A new efficient route for multigram asymmetric synthesis of alkannin and shikonin

A short and convergent approach for the synthesis of alkannin, shikonin and shikalkin is presented. A Hauser-type annulation of cyanophthalide 26 with enone 7 affords the complete aromatic system in just one step with concomitant attachment of the entire side chain. Subsequent Corey's oxazaborolidine mediated asymmetric reduction of the above advanced intermediate, leads to the required isomer in high enantiomeric excess. Finally, a selective and high yielding deprotection protocol furnishes the title compounds as pure crystalline precipitates. Thus, a multigram synthesis of shikonin, alkannin and shikalkin is achieved in high yield and enantioselectivity.     

A General Procedure for the Efficient Synthesis of (Alkylamino)naphthoquinones

Alkylamino derivatives of naphthazarine, juglone, and naphthoquinone have been synthesized via their corresponding bromo-analogues, in high yields, especially in the case of naphthazarins.     

Electrochemical testing practices of environmentally friendly aerospace coatings for corrosion performance assessment

Hexavalent chromium has been successfully employed for corrosion protection purposes in aerospace coatings for decades. However, legislation will restrict the use of Cr⁶⁺ in the future and therefore the aerospace sector needs to identify alternative environmentally friendly coatings for corrosion protection. Before implementation of newly developed systems into actual components is possible, rigorous and time-consuming testing practices are required to ensure the new systems can achieve the strict aerospace standards requirements. The emerging number of coating systems being developed, and the vast research conducted on the subject worldwide, make the selection of suitable replacements for industrial application challenging. In this work, differently pretreated aluminium AA2024 alloy surfaces are coated with conventional Cr⁶⁺ containing coating and compared with a number of industrial alternative coatings. Corrosion performance is assessed by real-time imaging while immersed, by electrochemical impedance spectroscopy (EIS), and by standardised salt-spray testing (SST). Results reveal that the performance ranking acquired by SST can be readily replaced by short-term immersion tests, and the time to failure in SST can be estimated from key corrosion indicators arising from EIS measurements at specific immersion times.     

Effects of Sideritis euboea (Lamiaceae) aqueous extract on IL-6, OPG and RANKL secretion by osteoblasts

The water extract obtained from the aerial parts of Sideritis euboea (Lamiaceae), which is known in Greece as 'mountain tea', was investigated by determining the in vitro effect of this extract on the IL-6, OPG and RANKL secretion by osteoblasts, three important molecules in osteoblast-osteoclast interplay. The results showed that this extract reduced significantly the secretion of IL-6 by KS-483 osteoblasts, while it also suppressed RANKL secretion, with both effects being dose-dependent and more potent at the higher concentrations tested (50, 100 microg/mL). We further determined the chemical profile of the extract by applying an analytical U-HPLC-DAD-ESI-MS/MS method using the high resolution hybrid LTQ-Orbitrap Discovery spectrometer. An ESI source in negative mode was employed. The analysis indicated that the water extract of S. euboea is rich in flavonoid glycosides, and phenylpropanoid glycosides.