- Efficient pseudo-enantiomeric carbohydrate olefin ligands
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Highly efficient pseudo-enantiomeric olefin ligands were designed from d-glucose and d-galactose. These ligands yield consistently excellent levels of enantioselectivity in Rh(I)-catalyzed 1,4-additions of aryl- and alkenylboronic acids to achiral enones and high diastereoselectivity with chiral substrates. Contrary to established olefin ligands, they are obtained enantiomerically pure via short syntheses without racemic resolution steps, making them a valuable addition to the arsenal of chiral ligands with olefinic donor sites.
- Grugel, Holger,Albrecht, Fabian,Minuth, Tobias,Boysen, Mike M. K.
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p. 3780 - 3783
(2012/09/08)
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- Amine-linked diglycosides: Synthesis facilitated by the enhanced reactivity of allylic electrophiles, and glycosidase inhibition assays
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Diglycose derivatives, consisting of two monosaccharides linked at non-anomeric positions by a bridging nitrogen atom, have been synthesised. Conversion of one of the precursor monosaccharide coupling components into an unsaturated derivative enhances its
- Cumpstey, Ian,Frigell, Jens,Pershagen, Elias,Akhtar, Tashfeen,Moreno-Clavijo, Elena,Robina, Inmaculada,Alonzi, Dominic S.,Butters, Terry D.
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supporting information; experimental part
p. 1115 - 1123
(2011/10/08)
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- The design and synthesis of novel anomeric hydroperoxides: Influence of the carbohydrate residue in the enantioselective epoxidation of quinones
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We present a study of the base (DBU)-catalysed epoxidation of a number of important naturally occurring quinones using a series of pyranose-derived anomeric hydroperoxides. The absolute (viz. d or l) stereochemistry of the carbohydrate, electronic nature of the 6-substituent and ring substitution are all important variables, both for the formation of the hydroperoxide and its reactivity. Reactions studied were the epoxidation of a precursor of the natural antibiotic, alisamycin and a series of naphthoquinones related to Vitamin K. In the best case, an ee of 82% was obtained; either product enantiomer is accessible according to the absolute stereochemistry of the carbohydrate. Finally, a molecular modelling study of the reaction is reported, concluding that the reactions are under kinetic control and that the observed ees cannot be explained by considering transition states that involve only the quinone and peroxide anion. It seems likely that the DBU molecule may play a key role in the transition state.
- Bundu, Abass,Berry, Neil G.,Gill, Christopher D.,Dwyer, Catherine L.,Stachulski, Andrew V.,Taylor, Richard J.K.,Whittall, John
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p. 283 - 293
(2007/10/03)
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