- Use of N-trifluoroacetyl-protected amino acid chlorides in peptide coupling reactions with virtually complete preservation of stereochemistry
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The use of protected amino acid chlorides for peptide coupling reactions has long been avoided due to the extensive racemization that commonly occurs during either the acid chloride formation or the coupling reaction itself. Conditions are described which
- Jass, Paul A.,Rosso, Victor W.,Racha, Saibaba,Soundararajan, Nachimuthu,Venit, John J.,Rusowicz, Andrew,Swaminathan, Shankar,Livshitz, Julia,Delaney, Edward J.
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p. 9019 - 9029
(2007/10/03)
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- A parallel preparation of a bicyclic N-chiral amine library and its use for chiral catalyst screening
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A parallel library of optically active bicyclic tertiary amines bearing N-chiral bridgehead nitrogen atoms was readily prepared by condensation of primary amines, cyclic amino acids and aldehydes. The enantiocontrolling ability of each of the library members was examined for the asymmetric alkylation of benzaldehyde with diethylzinc, and (3R,6R,7aS)-(2,3-diphenyl-6-hydroxy)hexahydro-1H-pyrrolo[1,2-c]imidazol-1- one, which contains a β-amino alcohol unit, showed high enantioselectivity.
- Uozumi, Yasuhiro,Mizutani, Kanako,Nagai, Shin-ichi
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p. 407 - 410
(2007/10/03)
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- Rearrangement of ammonium ylides produced by intramolecular reaction of catalytically generated metal carbenoids. Part 2. Stereoselective synthesis of bicyclic amines
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Ammonium ylides produced by intramolecular reaction of copper carbenoids tethered to cyclic allylic amines undergo [2,3]-rearrangement to deliver bicyclic amines. The reaction can be performed using a cyclic N-allylamine in which the diazo group is tethered adjacent to nitrogen, or a vinyl-substituted cyclic amine in which the diazo group is N-tethered to the ring. In the former type of reaction, stereoselective ylide formation and rearrangement usually delivers high levels of diastereocontrol. In the latter case, efficient 'chirality transfer' can be accomplished when the reaction is performed using an enantiomerically pure substrate. The reactions have been used to construct pyrrolizidine, indolizidine and quinolizidine systems, and the CE sub-unit found in the manzamine and ircinal alkaloids.
- Clark,Hodgson,Goldsmith,Blake,Cooke,Street
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p. 3325 - 3337
(2007/10/03)
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- Conformational analysis of 4-amido-2,4-dimethylbutyric acid derivatives
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Both syn- and anti-4-amido-2,4-dimethylbutyric acid derivatives 5 and 6 were found to populate a conformation in which the amido group is gauche to the main chain of the molecule. In the anti series (6) a single conformation predominates, in which the acid carbonyl group is also gauche to the main chain. In the syn series (5) two local conformers prevail about the C-2-C-3 bond.
- Hoffmann, Reinhard W.,Caturla, Francisco,Lazaro, Miguel A.,Framery, Eric,Bernabeu, M. Carmen,Valancogne, Ingrid,Montalbetti, Christian A. G. N.
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p. 187 - 194
(2007/10/03)
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- Enantioselective synthesis of binaphthol derivatives by oxidative coupling of naphthol derivatives catalyzed by chiral diamine-copper complexes
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A highly efficient process of aerobic oxidative coupling of 2-naphthol derivatives catalyzed by 1 mol % of Cu(OH)Cl·TMEDA has been developed. Enantioselective oxidative coupling of naphthols was achieved by the use of 10 mol % of chiral catalysts prepared from proline-derived diamines and cuprous chloride, affording the corresponding binaphthols in good enantioselectivities of up to 78% ee. The ester moiety at the 3-position of the substrate was found to be essential for the good asymmetric induction observed in the present coupling reaction.
- Nakajima, Makoto,Miyoshi, Irie,Kanayama, Kumiko,Hashimoto, Shun-Ichi,Noji, Masahiro,Koga, Kenji
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p. 2264 - 2271
(2007/10/03)
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- α-Amino ketones derived from L-proline, as precursors for isomitosanes and mitosenes
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2-Benzoyl- and 2-(2-naphthoyl)pyrrolidines which can be viewed as aryl α-amino ketones, have been prepared from L-proline via Grignard reactions, bromo-to-lithium exchange, or by Friedel-Crafts acylations.It was impossible to convert the ketone function o
- Orlemans, E. O. M.,Verboom, W.,Lammerink, B. H. M.,Reinhoudt, D. N.
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