2-Alkyl-substituted lactams 4 were synthesized in good overall yields and high enantiomeric purities (ee =71-99%) by α-alkylation of chiral N-(dialkylamino)lactams 2 and subsequent reductive N-N bond cleavage of the resulting lactams 3 with lithium in liquid ammonia. The lactams 2, in turn, were prepared in good yields by cyclization of Ï-chloroalkanohydrazides 1 with sodium hydride. Acidic hydrolysis of lactams 4 leads to γ-aminobutanoic acid (GABA) derivatives 5 (ee ≥ 99%). The absolute configuration was determined by polarimetry and an X-ray structure analysis of (S,S)-3e’.
Peptide Catalyzed Asymmetric Conjugate Addition Reactions of Aldehydes to Nitroethylene—A Convenient Entry into γ<sup>2</sup>-Amino Acids
作者:Markus Wiesner、Jefferson D. Revell、Sandro Tonazzi、Helma Wennemers
DOI:10.1021/ja801027s
日期:2008.4.1
The peptide H-D-Pro-Pro-Glu-NH2 is a highly effective catalyst for conjugateadditionreactions between aldehydes and nitroethylene. Only 1 mol % of H-d-Pro-Pro-Glu-NH2 and a 1.5-fold excess of aldehyde with respect to nitroethylene suffice to obtain gamma-nitroaldehydes and, after reduction, monosubstituted gamma-nitroalcohols in excellent yields and optical purities. The products can be readily converted