- Copper complex catalyzed asymmetric monosulfonylation of meso-vic-diols
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Asymmetric desymmetrization of meso-vic-diols was performed by tosylation in the presence of copper(II) triflate and (R,R)-Ph-BOX as a catalyst. The method was successfully applied to asymmetric desymmetrization of cyclic and acyclic meso-vic-diols in hig
- Demizu, Yosuke,Matsumoto, Kazuya,Onomura, Osamu,Matsumura, Yoshihiro
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p. 7605 - 7609
(2008/03/14)
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- The use of benzamide derivatives of secondary amines for stereochemical studies by circular dichroism
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The benzamide chromophore is widely used as a Cottonogenic derivative of primary amines for stereochemical studies by circular dichroism. The assignments based on the exciton chirality method are reliable since the benzamide group has well-defined geometry and conformation. A recent report U.D. Chisholm, J. Golik, B. Krishnan, J.A. Matson, D.L. Van Vranken, J. Am. Chem. Soc. 1999, 121: 3801-3802) claimed a caveat in the application of the exciton chirality method to benzamides derived from secondary amines. By the use of benzoyl derivatives of amino alcohols (1-4) and diamines (5, 6) of known absolute configuration we demonstrate that the 250-210 nm range exciton Cotton effects due to secondary and tertiary benzamides are generally of opposite sign. The origin of such disparity is traced to different conformational equilibria of the amide C-N bond in secondary and tertiary benzamides, as shown by semiempirical molecular modelling and NMR data. This feature can be useful in the determination of absolute configuration by analysis of the CD spectra due to exciton coupling of tertiary benzamides.
- Gawronski, Jacek,Kolbon, Halina,Kwit, Marcin
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- SYNTHESIS OF (L)-DAUNOSAMINE AND RELATED AMINO SUGARS
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1-(2-Furyl)ethanol (6) has been converted into methyl (+/-)-daunosaminide (1) and methyl (+/-)-ristosaminide (3) by use of an intramolecular cyclisation of a trichloroacetimidate group. (+/-)-Daunosamine (1) has been obtained more directly from the alcohol (10) by use of a modified Mitsunobu reaction; the scope of the latter reaction has been explored using cyclohex-2-en-1-ol as a model substrate.Asymmetric reduction of 2-acetylfuran (5) has given (S)-1-(2-furyl)ethanol (46) in good enantiomeric excess, thus providing a short route to the L-enantiomers of the amino sugars (1), (2), and (3) from a cheap, non-carbohydrate precursor.
- Sammes, Peter G.,Thetford, Dean
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p. 111 - 124
(2007/10/02)
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- NEW ROUTES TO CIS-1,2-HYDROXYAMINES AND RELATED SYSTEMS
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Use of modified Mitsunobu reactions followed by intramolecular cyclisations have been used to prepare cis-1,2-hydroxyamines, cis-1,3-hydroxyamines, 1,2,3-dihydroxyamines and 1,2,3-diaminoalcohols from allylic alcohols
- Sammes, Peter G.,Thetford, Dean
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p. 2275 - 2278
(2007/10/02)
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