Voltammetric Assay of Naproxen in Pharmaceutical Formulations Using Boron‐Doped Diamond Electrode

The electrooxidation of naproxen was studied, for the first time, using boron‐doped diamond (BDD) electrode by cyclic and differential pulse voltammetry (CV and DPV) in nonaqueous solvent supporting electrolyte system. The results were also compared with glassy carbon electrode (GC) under the same conditions. Naproxen undergoes one electron transfer resulting in the formation of cation radical for the first electrooxidation step, which follows other chemical and electrochemical steps such as deprotonation, removal of another electron and the attack of nucleophile (ECEC mechanism). BDD electrode provided higher signal to background ratio, well resolved and highly reproducible cyclic voltammograms than the GC electrode. With a scan rate of 50 mV s^?1 and pulse height of 50 ms, respectively, the DPV technique was able to determine the naproxen concentrations in the range of 0.5 to 50 μM with a detection limit of 30 nM. The influence of interference compounds namely 2‐acetyl‐6‐methoxy naphthalene (AMN) on naproxen oxidation can also be followed successfully. Moreover, the percentage of AMN present in the standard chemical form of a mixture containing naproxen can be found accurately. Rapidity, precise and good selectivity were also found for the determination of naproxen in pharmaceutical formulations.     

苯甲醚在复合催化剂上的催化酰化

复合催化剂首次用于催化苯甲醚与酰化剂乙酰氯的酰化反应.发现不同沸石的单独使用仅给出很低产率的对-甲氧基苯乙酮.但是由HY沸石(硅铝比=40)或USY(超稳Y沸石)和SnO组成的复合催化剂的催化活性比单独使用沸石时高得多.增加由USY沸石和不同量的SnO组成的复合催化剂中的SnO的量,导致对-甲氧基苯乙酮产率的提高.由H型沸石(HY和H-ZSM-5沸石)和SnO组成的复合催化剂在苯甲醚与乙酰氯的酰化反应中的催化活性主要取决于所用沸石的硅铝比.     

Retention characteristics of aliphatic compounds on cellulose acetates as a stationary phase with an aqueous mobile phase

Summary Cellulose and cellulose mono-, di-, and triacetate were used as stationary phases for liquid chromatography with water as a mobile phase, and the retention behavior of alcohols, ethers, ketones, and chlorides was examined. For cellulose acetate columns, the logarithm of the specific retention volume, (logV _g ^* ), correlated linearly with the logarithm of partition coefficient between 1-octanol and water (log K_o/w), for each homologous group, but all solutes were unretained on cellulose columns. With the exception of chlorides, the intercept values of the log V _g ^* –log K_o/w regression lines increased significantly with increase of acetyl content of cellulose acetates, but the slopes of the regression lines changed little. This suggests that hydrophobic interaction between the acetyl groups of cellulose acetates and the alkyl chains of the solutes is the dominant factor in the retention.The capacity factors for 1-alcohols with cellulos diacetate column indicated a maximum at a column temperature of about 40°C. This unique retention behavior was assumed to be caused by small structural change of the cellulose acetate polymer, because this temperature effect on the retention corresponded with effects observed by differential scanning calorimetry (DSC).     

Analysis of the potato glycoalkaloids by using of enzyme biosensor based on pH-ISFETs

The applicability of an enzyme biosensor based on pH-ISFETs for direct determination of total glycoalkaloids content in real potato samples, without any pre-treatment, is shown. The results of determination of the total glycoalkaloids concentrations in potato samples from different experimental varieties obtained by the biosensor are well correlated with the analogous data obtained by the HPLC method with standard complex sample pre-treatment procedure. The detection of total glycoalkaloids content by biosensors is reproducible, the relative standard deviation was around 3%. The dependence of total glycoalkaloids content on various parts of the potato tuber and their size, different growing area has been shown using the biosensor developed.The method based on biosensors is cheap, easy to operate and requires a shorter analysis time than the one needed using traditional methods for glycoalkaloids determination. The biosensor can operate directly on potato juice, or even directly on a suspension of potato or plant material. It can provide a way to save time and costs, with a possibility of taking rapid assessment of total glycoalkaloids content in a wide variety of potato cultivars. Furthermore the operational and storage stability of this biosensor are quite good with a drift lower than 1% per day and response being stable for more than 3 months.     

α-硝基二硫缩烯酮的制备

近年来，结合烷硫基对α-羰基二硫缩烯酮反应的调控作用，我们开展了α-羰基二硫缩烯酮／二硫缩烯酮α-官能化(或α-位修饰)的研究，以期扩展二硫缩烯酮在合成中的应用。在用α-碘代脱羧和α-溴代脱乙酰基反应分别成功地制备了α-碘代-α’-肉桂酰基二硫缩烯酮Ⅲ和α-溴代二硫缩烯酮嘲的基础     

Reaktionsverhalten von β-Oxo-carbonsäurederivaten der Anthracenreihe bei der Synthese von Thiophenen

Summary -Oxo-1-anthracenepropionate (3) reacts step by step with phenylisothiocyanate and -CH-acidic halo compounds to keten-S,N-acetals4, followed by cyclocondensation to give the 4-(1-anthracenyl)-thiophene-3-carboxylates5. In contrast, the reaction of -oxo-9-anthracenepropionate (6) with isothiocyanates and -CH-acidic halo compounds yields 5-acyl-2-amino-3-(9-anthracenoyl)-4-hydroxy-thiophenes8. This is caused by the sterical hindrance of the keto group of the anthracene in position 9; thus, the cyclocondensation proceedsvia reaction of the ester group of the -oxo-propionate. In the same way, 9-acetylanthracene reacts with phenylisothiocyanate and -CH-acidic compounds to keten-S,N-acetals10 and, in an additional step, to 2-anilino-3-(9-anthracenoyl)-thiophenes11 and 2-(9-anthracenoyl)-methylene-3,4-diphenyl-2,3-dihydro-(1,3)-thiazole12, respectively. The structure of all new compounds was determinated by 2D NOESY NMR spectroscopy.

