- A novel stereoselective tin-free radical protocol for the enantioselective synthesis of pyrrolidinones and its application to the synthesis of?biologically active GABA-derivatives
-
Optically pure 4-alkyl-pyrrolin-2-ones were synthesized from chiral N-allyl-α-bromoacetamides in high selective and stereo-controlled fashion, via a sequential 5-exo-trig radical cyclization-hydrogen or bromine atom-transfer process, under non-tin conditi
- Rodríguez-Soria, Verónica,Quintero, Leticia,Sartillo-Piscil, Fernando
-
p. 2750 - 2754
(2008/09/19)
-
- Application of polymer-supported enzymes and reagents in the synthesis of γ-aminobutyric acid (GABA) analogues
-
Polymer-supported pig liver esterase was used for the resolution of meso-diesters. The enzyme can be recovered quantitatively from the reaction mixture by filtration and reused without significant loss of activity. Further transformation of the resulting enantiomerically enriched carboxylic acids through the application of polymer-supported reagents and scavengers provides a number of GABA-analogues.
- Baxendale, Ian R.,Ernst, Martin,Krahnert, Wolf-Rüdiger,Ley, Steven V.
-
p. 1641 - 1644
(2007/10/03)
-
- Resolution and conformational analysis of diastereoisomeric esters of cis- and trans-2-(aminomethyl)-1-carboxycyclopropanes
-
(1R,2S)-, (1S,2R)-, (1R,2R)- and (1S,2S)-2-(Aminomethyl)-1- carboxycyclopropanes, conformationally restricted analogues of the neurotransmitter γ-aminobutyric acid (GABA), have been resolved by chromatographic separation of the corresponding diastereoisomeric esters which were formed between the cis- and trans-2-(acetamidomethyl)1- carboxycyclopropanes with (R)-(-)-pantolactone. 1H NMR, semi-empirical conformational analysis, ab initio (DFT) structure and NMR shielding tensor calculations of the cis-diastereoisomers allowed the absolute configuration assignments of the cis-amino acids.
- Duke, Rujee K.,Allan, Robin D.,Chebib, Mary,Greenwood, Jeremy R.,Johnston, Graham A. R.
-
p. 2533 - 2548
(2007/10/03)
-
- An Efficient Route to GABA-Analogous Amino Acids: Cyclopropanation of N-Silylated Allylamines and Enamines
-
N-Silylated allylamines 1 are effectively transformed into methyl cyclopropanecarboxylates 2 by methyl diazoacetate under Rh2(OAc)4 catalysis.Derivatives 2a and 2b are smoothly converted into trans-substituted amino acids 6a and 6b, respectively, and to bicyclic γ-lactams 5a and 5b.The pharmacologically interesting γ-aminobutyric acid (GABA) analogue trans-6a is now available in few steps.Photochemical and thermal Fe(CO)5-induced hydrogen shift converts allylamine derivatives 1 into N-silylated enamines 7.While enamine (E)-7a can be cyclopropanated with methyl diazoacetate under Cu(acac)2 catalysis to afford the desired cyclopropane derivatives 8a in good yield, the other enamines are rather unreactive towards the carbenoid.Use of an optically active catalyst provides 8a with an ee of 56percent (cis) and 20percent (trans).Acid induced ring cleavage of 8a gives the β-formyl ester 10a, and reduction of 8a followed by desilylation provides the aminocyclopropane 14 in good overall yield, thus demonstrating that cyclopropanes like 8a can serve as useful synthetic intermediates. --- Key Words: Amino acids / GABA analogues / Aminocyclopropanes / Enamines, N-silylated / Cycloaddition
- Paulini, Klaus,Reissig, Hans-Ulrich
-
p. 455 - 461
(2007/10/02)
-
- Synthesis of &γ-Aminobutyric Acid Analogue of Restricted Conformation. Part 1. The 2-(Aminomethyl)cycloalkaneacetic Acids
-
The synthesis of analogues with restricted rotatin about the C(2)-C(3) bond of γ-aminobutyric acid, namely cis- and trans-2-(aminomethyl)-cyclopropane and -cyclobutanecarboxylic acids and trans-2-(aminomethyl)cyclohexanecarboxylic acid are described.
- Kennewell, Peter D.,Matharu, Saroop S.,Taylor, John B.,Westwood, Robert,Sammes, Peter G.
-
p. 2563 - 2570
(2007/10/02)
-