benzylic alcohols with SOCl2 or HCl followed by reaction with AlMe3 or AlEt3 allows access to various tert-alkyl benzenes.

Knoevenagel condensation between benzoylacetonitriles and aromatic aldehydes affords colored α-cyano chalcones.

After the synthesis of the compounds (II) and (IV) the used norbornenyl-tagged reagents can be reacted with the norbornene group in a ring-opening metathesis polymerization and easily separated by filtration.

Treatment of vinylsulfonamides (I) and (IV) with amines in the presence of DBU results in elimination of the Tbs-ether moiety and subequent double aza-Michael reaction to give thiadiazepane dioxides.

An atom-economical protocol for the synthesis and purification of the compounds (III) and (V) is presented.

Raman spectroscopyallows visualizationof 2D and3D chemical distributions at highspatial resolution in a wide range of samples. It is insensitive to water, which makes it particularly attractive for applications in the biological sciences. At the same time, technical advances have allowed the laser excitation power to be reduced on thermally sensitive samples, without sacrificing acquisition times. This review highlights the analytical and diagnostic potential of Raman imaging techniques by reference to recent studies of red blood cells. In the case of red blood cells infected with low-pigmented forms of the malaria parasite, molecular images reveal sub-micron-inclusions of haemozoin, which suggests that the technique has potential for early-stage diagnosis of the disease.

A mild and convenient approach to the synthesis of title compounds (III) and (IX) is based on Pd-catalyzed amination of heteroaryl chlorides with primary amines.

Six new anthraquinone-γ-pyrones, saliniquinones A-F (1-6), which are related to metabolites of the pluramycin/altromycin class, were isolated from a fermentation broth of the marine actinomycete Salinispora arenicola (strain CNS-325). Their structures were determined by analysis of one- and two-dimensional NMR spectroscopic and high-resolution mass spectrometric data. The relative and absolute configurations of compounds 1-6 were determined by analysis of NOESY NMR spectroscopic data and by comparison of circular dichroism and optical rotation data with model compounds found in the literature. Saliniquinone A (1) exhibited potent inhibition of the human colon adenocarcinoma cell line (HCT-116) with an IC50 of 9.9 × 10-9 M. In the context of the biosynthetic diversity of S. arenicola, compounds 1-6 represent secondary metabolites that appear to be strain specific and thus occur outside of the core group of compounds commonly observed from this species.

The stable benzyl azide (I) containing a boronate ester allows regioselective 1,3-dipolar cycloaddition with terminal olefins followed by a Cu-catalyzed Suzuki coupling of the resulting triazoles such as (IIIa).

The feature of the title method is the complementary pairing of the two ambiphilic synthons, o-fluorobenzenesulfonamide and ortho-quinone methide, in a formal one-pot [4 + 4] approach to afford the novel dibenzooxathiazocine-2,2-dioxide scaffold.