Chiral lithium amido sulfide ligands for asymmetric addition reactions of alkyllithium reagents to aldehydes
Six chiral amino sulfides have been synthesised from the amino acids phenylalanine, phenylglycine and valine. These amino sulfides were used as chiral ligands in the asymmetric addition of n-butyllithium and metyllithium to various aldehydes at low temperatures. The highest stereoselectivities were obtained with benzaldehyde, resulting in 1-phenyl-1-pentanol and 1-phenyl-1-ethanol in enantiomeric excesses of >98.5 and 95%, respectively. These stereoselectivities were significantly higher than those induced by the ether analogues.
Granander, Johan,Sott, Richard,Hilmersson, Goeran
p. 439 - 447
(2007/10/03)
New chiral auxiliaries for the construction of quaternary stereocenters by copper-catalyzed Michael reactions
The construction of quaternary stereocenters with 95-99% ee at ambient temperatures can be achieved by a copper-catalyzed Michael reaction with the application of α-amino acid amides as chiral auxiliaries [Eq. (1)]. These amides can be obtained in a few steps from the α-amino acids with standard transformations and, after the Michael reaction, they can be quantitatively recovered. Exclusion of water and oxygen is not necessary.
Christoffers, Jens,Mann, Alexander
p. 2752 - 2754
(2007/10/03)
Conversion of chiral amino acids to enantiomerically pure α-methylamines
Enantiomerically enriched α-methylamines are obtained in high yield by Raney nickel reduction of N-Boc-protected, amino acid-derived thioethers.
Donner
p. 1223 - 1226
(2007/10/02)
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