Chiral Ammonium Betaines: A Bifunctional Organic Base Catalyst for Asymmetric Mannich-Type Reaction of α-Nitrocarboxylates
作者:Daisuke Uraguchi、Kyohei Koshimoto、Takashi Ooi
DOI:10.1021/ja8041004
日期:2008.8.1
A chiralammoniumbetaine, an intramolecular ion-pairing quaternary ammonium aryloxide 3, has been designed and its vast potential as an enantioselective organic base catalyst has been successfully demonstrated in the highly enantioselective direct Mannich-type reaction of alpha-substituted alpha-nitrocarboxylates 2 with various N-Boc imines 1. The present study provides a conceptually new approach
A Bench-Stable Homodinuclear Ni<sub>2</sub>−Schiff Base Complex for Catalytic Asymmetric Synthesis of α-Tetrasubstituted <i>anti</i>-α,β-Diamino Acid Surrogates
Catalyticasymmetric direct Mannich-type reactions of α-substituted nitroacetates using a new bench-stable homodinuclear Ni2−Schiff base 1b complex are described. The Ni2−1b complex gave Mannich products, precursors for anti-α,β-diamino acids with an α-tetrasubstituted carbon stereocenter, in >99−91% ee. The Ni2−1b complex was also applicable to direct Mannich-type reactions of malonates and β-keto
A Diastereo- and Enantioselective Synthesis of α-Substituted <i>syn</i>-α,β-Diamino Acids
作者:Anand Singh、Jeffrey N. Johnston
DOI:10.1021/ja8011808
日期:2008.5.1
Highly diastereo- and enantioselective additions of substituted alpha-nitroesters to imines have been developed. High diastereoselection relies on the finding that the combination of chiral proton catalyst 2b and alpha-nitro aryl esters bearing 2,6-disubstitution combine to raise substrate-controlled diastereoselection to >20:1 in favor of the syn diastereomer. Furthermore, the chiral catalyst provides
3, 5-disubstituted and 3, 4, 5-trisubstituted 2-isoxazolines and
申请人:Hoechst Aktienegesellschaft
公开号:US05814627A1
公开(公告)日:1998-09-29
A compound having the formula (I), a physiologically tolerable salt of the compound having the formula (I) and/or a steroisomeric form of the compound having the formula (I), in which one residue R.sup.1 or R.sup.2 stands for the formula (II), are suitable for preparing medicaments for the therapy of inflammations, asthma, rheumatoid diseases and auto-immune diseases.
Enantioselective Synthesis of Quaternary α-Amino Acids Enabled by the Versatility of the Phenylselenonyl Group
作者:Antonin Clemenceau、Qian Wang、Jieping Zhu
DOI:10.1002/chem.201604781
日期:2016.12.19
conjugate addition of α‐alkyl substituted α‐nitroacetates to phenyl vinyl selenone was developed. The resulting enantio‐enriched α,α‐dialkyl substituted α‐nitroacetates were subsequently converted to various cyclic and acyclic quaternary α‐amino acids, taking advantage of the rich functionalities of the resulting Michael adducts. Novel protocols allowing chemoselective reduction of phenyl selenone to