Oligoamide,a new lactam from the leaves of Angylocalyx oligophyllus

A new lactam, oligoamide (1), along with three known compounds (2–4), stigmasterol-3-O-β-D-glucopyranoside (2), formononetin (3) and (-)-pinitol (4) were isolated from the CH₂Cl₂/CH₃OH (1:1) extract of the leaves of Angylocalyx oligophyllus by chromatographic separation. Their structures were elucidated on the basis of spectroscopic analysis (UV, IR, MS, 1D, and 2D NMR). Compound 1 was found to have weak antioxidant and urease inhibitory potential.     

Multiple regioselective functionalizations of quinolines via magnesiations

A wide range of polyfunctionalized quinolines was prepared via chemo- and regioselective magnesiation reactions using appropriate Mg reagents, such as i-PrMgCl.LiCl, MesMgBr.LiCl, Mes2Mg.2LiBr, TMPMgCl.LiCl, and TMP2Mg.2LiCl. An application to the total synthesis of the biologically active compound talnetant was performed (six steps, 28%).     

Investigating comprehensive two-dimensional gas chromatography conditions to optimize the separation of oxygenated compounds in a direct coal liquefaction middle distillate

Considering the global energetic context, diversifying fuels is of growing importance and many new alternatives are promising. Coal liquefaction products definitely appear among the new generation substitutes. These product's characteristics are very far from fuel specifications as they are mainly composed of naphthenes, aromatics, polycondensed naphthenic and aromatic structures and heteroatomic compounds (nitrogen and oxygen), with a very low paraffin content. Identification and quantification of oxygen-containing species in coal-derived liquids are of considerable importance to understand their behaviors in further processing. However, these species have not been characterized as fully as the predominant hydrocarbon components. Literature shows that these compounds consist mainly in alkylated phenolic and furanic structures. Therefore, comprehensive two-dimensional gas chromatography has been investigated to provide enhanced molecular characterization of these complex samples. Several different configurations involving innovative column configurations were tested. Each of them was optimized by testing different column lengths, modulation periods, and oven conditions. A comparison of the contribution of each column configuration was carried out regarding four main criteria: individual separation of oxygenates, group type separation, resolution, and space occupation. One of them enabled an outstanding separation of paraffins, naphthenes, monoaromatics, diaromatics and targeted O-compounds in a direct coal liquefaction product. It was therefore subjected to further experimentations using a time-of-flight mass spectrometer to validate the identification and unravel more than fifty oxygenated molecular structures. A group-type quantification was also established for four column arrangements and gives the distribution of paraffins, naphthenes and aromatics. It can be concluded from this study that a non-orthogonal arrangement involving a highly polar column in the first dimension was the most adapted one.     

Using comprehensive two-dimensional gas chromatography for the analysis of oxygenates in middle distillates I. Determination of the nature of biodiesels blend in diesel fuel

In the current energetic context (increasing consumption of vehicle fuels, greenhouse gas emission etc.) government policies lead to mandatory introduction in fossil fuels of fuels resulting from renewable sources of energy such as biomass. Blending of fatty acid alkyl esters from vegetable oils (also known as biodiesel) with conventional diesel fuel is one of the solutions technologically available; B5 blends (up to 5%w/w esters in fossil fuel) are marketed over Europe. Therefore, for quality control as well as for forensic reasons, it is of major importance to monitor the biodiesel origin (i.e. the fatty acid ester distribution) and its content when it is blend with petroleum diesel. This paper reports a comprehensive two-dimensional gas chromatography (GC x GC) method that was developed for the individual quantitation of fatty acid esters in middle distillates matrices. Several first and the second dimension columns have been investigated and their performances to achieve (i) a group type separation of hydrocarbons and (ii) individual identification and quantitation of fatty acid ester blend with diesel are reported and discussed. Finally, comparison of quantitative GC x GC results with reference methods demonstrates the benefits of GC x GC approach which enables fast and reliable individual quantitation of fatty acid esters in one single run. Results show that under developed chromatographic conditions, quantitative group type analysis of hydrocarbons is also possible, meaning that simultaneous quantification of hydrocarbons and fatty acid esters can be achieved in one single run.     

Regio- and chemoselective magnesiation of protected uracils and thiouracils using TMPMgCl x LiCl and TMP(2)Mg x 2 LiCl

Two successive regio- and chemoselective magnesiations using TMPMgCl x LiCl and TMP(2)Mg x 2 LiCl enable the full functionalization of protected uracils and thiouracils in good to excellent yields.     

Bacterial base excision repair enzyme Fpg recognizes bulky N7-substituted-FapydG lesion via unproductive binding mode

Fpg is a bacterial base excision repair enzyme that removes oxidized purines from DNA. This work shows that Fpg and its eukaryote homolog Ogg1 recognize with high affinity FapydG and bulky N7-benzyl-FapydG (Bz-FapydG). The comparative crystal structure analysis of stable complexes between Fpg and carbocyclic cFapydG or Bz-cFapydG nucleoside-containing DNA provides the molecular basis of the ability of Fpg to bind both lesions with the same affinity and to differently process them. To accommodate the steric hindrance of the benzyl group, Fpg selects the adequate rotamer of the extrahelical Bz-cFapydG formamido group, forcing the bulky group to go outside the binding pocket. Contrary to the binding mode of cFapydG, the particular recognition of Bz-cFapydG leads the BER enzymes to unproductive complexes which would hide the lesion and slow down its repair by the NER machinery.     

Polymer-supported stereoselective synthesis of benzimidazolinopiperazinones

We describe the efficient synthesis of 4,7,8,10-tetrasubstituted-(((4S,10aS)-3-oxo-3,4,10,10a-tetrahydrobenzo[4,5]imidazo[1,2-a]pyrazin-2(1H)-yl)alkyl)amides on solid phase via tandem N-acyliminium ion cyclization-nucleophilic addition reactions. The synthesis proceeded with complete stereocontrol of a newly formed stereogenic center, provided crude material of high purity, and used commercially available building blocks under mild reaction conditions.