Addition of amines and carbon nucleophiles to vinyl sulfone-modified 6-deoxy-hex-3-enopyranoside: a case of nucleophile dependent diastereoselectivity

Reactions of amines and carbon nucleophiles with 4-sulfonyl-hex-3-enopyranoside generate a range of C-3 amino- and C-3 branched-chain sugars, which are analogues of 3-amino-3,6-dideoxy sugars and 3-C-branched-chain-3,6-dideoxy sugars. The diastereoselectivity of addition reaction is nucleophile dependent; while both nitrogen and carbon nucleophiles added in cis-fashion, amines generated C3-C4 trans-diaxial products (gulo-derivatives), and carbon nucleophiles afforded C3-C4 trans-diequatorial products (gluco-analogues).     

Methods of nitric oxide detection in plants: A commentary

Over the last decade nitric oxide (NO) has been shown to influence a range of processes in plants. However, when, where and even if NO production occurs is controversial in several physiological scenarios in plants. This arises from a series of causes: (a) doubts have arisen over the specificity of widely used 4,5-diaminofluorescein diacetate (DAF-2DA)/4-amino-5-methylamino-2,7-difluorofluorescein (DAF-FM) dyes for NO, (b) no plant nitric oxide synthase (NOS) has been cloned, so that the validity of using mammalian NOS inhibitors to demonstrate that NO is being measured is debatable, (c) the NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-l-oxyl-3-oxide (cPTIO) needs to be used with caution, and (d) some discrepancies between assays for in planta measurements and another based on sampling NO from the gas phase have been reported. This review will outline some commonly used methods to determine NO, attempt to reconcile differing results obtained by different laboratories and suggest appropriate approaches to unequivocally demonstrate the production of NO.     

Synthesis of New Benzimidazole‐1,2,3‐triazole Hybrids as Tyrosinase Inhibitors

A novel series of benzimidazole‐1,2,3‐triazole hybrids containing substituted benzyl moieties were designed, synthesized and evaluated for their inhibitory activity against mushroom tyrosinase. The results indicated that 2‐(4‐{[1‐(3,4‐dichlorobenzyl)‐1H‐1,2,3‐triazol‐4‐yl]methoxy}phenyl)‐1H‐benzimidazole ( 6g ) and 2‐(4‐{[1‐(4‐bromobenzyl)‐1H‐1,2,3‐triazol‐4‐yl]methoxy}phenyl)‐1H‐benzimidazole ( 6h ) exhibited effective inhibitory activity with IC₅₀ values of 9.42 and 10.34 μm , respectively, comparable to that of kojic acid as the reference drug (IC₅₀ = 9.28 μm ). Kinetic study of compound 6g confirmed mixed‐type inhibitory activity towards tyrosinase indicating that it can bind to free enzyme as well as enzyme‐substrate complex. Also, molecular docking analysis was performed to determine the binding mode of the most potent compounds ( 6g and 6h ) in the active site of tyrosinase. Consequently, 6g and 6h derivatives might serve as promising candidates in cosmetics, medicine or food industry, and development of such compounds may be of an interest.     

Highly selective and sensitive coumarin–triazole‐based fluorometric ‘turn‐off’ sensor for detection of Pb2+ ions

Exposure to even very low concentrations of Pb²⁺ is known to cause cardiovascular, neurological, developmental, and reproductive disorders, and affects children in particular more severely. Consequently, much effort has been dedicated to the development of colorimetric and fluorescent sensors that can selectively detect Pb²⁺ ions. Here, we describe the development of a triazole‐based fluorescent sensor L5 for Pb²⁺ ion detection. The fluorescence intensity of chemosensor L5 was selectively quenched by Pb²⁺ ions and a clear color change from colorless to yellow could be observed by the naked eye. Chemosensor L5 exhibited high sensitivity and selectivity towards Pb²⁺ ions in phosphate‐buffered solution [20 mM, 1:9 DMSO/H₂O (v/v), pH 8.0] with a 1:1 binding stoichiometry, a detection limit of 1.9 nM and a 6.76 × 10⁶ M^?1 binding constant. Additionally, low‐cost and easy‐to‐prepare test strips impregnated with chemosensor L5 were also produced for efficient of Pb²⁺ detection and proved the practical use of this test.     

Symmetric molecules with 1,4-triazole moieties as potent inhibitors of tumour-associated lactate dehydrogenase-A

A series of symmetric molecules incorporating aryl or pyridyl moieties as central core and 1,4-substituted triazoles as a side bridge was synthesised. The new compounds were investigated as lactate dehydro-genase (LDH, EC 1.1.1.27) inhibitors. The cancer associated LDHA isoform was inhibited with IC₅₀?=?117–174 µM. Seven compounds exhibited better LDHA inhibition (IC₅₀ 117–136 µM) compared to known LDH inhibitor – galloflavin (IC₅₀ 157 µM).     