Herrn Prof. Dr. habil.G. Großmann zum 65. Geburtstag gewidmet     

Dithiirane or thiosulfine intermediates in the reaction of acetyl diaroylchloromethyl disulfides with secondary amines?

Summary Since 1979,Senning's acetyl dibenzoylchloromethyl disulfide has been known as one of the first thiosulfine/dithiirane precursors. Its reactions with an excess of morpholine fulfill three advantageous conditions at once: thiosulfine or dithiirane species are intercepted by intermolecular additions, without heating, and without rearrangements. In the present work, reactions between a series of new acetyl diaroylchloromethyl disulfides ((4-X-C₆H₄-CO)₂-CCl-SSCOCH₃;X=F, Cl, Br, CH₃, and CH₃O) and an excess of morpholine are studied. As dominating products, 2-(4-morpholinyldithio)-1,3-diaryl-1,3-propanediones are obtained. The reactions are complete within several seconds. In order to obtain high yields of interception products, the mixtures have to be worked up within a few minutes. From the observation of high reaction rates at room temperature, a new reaction mechanism is deduced that involves the initial formation of dithiirane species (alone or before thiosulfine species).Dedicated to Prof.Peter K. Claus on the occasion of his 60th birthday     

The reaction of Ru3(CO)12 with 1,4-dichloro-but-2-yne in basic methanolic solution. Synthesis and crystal structure of (μ-H)2Ru3(CO)9{μ3-η-[H2CC(H)CCC(O)OCH3]}

The title complex is obtained by reacting Ru₃(CO)₁₂ with 1,4-dichloro-but-2-yne (ClCH₂CCCH₂Cl, DCB) in CH₃OH/KOH solution (followed by acidification with HCl). The X-ray structure analysis shows that (μ-H)₂Ru₃(CO)₉{μ₃-η²-[H₂CC(H)CCC(O)OCH₃]} complex contains a “parallel” ene-yne acetyl substituent, H₂CC(H)CCC(O)OCH₃; the formation of such a ligand starting from DCB is - to our knowledge - unprecedented. The synthesis of complex (μ-H)₂Ru₃(CO)₉{μ₃-η²-[H₂CC(H)CCC(O)OCH₃]} occurs through the activation of CO and methanol. This process has been found for other reactions of functionalized alkynes with M₃(CO)₁₂ carbonyls (M = Fe, Ru) under basic methanolic conditions.The known hydridic cluster, (μ-H)Ru₃(CO)₉[μ₃-η³-(MeCCHCH)] has been identified as the minor reaction product.     

Stereoselective ring-opening reactions with AcBr and AcCl. A new method for preparation of some haloconduritols

The actions of AcX (X=Br, Cl) on 7-oxa-bicyclo[2.2.1]hept-5-ene-2,3-diol diacetates and a transoid-epoxide prepared from the acetonide of cyclohexa-3,5-diene-cis-1,2-diol were studied. H₂SO₄-catalyzed cleavage of exo-cis-7-oxa-bicyclo[2.2.1]hept-5-ene-2,3-diol diacetate with AcCl gave (1α,2α,3α,6β)-6-chloro-4-cyclohexene-1,2,3-triol triacetate, from which the corresponding chloroconduritol was obtained by trans-esterification (MeOH/HCl). A similar reaction of the exo-diacetate with AcBr in the presence of H₂SO₄ resulted in bromine addition. The formation of bromine from the reaction of AcBr and H₂SO₄ was observed by independent experiments. H₂SO₄-catalyzed reaction of endo-cis-7-oxa-bicyclo[2.2.1]hept-5-ene-2,3-diol diacetate with AcX (X=Br, Cl) gave (1α,2α,3β,6β)-6-halo-4-cyclohexene-1,2,3-triol triacetates. The reaction of the transoid-epoxide with AcX (X=Br, Cl) with no catalyst gave also (1α,2α,3β,6β)-6-halo-4-cyclohexene-1,2,3-triol triacetates.     

Non-Alkaloid Cholinesterase Inhibitory Compounds from Natural Sources

Alzheimer’s disease (AD) is a severe neurodegenerative disorder of different brain regions accompanied by distresses and affecting more than 25 million people in the world. This progressive brain deterioration affects the central nervous system and has negative impacts on a patient’s daily activities such as memory impairment. The most important challenge concerning AD is the development of new drugs for long-term treatment or prevention, with lesser side effects and greater efficiency as cholinesterases inhibitors and the ability to remove amyloid-beta(Aβ) deposits and other related AD neuropathologies. Natural sources provide promising alternatives to synthetic cholinesterase inhibitors and many have been reported for alkaloids while neglecting other classes with potential cholinesterase inhibition. This review summarizes information about the therapeutic potential of small natural molecules from medicinal herbs, belonging to terpenoids, coumarins, and phenolic compounds, and others, which have gained special attention due to their specific modes of action and their advantages of low toxicity and high efficiency in the treatment of AD. Some show superior drug-like features in comparison to synthetic cholinesterase inhibitors. We expect that the listed phytoconstituents in this review will serve as promising tools and chemical scaffolds for the discovery of new potent therapeutic leads for the amelioration and treatment of Alzheimer’s disease.