87421-20-3Relevant academic research and scientific papers
Diastereo- And enantioselective synthesis of β-Hydroxy-α-amino acids: Application to the synthesis of a key intermediate for lactacystin
Li, Qiong,Yang, Shao-Bo,Zhang, Zhihui,Li, Lei,Xu, Peng-Fei
supporting information; experimental part, p. 1627 - 1631 (2009/09/24)
The development of a highly efficient and stereoselective methodology for the preparation of β-hydroxy-α- amino acids is described. Nucleophilic addition of enolates of tricyclic iminolactones 1a and 1b to aldehydes in the presence of 6 equiv of lithium chloride in THF at -78 °C leads to aldol adducts in good yield (63-86%) and high diastereoselectivity (up to >25:1 dr). Subsequently, hydrolysis of the aldol adducts under acidic conditions leads to the corresponding β-hydroxy-a-amino acids in good yields (up to 83%) and excellent enantiomeric excesses (99% ee) with good recovery yields of the chiral auxiliaries 6 and 7. This methodology was applied to the facile synthesis of the key intermediate for lactacystin along with several isomers.
Asymmetric Syntheses via Heterocyclic Intermediates, XVIII. - On the Enantioselective Synthesis of (2R)-Serine Methyl Esters or (2R)-Serines Starting with the Bis(lactim) Ether of cyclo-(-L-Val-Gly)
Schoellkopf, Ulrich,Groth, Ulrich,Gull, Martin-Reinhold,Nozulak, Joachim
, p. 1133 - 1151 (2007/10/02)
The lithiated bis(lactim) ether 8a furnishes with aldehydes and ketones in good yields the addition products 11 with (3R) configuration.The asymmetric inductions at C-3 of 11 (d.e. values) amount to more than 95 percent with ketones, with aldehydes they are somewhat smaller.With unsymmetrical ketones or aldehydes C-3' also becomes a chiral center.For the (3R)-major diastereomers the "second induction" at C-3' varies from about 4 t about 87 percent (for benzaldehyde or isobutyraldehyde, respectively), preferably the (3R,3'S) epimers are formed. - Acid hydrolysis of 11 yields (besides methyl L-valinate) the (2R)-serine methyl esters 26.Their e.e. values correspond with the d.e. values of 11. - Dehydratation of 11 furnishes the "Hofmann olefins" 32 and/or the "Saytzeff olefins" 33 which can be transformed in various ways into optically active amino acids.
