- Ruthenium-catalyzed asymmetric epoxidation of olefins using H 2O2, part I: Synthesis of new chiral N,N,N,-tridentate pybox and pyboxazine ligands and their ruthenium complexes
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The synthesis of chiral tridentate N,N,N-pyridine-2.6-bisoxazolines 3 (pyhox ligands) and N,N,N-pyridine-2.6-bisoxazines 4 (pyboxazine ligands) is described in detail. These novel ligands constitute a useful tool-box for the application in asymmetric catalysis. Compounds 3 and 4 are conveniently prepared by cyclization of enantiomerically pure α- or β-amino al cohols with dimethyl pyridine-2,6-dicarboximidate. The corresponding ruthenium complexes are efficient asymmetric epoxidation catalysts and have been prepared in good yield and fully char acterized by spectroscopic means. Four of these ruthenium complexes have been characterized by X-ray crystallography. For the first time the molecular structure of a pyboxazine complex (2,6-bis-[(4S)-4-phenyl-5,6- dihydro-4H-[1,3]oxazinyl]pyridine)(pyridine-2,6-dicarboxylate)ruthenium (S)-2aa, is presented.
- Tse, Man Kin,Bhor, Santosh,Klawonn, Markus,Anilkumar, Gopinathan,Jiao, Haijun,Doebler, Christian,Spannenberg, Anke,Magerlein, Wolfgang,Hugl, Herbert,Beller, Matthias
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p. 1855 - 1874
(2008/02/02)
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- SYNTHESIS OF 6-ARYL-4-HYDROXYPIPERIDIN-2-ONES AND A POSSIBLE APPLICATION TO THE SYNTHESIS OF A NOVEL HMG-CoA REDUCTASE INHIBITOR
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A series of 6-aryl-4-hydroxypiperidin-2-ones (11a-11g) were synthesised with the key step being a Dieckmann cyclisation of the appropriate methyl 3-(ethoxycarbonylacetylamino)-3-(substituted) propionate (8a-8g) and this new synthetic route was successfully applied to the synthesis of 4-hydroxy-6-(2-phenylethyl)piperidin-2-one (11h).The application of this strategy to the synthesis of the putative HMG-CoA reductase inhibitor 6--4-hydroxypiperidin-2-one (11i) was attempted, but failed during the Dieckmann cyclisation of methyl 3-(ethoxycarbonylacetylamino)- 3-propionate (8i).An alternative synthesis of a 1:1 diastereomeric mixture of (11i) was achieved by the reductive cleavage of the isoxazoline (24) with Raney nickel.The mixture of diastereoisomers (11i) was inactive in-vitro and in-vivo (rat) against HMG-CoA reductase
- Ashton, Michael J.,Hills, Susan J.,Newton, Christopher G.,Taylor, John B.,Tondu, Sylvie C. D.
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p. 1015 - 1035
(2007/10/02)
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