Enantioselective Synthesis of <i>anti</i>-β-Substituted γ,δ-Unsaturated Amino Acids: A Highly Selective Asymmetric Thio-Claisen Rearrangement
作者:Zhihua Liu、Hongchang Qu、Xuyuan Gu、Byoung J. Min、Joel Nyberg、Victor J. Hruby
DOI:10.1021/ol801657q
日期:2008.9.18
novel synthesis of optically active anti-beta-substituted gamma,delta-unsaturated amino acids via a thio-Claisenrearrangement has been achieved. A 2,5-diphenylpyrrolidine was used as a C2-symmetric chiral auxiliary to control the stereochemistry, giving good yields and excellent diastereoselectivities and enantioselectivities.
Asymmetric Eschenmoser−Claisen Rearrangement for Anti-β-Substituted γ,δ-Unsaturated Amino Acids
作者:Hongchang Qu、Xuyuan Gu、Zhihua Liu、Byoung J. Min、Victor J. Hruby
DOI:10.1021/ol701704h
日期:2007.9.1
synthetic building blocks in organic synthesis and for peptidomimetics. A novel asymmetric Eschenmoser-Claisen rearrangement with use of a C2-symmetric chiral auxiliary was developed to generate this type of amino acid. Excellent diastereoselectivities and high enantioselectivities (87-93% ee) were obtained after the chiral auxiliary was removed via iodolactonization/zinc reduction.
The asymmetric synthesis of beta-substituted alpha-amino acids with use of iridium-catalyzedallylicsubstitution was described. The Ir-catalyzed allylicsubstitution of diphenylimino glycinate with allylic phosphates proceeded smoothly even at 0 degrees C and gave branch products with high enantioselectivity (up to 97% ee), when chiral bidentate phosphite bearing the 2-ethylthioethyl group was employed