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Bajpe S.R.,U-Systems | Kirschhock C.E.A.,U-Systems | Aerts A.,U-Systems | Breynaert E.,U-Systems | And 4 more authors.
Chemistry - A European Journal | Year: 2010

(Figure presented) The molecular steps involved in the self-assembly of Cu3(BTC)2 (BTC=1,3,5-benzenetricarboxylic acid) metal-organic frameworks that enclose Keggin-type H3PW 12O40 heteropolyacid molecules were unraveled by using solution 17O, 31P, and 183WNMR spectroscopy, small-angle X-ray scattering, near-IR spectroscopy, and dynamic light scattering. In aqueous solution, complexation of Cu2+ ions with Keggin-type heteropolyacids was observed. Cu2+ ions are arranged around the Keggin structure so that linking through benzenetricarboxylate groups results in the formation of the Cu3(BTC)2 MOF structure HKUST-1. This is a unique instance in which a templating mechanism that relies on specific molecular-level matching and leads to explicit nanoscale building units can be observed in situ during formation of the synthetic nanoporous material. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA.

Thomas J.,Molecular Design and Synthesis | Goyvaerts V.,Molecular Design and Synthesis | Liekens S.,Rega Institute for Medical Research | Dehaen W.,Molecular Design and Synthesis
Chemistry - A European Journal | Year: 2016

Functionalized 1,2,3-triazole heterocycles have been known for a long time and hold an extraordinary potential in diverse research areas ranging from medicinal chemistry to material science. However, the scope of therapeutically important 1-substituted 4-acyl-1H-1,2,3-triazoles is much less explored, probably due to the lack of synthetic methodologies of good scope and practicality. Here, we describe a practical and efficient one-pot multicomponent reaction for the synthesis of α-ketotriazoles from readily available building blocks such as methyl ketones, N,N-dimethylformamide dimethyl acetal, and organic azides with 100 % regioselectivity. This reaction is enabled by the in situ formation of an enaminone intermediate followed by its 1,3-dipolar cycloaddition reaction with an organic azide. We effectively utilized the developed strategy for the derivatization of various heterocycles and natural products, a protocol which is difficult or impossible to realize by other means. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Ceunen S.,British Petroleum | Wim D.B.,Molecular Design and Synthesis | Compernolle F.,Molecular Design and Synthesis | Mai A.H.,Molecular Design and Synthesis | Geuns J.M.C.,British Petroleum
Carbohydrate Research | Year: 2013

The rare Mexican species Stevia phlebophylla A. Gray was long considered to be the only known Stevia species, beside the well-known S. rebaudiana, containing the highly sweet diterpenoid steviol glycosides. We report a re-evaluation of this claim after phytochemically screening leaves obtained from two herbarium specimens of S. phlebophylla for the presence of steviol glycosides. Despite extensive MS analyses, no steviol glycosides could be unambiguously verified. Instead, the main chromatographic peak eluting at retention times similar to those of steviol glycosides was identified as a new compound, namely 16βhydroxy-17-acetoxy-ent-kauran-19-oic acid-(6-O-β-D-xylopyranosyl-β-D-glucopyranosyl) ester (1) on the basis of extensive NMR and MS data as well as the characterization of its acid hydrolysate. Seven more compounds were detected by ESIMS which are possibly structurally related to 1. It can therefore be concluded that S. phlebophylla is unlikely to contain significant amounts of steviol glycosides, if any. © 2013 Elsevier Ltd.

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