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
Chiral Proton Catalysis: Enantioselective Brønsted Acid Catalyzed Additions of Nitroacetic Acid Derivatives as Glycine Equivalents
作者:Anand Singh、Ryan A. Yoder、Bo Shen、Jeffrey N. Johnston
DOI:10.1021/ja068073r
日期:2007.3.1
unsymmetrical, bifunctional chiral proton catalyst (2) has been developed to enable the highly diastereo- and enantioselective synthesis of epimerizable addition products from nitroacetic acid esters. The strategy is analogous to O'Donnell's glycine Schiff base alkylations that have been broadly applied to the synthesis of α-amino acids. In this regard, nitroacetic acid esters provide complementary
Dynamic Devices. Shape Switching and Substrate Binding in Ion-Controlled Nanomechanical Molecular Tweezers
作者:Anne Petitjean、Richard G. Khoury、Nathalie Kyritsakas、Jean-Marie Lehn
DOI:10.1021/ja031915r
日期:2004.6.1
As examples of supramolecular devices performing chemical (ionic, molecular) control of binding events and models of related natural systems, two molecular conformational switches are described, which display cation-controlled nanomechanical motion coupled to substrate binding and release. The substrate binding relies on donor/acceptor interactions, provided by intercalation between planar sites located at the extremities of the switching units, whereas cation complexation is responsible for conformational regulation. The terpyridine py-py-py-based receptor is activated toward substrate binding upon complexation of a zinc(II) cation and operates in a two-state process. The replacement of the central pyridine by a 4,6-disubstituted pyridimine as in py-pym-py induces a state reversal and yields a new receptor which binds a substrate in the absence of cation, and releases it when copper(I) is introduced, following a three-step process. These systems represent effector-triggered supramolecular switching devices leading toward multistate nanomechanical chemical systems. These two systems illustrate the use of simple conformational switches in the binding site and allosteric regulation of substrate affinity.
Synthesis of 3,3′‐Di(2‐Pyridyl)‐1,1′‐Bi‐2‐Naphthol Derivatives
A new kind of (S)-3,3'-dipyridyl BINOLs (3a-d) with C-2-symmetry were synthesized in 79-84% yields by Suzuki coupling of the diboronic acid dipinacol ester (S)-1 containing a (S)-binaphthyl group with bromopyridine derivatives (2a-d) followed by hydrolysis.