In vitro cytotoxic and in vivo antitumoral activities of some aminomethyl derivatives of 2,4‐dihydro‐3H‐1,2,4‐triazole‐3‐thiones—Evaluation of their acetylcholinesterase and carbonic anhydrase enzymes inhibition profiles

The 1,2,4‐triazole and its derivatives were reported to exhibit various pharmacological activities such as antimicrobial, analgesic, anti‐inflammatory, antitumoural, cytotoxic, and antioxidant properties. In this study, a series of triazole compounds (M1‐M10) were evaluated for some biological activities. In vitro qualifications of these compounds on acetylcholinesterase (AChE) and human carbonic anhydrase enzyme activities were performed. Also, their antitumoral activities in human colon cancer (HT29) cell line cultures were examined. In addition, colon cancer experimentation was induced in rats by an in vivo method, and the in vivo anticancer effects of triazole derivatives were investigated. Also, the effects of these derivatives in levels of antioxidant vitamin A, vitamin E, and MDA were studied in rat liver and blood samples. Most of the compounds were found to exhibit significant antioxidant and antitumoral activities. All the compounds had cytotoxic activities on HT29 cell lines with their IC₅₀ values lower than 10 µM concentrations. The low IC ₅₀ values of the compounds are M1 (3.88 µM), M2 (2.18 µM), M3 (4.2 µM), M4 (2.58 µM), M5 (2.88 µM), M6 (2.37 µM), M7 (3.49 µM), M8 (4.01 µM), M9 (8.90 µM), and M10 (3.12 µM).     

Enantiomer separation of triazole fungicides by high-performance liquid chromatography

Enantiomer separation is one of the most important prerequisites for the investigation of environmental enantioselective behaviors for chiral pesticides. In the present study, the enantiomer separation of 7 triazole fungicides, i.e., hexaconazole (1), triadimefon (2), tebuconazole (3), diniconazole (4), flutriafol (5), propiconazole (6), and difenoconazole (7), were evaluated using normal phase high-performance liquid chromatography. Chrialcel OD column and Chrialcel OJ column were used. The influence of column temperature was studied for the optimization of the resolution as well as the type and percentage of organic modifier in the mobile phase. The retention factors for the enantiomers of all investigated compounds decreased as the temperature increased. The natural logarithms of the selectivity factors (lnalpha) of hexaconazole (1), tebuconazole (3), flutriafol (5), propiconazole (6) and difenoconazole (7) depended linearly on the inverse of temperature (1/T) while the corresponding values for triadimefon (2) and diniconazole (4) kept unchanged in the studied temperature range 10-35 degrees C. Van't Hoff plots afforded thermodynamic parameters, such as the apparent change in enthalpy DeltaH degrees , the apparent change in entropy DeltaS degrees and the apparent change in DeltaDeltaH degrees and DeltaDeltaS degrees . The thermodynamic parameters (DeltaH degrees , DeltaS degrees , DeltaDeltaH degrees and DeltaDeltaS degrees ) were calculated in order to provide an understanding of the thermosynamic driving forces for enantioseparation. The established method shows perspective to be used for preparing micro-scale amount of pure enantiomers of the chiral triazoles studied.     

Synthesis of 1-C-(tetra-O-acetyl-β-d-galactopyranosyl)-2,3-diiodo-1-propene and its reaction with primary amines

Iodination of 1-C-(tetra-O-acetyl-β-d-galactopyranosyl)allene affords an E/Z-mixture of 1-C-(tetra-O-acetyl-β-d-galactopyranosyl)-2,3-diiodo-1-propene. S_N2 displacement of the allylic iodide with primary amines affords an E/Z-mixture of allylic amines under a variety of conditions. Due to its experimental simplicity and low cost of reagents, this procedure may find wide use in the laboratory for functionalization of sugar allenes.     

Syntheses and structures of vinyl and aryl derivatives of carbonyl halide iron complexes

cis,trans-Fe(CO)₂(PMe₃)₂(p-Y-C₆H₄)X [X=Br, Y=H (4a), MeO (4b), Cl (4c), F (4d), Me (4e); X=I, Y=H (5); X=Cl, Y=H (6)] and cis,trans-Fe(CO)₂(PMe₃)₂(σ-CHCH₂)X [X=Br (7); X=I (8); X=Cl (9)] are prepared by reacting dihalide complexes cis,trans,cis- Fe(CO)₂(PMe₃)₂X₂ [X=Br (1), X=I (2), X=Cl (3)] with Grignard reagents p-Y-C₆H₄-MgBr (Y=H, OMe, Cl, F, Me) or CH₂CH-MgBr and with lithium reagents PhLi, CH₂CH-Li. With both reagents, the reaction proceeds following two parallel pathways: one is the metallation reaction which yields alkyl derivatives, the other affords 17 electron complexes [Fe(CO)₂(PMe₃)₂X] via monoelectron reductive elimination. The influence of the halides and organometallic reagents on the yield of the metallation reaction is discussed. The solution structure of the complexes is assigned on the basis of IR and ¹H, ¹³C, ¹⁹F, ³¹P NMR spectra. The solid state structure of complexes 4a, 5 and 6 is determined by single crystal X-ray diffractometric methods.     

Regiospecific alkaline protease-catalyzed divinyl acyl transesterifications of primary hydroxyl groups of mono- and di-saccharides in pyridine

This paper describes highly selective transesterification reactions, catalyzed by an alkaline protease from Bacillus subtilis in pyridine, of several mono- and di-saccharides with divinyl dicarboxylates ranging from 4 to 10 carbon atoms. A series of polymerizable vinyl fatty acid sugar esters were obtained with good selectivity and high yields. Most products had high proportions of the alpha anomer. The influences of the enzymes, solvents, temperature, and acyl donor chain length on the reaction were studied. Vinyl sugar esters offer a new family of functional water-soluble monomers for preparation of sugar-containing polymers.