A novel multicomponent reaction: easy access to ferrocenyl (alkylimino)-1,4-dihydroquinolines

A facile and rapid synthetic approach of ferrocenyl (alkylimino)-1,4-dihydroquinolines through a novel multicomponent reaction is described. This strategy is high yielding (60-90%). The easy removal of the ferrocenyl entity led to formation of substituted quinolines by microwave method.     

A Practical and Inexpensive One‐Pot Synthesis of Bis(indenyl)­dimethyltitanium with Aqueous Workup Procedure

A simple, reliable, and reproducible procedure for the multi‐gram synthesis of highly pure bis(indenyl)dimethyltitanium is presented. The procedure relies on a one‐pot conversion of inexpensive indene, methyllithium, and titanium tetrachloride to [Ind₂TiMe₂] and a convenient and quick aqueous workup protocol. Overall, quantities of several grams of [Ind₂TiMe₂] can be synthesized within a few hours. The procedure can also be used for the synthesis of [Cp₂TiMe₂] from cyclopentadiene, methyllithium, and titanium tetrachloride.     

Synthetic Biology Enables Programmable Cell-Based Biosensors

Cell-based biosensors offer cheap, portable and simple methods of detecting molecules of interest but have yet to be truly adopted commercially. Issues with their performance and specificity initially slowed the development of cell-based biosensors. With the development of rational approaches to tune response curves, the performance of biosensors has rapidly improved and there are now many biosensors capable of sensing with the required performance. This has stimulated an increased interest in biosensors and their commercial potential. However the reliability, long term stability and biosecurity of these sensors are still barriers to commercial application and public acceptance. Research into overcoming these issues remains active. Here we present the state-of-the-art tools offered by synthetic biology to allow construction of cell-based biosensors with customisable performance to meet the real world requirements in terms of sensitivity and dynamic range and discuss the research progress to overcome the challenges in terms of the sensor stability and biosecurity fears.     

A new resampling method for sampling designs without replacement: the doubled half bootstrap

A new and very fast method of bootstrap for sampling without replacement from a finite population is proposed. This method can be used to estimate the variance in sampling with unequal inclusion probabilities and does not require artificial populations or utilization of bootstrap weights. The bootstrap samples are directly selected from the original sample. The bootstrap procedure contains two steps: in the first step, units are selected once with Poisson sampling using the same inclusion probabilities as the original design. In the second step, amongst the non-selected units, half of the units are randomly selected twice. This procedure enables us to efficiently estimate the variance. A set of simulations show the advantages of this new resampling method.     

Synthesis of a 4-Deoxy-4-C-Methylene Analog of Glucosylceramide

Abstract

D-Glucose was transformed into 2,3:5,6-di-O-isopropylidene dithioacetal 1; its oxidation to ketone 2 and subsequent Wittig reaction afforded 4-deoxy-4-C-methylene derivative 3. Hydrolytic removal of the protective groups, then O-acetylation, selective anomeric O-deacetylation, and base catalyzed trichloroacetonitrile addition furnished 4-deoxy-4-C-methylene substituted glycopyranosyl donor 7 as an anomeric mixture. Reaction of 7 with azidosphingosine derivative 8 under BF₃-OEt₂ catalysis gave β-glycopy-ranoside 9. Azido group reduction with triphenylphospnine in the presence of palmitic anhydride and water afforded directly O-acyl protected glycosphingolipid derivative 10 which yielded after Zemplen O-deacylation target molecule 11     

Alkaline phosphatase enzymatic signal amplification for fast, sensitive impedimetric DNA detection

Enzymatic signal amplification by the deposition of insoluble product on the electrode surface enhances impedimetric DNA detection sensitivity. This work demonstrates a method which gives the required detection sensitivity at significantly reduced enzyme reaction times, and demonstrates the capability for DNA SNP discrimination of biologically relevant sequences. This opens up the prospect of more rapid and relevant multiparameter impedimetric bioassays.     

A Five-Step Synthesis of (±)-Tylophorine via a Nitrile-Stabilized Ammonium Ylide

The Stevens rearrangement of a nitrile-stabilized ammonium ylide is the key step of a very short and practical synthesis of the phenanthroindolizine alkaloid (±)-tylophorine. The method requires only five linear steps and is devoid of any protecting group manipulations.     

Donellanic acids A–C: new cyclopropanic oleanane derivatives from Donella ubanguiensis (Sapotaceae)

Three new cyclopropanic oleanane triterpenoids and ten known compounds were obtained from Donella ubanguiensis using chromatographic methods. The structures were established on the basis of mass spectrometric and NMR data and by comparison with values reported in the literature. The structures of the new compounds were confirmed by X-ray crystallography. A part of the isolated compounds was evaluated for cytotoxic and antimicrobial activities.     

Simulation of Student–Lévy processes using series representations

Lévy processes have become very popular in many applications in finance, physics and beyond. The Student–Lévy process is one interesting special case where increments are heavy-tailed and, for 1-increments, Student t distributed. Although theoretically available, there is a lack of path simulation techniques in the literature due to its complicated form. In this paper we address this issue using series representations with the inverse Lévy measure method and the rejection method and prove upper bounds for the mean squared approximation error. In the numerical section we discuss a numerical inversion scheme to find the inverse Lévy measure efficiently. We extend the existing numerical inverse Lévy measure method to incorporate explosive Lévy tail measures. Monte Carlo studies verify the error bounds and the effectiveness of the simulation routine. As a side result we obtain series representations of the so called inverse gamma subordinator which are used to generate paths in this model.